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  • 1
    Publication Date: 2015-12-18
    Description: In recent years, a growing zoo of compact stellar systems (CSSs) have been found whose physical properties (mass, size, velocity dispersion) place them between classical globular clusters (GCs) and true galaxies, leading to debates about their nature. Here we present results using a so far underutilized discriminant, their stellar population properties. Based on new spectroscopy from 8–10m telescopes, we derive ages, metallicities, and [α/Fe] of 29 CSSs. These range from GCs with sizes of merely a few parsec to compact ellipticals (cEs) larger than M32. Together with a literature compilation, this provides a panoramic view of the stellar population characteristics of early-type systems. We find that the CSSs are predominantly more metal rich than typical galaxies at the same stellar mass. At high mass, the cEs depart from the mass–metallicity relation of massive early-type galaxies, which forms a continuous sequence with dwarf galaxies. At lower mass, the metallicity distribution of ultracompact dwarfs (UCDs) changes at a few times 10 7 M , which roughly coincides with the mass where luminosity function arguments previously suggested the GC population ends. The highest metallicities in CSSs are paralleled only by those of dwarf galaxy nuclei and the central parts of massive early types. These findings can be interpreted as CSSs previously being more massive and undergoing tidal interactions to obtain their current mass and compact size. Such an interpretation is supported by CSSs with direct evidence for tidal stripping, and by an examination of the CSS internal escape velocities.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 2
    Publication Date: 2004-11-06
    Description: To what extent do we learn from the positive versus negative outcomes of our decisions? The neuromodulator dopamine plays a key role in these reinforcement learning processes. Patients with Parkinson's disease, who have depleted dopamine in the basal ganglia, are impaired in tasks that require learning from trial and error. Here, we show, using two cognitive procedural learning tasks, that Parkinson's patients off medication are better at learning to avoid choices that lead to negative outcomes than they are at learning from positive outcomes. Dopamine medication reverses this bias, making patients more sensitive to positive than negative outcomes. This pattern was predicted by our biologically based computational model of basal ganglia-dopamine interactions in cognition, which has separate pathways for "Go" and "NoGo" responses that are differentially modulated by positive and negative reinforcement.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Frank, Michael J -- Seeberger, Lauren C -- O'reilly, Randall C -- MH069597-01/MH/NIMH NIH HHS/ -- New York, N.Y. -- Science. 2004 Dec 10;306(5703):1940-3. Epub 2004 Nov 4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Psychology and Center for Neuroscience, University of Colorado Boulder, Boulder, CO 80309-0345, USA. frankmj@psych.colorado.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15528409" target="_blank"〉PubMed〈/a〉
    Keywords: Aged ; Antiparkinson Agents/therapeutic use ; Basal Ganglia/*physiopathology ; *Cognition ; Computer Simulation ; Dopamine/*physiology ; Feedback, Psychological ; Female ; Frontal Lobe/physiopathology ; Humans ; *Learning ; Male ; Matched-Pair Analysis ; Middle Aged ; Models, Neurological ; Parkinson Disease/drug therapy/*physiopathology/*psychology ; Probability ; *Reinforcement (Psychology)
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2014-09-19
    Description: Ultra-compact dwarf galaxies are among the densest stellar systems in the Universe. These systems have masses of up to 2 x 10(8) solar masses, but half-light radii of just 3-50 parsecs. Dynamical mass estimates show that many such dwarfs are more massive than expected from their luminosity. It remains unclear whether these high dynamical mass estimates arise because of the presence of supermassive black holes or result from a non-standard stellar initial mass function that causes the average stellar mass to be higher than expected. Here we report adaptive optics kinematic data of the ultra-compact dwarf galaxy M60-UCD1 that show a central velocity dispersion peak exceeding 100 kilometres per second and modest rotation. Dynamical modelling of these data reveals the presence of a supermassive black hole with a mass of 2.1 x 10(7) solar masses. This is 15 per cent of the object's total mass. The high black hole mass and mass fraction suggest that M60-UCD1 is the stripped nucleus of a galaxy. Our analysis also shows that M60-UCD1's stellar mass is consistent with its luminosity, implying a large population of previously unrecognized supermassive black holes in other ultra-compact dwarf galaxies.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Seth, Anil C -- van den Bosch, Remco -- Mieske, Steffen -- Baumgardt, Holger -- den Brok, Mark -- Strader, Jay -- Neumayer, Nadine -- Chilingarian, Igor -- Hilker, Michael -- McDermid, Richard -- Spitler, Lee -- Brodie, Jean -- Frank, Matthias J -- Walsh, Jonelle L -- England -- Nature. 2014 Sep 18;513(7518):398-400. doi: 10.1038/nature13762.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics and Astronomy, University of Utah, 115 South 1400 East, Salt Lake City, Utah 84112, USA. ; Max-Planck Institut fur Astronomie, Konigstuhl 17, D-69117 Heidelberg, Germany. ; European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, 7630355, Chile. ; School of Mathematics and Physics, University of Queensland, St Lucia, Queensland 4072, Australia. ; Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA. ; 1] Max-Planck Institut fur Astronomie, Konigstuhl 17, D-69117 Heidelberg, Germany [2] European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei Munchen, Germany. ; 1] Smithsonian Astrophysical Observatory, 60 Garden Street MS09, Cambridge, Massachusetts 02138, USA [2] Sternberg Astronomical Institute, Moscow State University, 13 Universitetski prospect, Moscow 119992, Russia. ; European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei Munchen, Germany. ; 1] Australian Astronomical Observatory, 105 Delhi Road, Sydney, New South Wales 2113, Australia [2] Department of Physics and Astronomy, Macquarie University, Sydney, New South Wales 2109, Australia. ; University of California Observatories and Department of Astronomy and Astrophysics, University of California, Santa Cruz, California 95064, USA. ; Landessternwarte, Zentrum fur Astronomie der Universitat Heidelberg, Konigsstuhl 12, D-69117 Heidelberg, Germany. ; Department of Astronomy, The University of Texas at Austin, 1 University Station C1400, Austin, Texas 78712, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25230660" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 1993-04-16
    Description: A mobile endogenous transposable element, Tag1, has been identified in the plant Arabidopsis thaliana. Tag1 was found in the nitrate transporter gene, CHL1, of a chlorate-resistant mutant present in a population of plants containing an active maize Ac transposon. Tag1 excises from the chl1 gene producing chlorate-sensitive revertants with Tag1 or Tag1-related elements at different loci. Tag1 and related elements are present in the Landsberg but not Columbia or Wassilewskija ecotypes of Arabidopsis. Thus, Tag1 provides a tool for the insertional mutagenesis of plant genes essential for biological processes of agronomic importance.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Tsay, Y F -- Frank, M J -- Page, T -- Dean, C -- Crawford, N M -- 5T32CA09345-12/CA/NCI NIH HHS/ -- GM 40672/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1993 Apr 16;260(5106):342-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biology, University of California, San Diego, La Jolla 92093-0116.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8385803" target="_blank"〉PubMed〈/a〉
    Keywords: Arabidopsis/drug effects/*genetics/metabolism ; Base Sequence ; Chlorates/pharmacology ; Cloning, Molecular ; DNA/chemistry/genetics ; *DNA Transposable Elements ; Drug Resistance ; *Genes, Plant ; Molecular Sequence Data ; Mutation ; Nitrates/metabolism ; Plants, Genetically Modified
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
    Publication Date: 2007-10-27
    Description: Deep brain stimulation (DBS) of the subthalamic nucleus markedly improves the motor symptoms of Parkinson's disease, but causes cognitive side effects such as impulsivity. We showed that DBS selectively interferes with the normal ability to slow down when faced with decision conflict. While on DBS, patients actually sped up their decisions under high-conflict conditions. This form of impulsivity was not affected by dopaminergic medication status. Instead, medication impaired patients' ability to learn from negative decision outcomes. These findings implicate independent mechanisms leading to impulsivity in treated Parkinson's patients and were predicted by a single neurocomputational model of the basal ganglia.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Frank, Michael J -- Samanta, Johan -- Moustafa, Ahmed A -- Sherman, Scott J -- New York, N.Y. -- Science. 2007 Nov 23;318(5854):1309-12. Epub 2007 Oct 25.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Psychology and Program in Neuroscience, University of Arizona, Tucson, AZ 85721, USA. mfrank@u.arizona.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17962524" target="_blank"〉PubMed〈/a〉
    Keywords: Aged ; Antiparkinson Agents/administration & dosage/*adverse effects/therapeutic use ; Basal Ganglia/physiology ; Conflict (Psychology) ; *Decision Making ; Deep Brain Stimulation/*adverse effects ; Dopamine Agents/administration & dosage/adverse effects/therapeutic use ; Female ; Humans ; Impulsive Behavior/*etiology ; Learning ; Levodopa/administration & dosage/adverse effects/therapeutic use ; Male ; Middle Aged ; Models, Neurological ; Neural Networks (Computer) ; Parkinson Disease/physiopathology/*psychology/*therapy ; Reaction Time ; Reinforcement (Psychology) ; Subthalamic Nucleus/*physiology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
    Publication Date: 2014-05-14
    Description: We present composite spectra constructed from a sample of 242 150 Lyman α (Lyα) forest absorbers at redshifts 2.4 〈 z 〈 3.1 identified in quasar spectra from the Baryon Oscillation Spectroscopic Survey (BOSS) as part of Data Release 9 of the Sloan Digital Sky Survey III. We select forest absorbers by their flux in bins 138 km s –1 wide (approximately the size of the BOSS resolution element). We split these absorbers into five samples spanning the range of flux –0.05 ≤ F 〈 0.45. Tests on a smaller set of high-resolution spectra show that our three strongest absorption samples would probe circumgalactic regions (projected separation 〈300 proper kpc and | v | 〈 300 km s –1 ) in about 60 per cent of cases for very high signal-to-noise ratio. Within this subset, weakening Lyα absorption is associated with decreasing purity of circumgalactic selection once BOSS noise is included. Our weaker two Lyα absorption samples are dominated by the intergalactic medium. We present composite spectra of these samples and a catalogue of measured absorption features from H  i and 13 metal ionization species, all of which we make available to the community. We compare measurements of seven Lyman series transitions in our composite spectra to single line models and obtain further constraints from their associated excess Lyman limit opacity. This analysis provides results consistent with column densities over the range $14.4 \lesssim \log (N_{\rm H\,\small {I}}) \lesssim 16.45$ . We compare our measurements of metal absorption to a variety of simple single-line, single-phase models for a preliminary interpretation. Our results imply clumping on scales down to ~30 pc and near-solar metallicities in the circumgalactic samples, while high-ionization metal absorption consistent with typical IGM densities and metallicities is visible in all samples.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 257 (1998), S. 478-484 
    ISSN: 1617-4623
    Keywords: Key wordsTag1 ; Transposon ; Arabidopsis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Tag1 is an autonomous transposable element (3.3 kb in length) first identified as an insertion in the CHL1 (NRT1) gene of Arabidopsis thaliana. Tag1 has been found in the Landsberg erecta ecotype of A. thaliana but not in Columbia or WS. In this paper, 41 additional ecotypes were examined for the presence of Tag1. Using an internal Tag1 fragment as probe, we found that DNA from 19 of the 41 ecotypes strongly hybridized to Tag1. Almost all of the Tag1-containing ecotypes had only one or two copies of Tag1 per haploid genome, as determined by Southern blot analysis. The only exception, Bf-1 from Bretagny-sur-Orge, France, had four copies. Two ecotypes, Di-G and S96, gave identical Southern blot patterns to that of Landsberg erecta and were subsequently shown to contain Tag1 at the same two positions found in Landsberg erecta (loci designated as Tag1-2 and Tag1-3). Two other ecotypes, Ag-0 and Lo-1, had a Tag1 element located at Tag1-2 but not at Tag1-3. The distance between these two loci was determined to be 0.37 cM. Analysis of DNA from two related species, A. griffithiana and A. pumila, showed that both species contain sequences that hybridize to Tag1 and that could be amplified with an oligonucleotide specific to the terminal inverted repeats of Tag1. These results show that Tag1 and related elements are present, and may be useful for insertional mutagenesis, in many A. thaliana ecotypes and several Arabidopsis species.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Aequationes mathematicae 19 (1979), S. 194-226 
    ISSN: 1420-8903
    Keywords: Primary 39A30 ; Secondary 22A15, 60E05
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Aequationes mathematicae 11 (1974), S. 317-317 
    ISSN: 1420-8903
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Aequationes mathematicae 12 (1975), S. 121-144 
    ISSN: 1420-8903
    Keywords: 39A30 ; 60E05
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
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