36,451 research outputs found
Early Results on Radioactive Background Characterization for Sanford Laboratory and DUSEL Experiments
Measuring external sources of background for a deep underground laboratory at
the Homestake Mine is an important step for the planned low-background
experiments. The naturally occurring -ray fluxes at different levels in
the Homestake Mine are studied using NaI detectors and Monte Carlo simulations.
A simple algorithm is developed to convert the measured -ray rates into
-ray fluxes. A good agreement between the measured and simulated
-ray fluxes is achieved with the knowledge of the chemical composition
and radioactivity levels in the rock. The neutron fluxes and -ray
fluxes are predicted by Monte Carlo simulations for different levels including
inaccessible levels that are under construction for the planned low background
experiments.Comment: 16 pages, 2 figures, and 9 table
Morphology-dependent trends of galaxy age with environment in Abell 901/902 seen with COMBO-17
We investigate correlations between galaxy age and environment in the Abell
901/2 supercluster for separate morphologies. Using COMBO-17 data, we define a
sample of 530 galaxies, complete at on an area of (Mpc/). We explore several age indicators including an
extinction-corrected residual from the colour-magnitude relation (CMR). As a
result, we find a clear trend of age with density for galaxies of all
morphologies that include a spheroidal component, in the sense that galaxies in
denser environments are older. This trend is not seen among Scd/Irr galaxies
since they all have young ages. However, the trend among the other types is
stronger for fainter galaxies. While we also see an expected age-morphology
relation, we find no evidence for a morphology-density relation at fixed age.Comment: Accepted for publication in MNRAS (Letters
Did Covid-19 lead to an increase in hate crime against Chinese people in London?
We examine whether Covid-19, which is widely believed to have originated in China, negatively affected the environment for Chinese people in London leading to an increase in hate crimes towards this group relative to others. With data from the Metropolitan Police for the whole of the Metropolitan area of London we use a difference-in-differences approach to examine what happened to hate crimes against Chinese people in London in the months before (Oct-Dec 2019) and the months after the Covid-19 pandemic (Jan-Mar 2020) relative to other ethnic groups, to other crimes and to other time periods. Our methodology utilises the fact that Covid-19 came as an unexpected shock, which very quickly changed the environment for crime, and did so differentially across ethnicities. We argue that this shock is likely to negatively impact on attitudes and behaviours towards Chinese people, but have no effect on other ethnicities. Our results show that in the months after Covid-19 there was an increase in hate crimes against Chinese people, but this increase was not seen amongst the other ethnic groups, other non-hate crimes, nor in any other time period. This leads us to conclude that Covid-19 lead to an increase in hate crimes against Chinese people in London. That Covid-19 changed behaviour towards Chinese people highlights an intrinsic link between Covid-19 and racism. Unfortunately, the rise in hate crime that we identify adds to a growing list of ways in which ethnic minority groups disproportionately suffered, and continue to do so, during the pandemic
Did the first Covid-19 national lockdown lead to an increase in domestic abuse in London?
On March 23rd 2020, the UK, following close behind a number of other countries went into its first national lockdown in a bid to stop the spread of Covid-19. Boris Johnson told people to stay at home and save lives. But what happens when home isn’t safe? This paper uses data from the Metropolitan Police to examine the impact of the first lockdown on domestic abuse in the 32 boroughs of the London Metropolitan area. Using a before and after approach, and controlling for other factors, we show that domestic abuse crimes rose during lockdown. We find this increase is greater for some crimes and populations than others and is consistent across the whole lockdown period. Once lockdown restrictions are eased, rates decline but remain slightly higher than prior to lockdown up to 3 months later
Environmental dependence of AGN activity in the supercluster A901/2
We present XMM data for the supercluster A901/2, at z ~ 0.17, which is
combined with deep imaging and 17-band photometric redshifts (from the COMBO-17
survey), 2dF spectra and Spitzer 24um data, to identify AGN in the
supercluster. The 90ksec XMM image contains 139 point sources, of which 11 are
identified as supercluster AGN with L_X(0.5-7.5keV) > 1.7x10^41 erg/cm2/s. The
host galaxies have M_R < -20 and only 2 of 8 sources with spectra could have
been identified as AGN by the detected optical emission lines. Using a large
sample of 795 supercluster galaxies we define control samples of massive
galaxies with no detected AGN. The local environments of the AGN and control
samples differ at >98 per cent significance. The AGN host galaxies lie
predominantly in areas of moderate projected galaxy density and with more local
blue galaxies than the control sample, with the exception of one very bright
Type I AGN very near the centre of a cluster. These environments are similar
to, but not limited to, cluster outskirts and blue groups. Despite the large
number of potential host galaxies, no AGN are found in regions with the highest
galaxy density (excluding some cluster cores where emission from the ICM
obscures moderate luminosity AGN). AGN are also absent from the areas with
lowest galaxy density. We conclude that the prevalence of cluster AGN is linked
to their environment.Comment: 20 pages, 15 figures. MNRAS accepted. Version with full resolution
figures, including Figure 14, is available at
http://www.sc.eso.org/~rgilmour
Rebuttal to "Comment by V.M. Krasnov on 'Counterintuitive consequence of heating in strongly-driven intrinsic junctions of Bi2Sr2CaCu2O8+d Mesas' "
In our article [1], we found that with increasing dissipation there is a
clear, systematic shift and sharpening of the conductance peak along with the
disappearance of the higher-bias dip/hump features (DHF), for a stack of
intrinsic Josephson junctions (IJJs) of intercalated Bi2Sr2CaCu2O8+{\delta}
(Bi2212). Our work agrees with Zhu et al [2] on unintercalated, pristine
Bi2212, as both studies show the same systematic changes with dissipation. The
broader peaks found with reduced dissipation [1,2] are consistent with broad
peaks in the density-of-states (DOS) found among scanning tunneling
spectroscopy [3] (STS), mechanical contact tunneling [4] (MCT) and inferred
from angle (momentum) resolved photoemission spectroscopy [5] (ARPES); results
that could not be ignored. Thus, sharp peaks are extrinsic and cannot
correspond to the superconducting DOS. We suggested that the commonality of the
sharp peaks in our conductance data, which is demonstrably shown to be
heating-dominated, and the peaks of previous intrinsic tunneling spectroscopy
(ITS) data implies that these ITS reports might need reinterpretation.Comment: Rebuttal to Comment of Krasnov arXiv:1007.451
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