1,054 research outputs found

    Aeolianite and barrier dune construction spanning the last two glacial-interglacial cycles from the southern Cape coast, South Africa

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    The southern Cape region of South Africa has extensive coastal aeolianites and barrier dunes. Whilst previously reported, limited knowledge of their age has precluded an understanding of their relationship with the climatic and sea-level fluctuations that have taken place during the Late Quaternary. Sedimentological and geomorphological studies combined with an optical dating programme reveal aeolianite development and barrier dune construction spanning at least the last two glacial–interglacial cycles. Aeolianite deposition has occurred on the southern Cape coast at ca 67–80, 88–90, 104–128, 160–189 and >200 ka before the present. Using this and other published data coupled with a better understanding of Late Quaternary sea-level fluctuations and palaeocoastline configurations, it is concluded that these depositional phases appear to be controlled by interglacial and subsequent interstadial sea-level high stands. These marine transgressions and regressions allowed onshore carbonate-rich sediment movement and subsequent aeolian reworking to occur at similar points in the landscape on a number of occasions. The lack of carbonates in more recent dunes (Oxygen Isotope Stages 1/2 and 4/5) is attributed not to leaching but to changes to carbonate production in the sediment source area caused by increased terrigenous material and/or changes in the balance between the warm Agulhas and nutrient-rich Benguela ocean current

    Initial Severity and Antidepressant Benefits: A Meta-Analysis of Data Submitted to the Food and Drug Administration

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    Kirsch and colleagues show that, in antidepressant trials, there is a greater difference in efficacy between drug and placebo amongst more severely depressed patients. However, this difference seems to result from a poorer response to placebo amongst more depressed patients

    Weather on the Nearest Brown Dwarfs: Resolved Simultaneous Multi-Wavelength Variability Monitoring of WISE J104915.57-531906.1AB

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    We present two epochs of MPG/ESO 2.2m GROND simultaneous 6-band (rizJHKr'i'z'JHK) photometric monitoring of the closest known L/T transition brown dwarf binary WISE J104915.57-531906.1AB. We report here the first resolved variability monitoring of both the T0.5 and L7.5 components. We obtained 4 hours of focused observations on the night of UT 2013-04-22, as well as 4 hours of defocused (unresolved) observations on the night of UT 2013-04-16. We note a number of robust trends in our light curves. The rr' and ii' light curves appear to be anticorrelated with zz' and HH for the T0.5 component and in the unresolved lightcurve. In the defocused dataset, JJ appears correlated with zz' and HH and anticorrelated with rr' and ii', while in the focused dataset we measure no variability for JJ at the level of our photometric precision, likely due to evolving weather phenomena. In our focused T0.5 component lightcurve, the KK band lightcurve displays a significant phase offset relative to both HH and zz'. We argue that the measured phase offsets are correlated with atmospheric pressure probed at each band, as estimated from 1D atmospheric models. We also report low-amplitude variability in ii' and zz' intrinsic to the L7.5 component.Comment: 14 pages, 5 figures, accepted to ApJ Letter

    Tetra­kis(1,2-dimethoxy­ethane-κ2 O,O′)ytterbium(II) bis­(μ2-phenyl­selenolato-κ2 Se:Se)bis­[bis­(phenyl­selenolato-κSe)mercurate(II)]

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    The title salt, [Yb(C4H10O2)4][Hg2(C6H5Se)6], consists of eight-coordinate homoleptic [Yb(DME)4]2+ dications (DME is 1,2-dimethoxy­ethane) countered with [Hg2(SePh)6]2− di­anions. The cations and anions have twofold rotation and inversion symmetry, respectively. The Yb centre displays a square-anti­prismatic coordination geometry and the Hg centre has a distorted tetra­hedral coordination environment. One phenyl­selenolate anion and one methyl group of a DME ligand are disordered over two positions with equal occupancies. This structure is unique in that it represents a less common mol­ecular lanthanide species in which the lanthanide ion is not directly bonded to an anionic ligand. There are no occurrences of the [Hg2(SePh)6]2− dianion in the Cambridge Structural Database (Version of November 2007), but there are similar oligomeric and polymeric Hgx(SePh)y species. The crystal structure is characterized by alternating layers of cations and anions stacked along the c axis

    A Search for Variability in Exoplanet Analogues and Low-Gravity Brown Dwarfs

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    We report the results of a JJ-band survey for photometric variability in a sample of young, low-gravity objects using the New Technology Telescope (NTT) and the United Kingdom InfraRed Telescope (UKIRT). Surface gravity is a key parameter in the atmospheric properties of brown dwarfs and this is the first large survey that aims to test the gravity dependence of variability properties. We do a full analysis of the spectral signatures of youth and assess the group membership probability of each target using membership tools from the literature. This results in a 30 object sample of young low-gravity brown dwarfs. Since we are lacking in objects with spectral types later than L9, we focus our statistical analysis on the L0-L8.5 objects. We find that the variability occurrence rate of L0-L8.5 low-gravity brown dwarfs in this survey is 308+16%30^{+16}_{-8}\%. We reanalyse the results of Radigan 2014 and find that the field dwarfs with spectral types L0-L8.5 have a variability occurrence rate of 114+13%11^{+13}_{-4}\%. We determine a probability of 98%98\% that the samples are drawn from different distributions. This is the first quantitative indication that the low-gravity objects are more likely to be variable than the field dwarf population. Furthermore, we present follow-up JSJ_S and KSK_S observations of the young, planetary-mass variable object PSO 318.5-22 over three consecutive nights. We find no evidence of phase shifts between the JSJ_S and KSK_S bands and find higher JSJ_S amplitudes. We use the JSJ_S lightcurves to measure a rotational period of 8.45±0.05 8.45\pm0.05~hr for PSO 318.5-22.Comment: accepted for publication in MNRA

    3d-4f heterometallic complexes by the reduction of transition metal carbonyls with bulky Ln(II) amidinates

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    The redox chemistry between divalent lanthanide complexes bearing bulky amidinate ligands has been studied with 3d transition metal carbonyl complexes (iron and cobalt). The reaction of [(DippForm)(2)Sm-II(thf)(2)] (DippForm = N,N '-bis(2,6-diisopropylphenyl)formamidinate) with [Co-2(CO)(8)] resulted in the formation of a tetranuclear Sm-Co complex, [{(DippForm)(2)Sm-III(thf)}(2){(mu-CO)(2)Co(CO)(2)}2]. The product of the reaction of [(DippForm)(2)Yb-II(thf)(2)] and [Co-2(CO)(8)] gives the dinuclear Yb-Co complex [{(DippForm)(2)Yb-III(thf)}{(mu-CO)Co(CO)(3)}] in toluene. The reaction of [(DippForm)(2)Sm-II(thf)(2)] was also carried with the neighbouring group 8 carbonyl complexes [Fe-2(CO)(9)] and [Fe-3(CO)(12)], resulting in a pentanuclear Sm-III-Fe complex, [{(DippForm)(2)Sm-III}(2){(mu(3)-CO)(2)Fe-3(CO)(9)}], featuring a triangular iron carbonyl cluster core

    ‘I will not be thrown out of the country because I’m an immigrant’: Eastern European migrants’ responses to hate crime in a semi-rural context in the wake of Brexit

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    This article examines Eastern European migrants’ experiences of and responses to hate crime. Following the UK European Union Membership Referendum (‘Brexit’ vote), there was an increase in reported hate crimes against immigrants. The study focuses on the experiences of migrants in Lincolnshire, a region of England which has a significant migrant population, and which had one of the highest ‘leave’ votes. The focus on white migrants in this semi-rural setting offers an original perspective in the field of hate crime studies. We draw on semi-structured interviews and observations to identify temporal, spatial, and relational factors in responses to hate crime. We uncover the insecure occupation of a ‘third space’ constituted by material, discursive, and emotional practices. This positioning was destabilised post referendum; but there was also evidence of the operation of agency within processes of ‘othering’, suggesting a transition from victim identity to emergent political subject

    ‘I will not be thrown out of the country because I’m an immigrant’: Eastern European migrants’ responses to hate crime in a semi-rural context in the wake of Brexit

    Get PDF
    This article examines Eastern European migrants’ experiences of and responses to hate crime. Following the UK European Union Membership Referendum (‘Brexit’ vote), there was an increase in reported hate crimes against immigrants. The study focuses on the experiences of migrants in Lincolnshire, a region of England which has a significant migrant population, and which had one of the highest ‘leave’ votes. The focus on white migrants in this semi-rural setting offers an original perspective in the field of hate crime studies. We draw on semi-structured interviews and observations to identify temporal, spatial, and relational factors in responses to hate crime. We uncover the insecure occupation of a ‘third space’ constituted by material, discursive, and emotional practices. This positioning was destabilised post referendum; but there was also evidence of the operation of agency within processes of ‘othering’, suggesting a transition from victim identity to emergent political subject
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