73 research outputs found
New bryophyte taxon records for tropical countries 1
This is the first in a series of papers listing new records, which will be published whenever sufficient new records have been found. The taxa are arranged by countries for an easier evaluation, e.g. updates of checklists. The initials of the contributor for each record is shown in square brackets after the record, and these initials are interpreted at the end of the paper
British Bryological Society expedition to Mulanje Mountain, Malawi : 13., new and other unpublished records
Further results are provided of the 1991 British Bryological Society Expedition to Mulanje Mt., Malawi including 168 taxa of bryophyte, comprising 72 taxa of liverwort (38 new to Malawi) and 96 taxa of mosses (45 new to Malawi)
The Santa Fe Light Cone Simulation Project: I. Confusion and the WHIM in Upcoming Sunyaev-Zel'dovich Effect Surveys
We present the first results from a new generation of simulated large sky
coverage (~100 square degrees) Sunyaev-Zeldovich effect (SZE) cluster surveys
using the cosmological adaptive mesh refinement N-body/hydro code Enzo. We have
simulated a very large (512^3h^{-3}Mpc^3) volume with unprecedented dynamic
range. We have generated simulated light cones to match the resolution and
sensitivity of current and future SZE instruments. Unlike many previous studies
of this type, our simulation includes unbound gas, where an appreciable
fraction of the baryons in the universe reside.
We have found that cluster line-of-sight overlap may be a significant issue
in upcoming single-dish SZE surveys. Smaller beam surveys (~1 arcmin) have more
than one massive cluster within a beam diameter 5-10% of the time, and a larger
beam experiment like Planck has multiple clusters per beam 60% of the time. We
explore the contribution of unresolved halos and unbound gas to the SZE
signature at the maximum decrement. We find that there is a contribution from
gas outside clusters of ~16% per object on average for upcoming surveys. This
adds both bias and scatter to the deduced value of the integrated SZE, adding
difficulty in accurately calibrating a cluster Y-M relationship.
Finally, we find that in images where objects with M > 5x10^{13} M_{\odot}
have had their SZE signatures removed, roughly a third of the total SZE flux
still remains. This gas exists at least partially in the Warm Hot Intergalactic
Medium (WHIM), and will possibly be detectable with the upcoming generation of
SZE surveys.Comment: 14 pages, 13 figures, version accepted to ApJ. Major revisions mad
Bryophytes of Uganda : 6., new and additional records, 3.
12 hepatics and 32 mosses are reported new to Uganda, 1 moss being also new to Africa, and 1 liverwort new to mainland Africa. Ectropothecium plumigerum (Broth.) HedenĂ€s is a new combination (basionym: Isopterygium plumigerum Broth.) with a new synonym Taxicaulis plumirameus MĂŒll.Hal. nom. nud., and Taxiphyllum maniae (Renauld & Paris) M. Fleisch. is a new synonym of Taxiphyllum taxirameum (Mitt.) M.Fleisch. Three mosses are removed from the Uganda list
Cosmological Shocks in Adaptive Mesh Refinement Simulations and the Acceleration of Cosmic Rays
We present new results characterizing cosmological shocks within adaptive
mesh refinement N-Body/hydrodynamic simulations that are used to predict
non-thermal components of large-scale structure. This represents the first
study of shocks using adaptive mesh refinement. We propose a modified algorithm
for finding shocks from those used on unigrid simulations that reduces the
shock frequency of low Mach number shocks by a factor of ~3. We then apply our
new technique to a large, (512 Mpc/h)^3, cosmological volume and study the
shock Mach number (M) distribution as a function of pre-shock temperature,
density, and redshift. Because of the large volume of the simulation, we have
superb statistics that results from having thousands of galaxy clusters. We
find that the Mach number evolution can be interpreted as a method to visualize
large-scale structure formation. Shocks with Mach<5 typically trace mergers and
complex flows, while 520 generally follow accretion onto
filaments and galaxy clusters, respectively. By applying results from nonlinear
diffusive shock acceleration models using the first-order Fermi process, we
calculate the amount of kinetic energy that is converted into cosmic ray
protons. The acceleration of cosmic ray protons is large enough that in order
to use galaxy clusters as cosmological probes, the dynamic response of the gas
to the cosmic rays must be included in future numerical simulations.Comment: 15 pages, 14 figures, Accepted to ApJ, minor changes mad
Comparing AMR and SPH Cosmological Simulations: I. Dark Matter & Adiabatic Simulations
We compare two cosmological hydrodynamic simulation codes in the context of
hierarchical galaxy formation: The SPH code GADGET, and the Eulerian AMR code
ENZO. Both codes represent dark matter with the N-body method, but use
different gravity solvers and fundamentally different approaches to
hydrodynamics. We compare the GADGET `entropy conserving' SPH formulation with
two ENZO methods: The piecewise parabolic method (PPM), and the artificial
viscosity-based scheme used in the ZEUS code. In this paper we focus on a
comparison of cosmological simulations that follow either only dark matter, or
also adiabatic baryonic gas. The dark matter-only runs agree generally quite
well, provided ENZO is run with a comparatively fine root grid and a low
overdensity threshold for mesh refinement, otherwise the abundance of low-mass
halos is suppressed. This is due to the hierarchical particle-mesh method used
to compute gravitational forces in ENZO, which tends to deliver lower force
resolution than the tree algorithm of GADGET. At comparable force resolution,
we find that the latter offers substantially better performance and lower
memory consumption than the present gravity solver in ENZO. In simulations that
include adiabatic gas dynamics, we find general agreement in the distribution
functions of temperature, entropy, and density for gas of moderate to high
overdensity, as found inside dark matter halos. However, there are some
significant differences at lower overdensities. We argue that these
discrepancies are presumably owing to differences in the shock-capturing
abilities of the different methods. In particular, ZEUS hydro leads to some
unphysical heating at early times in preshock regions. Overall, the GADGET
hydro results are bracketed by those for ENZO/ZEUS and ENZO/PPM. (abridged)Comment: 45 pages, 17 figures. ApJ, in press. This paper has been
significantly revised after referee comments and several sections have been
adde
Implicit and explicit COVIDâ19âvaccine harmfulness/helpfulness associations predict vaccine beliefs, intentions, and behaviors
We investigated the role of implicit and explicit associations between harm and COVID-19 vaccines using a large sample (N = 4668) of online volunteers. The participants completed a brief implicit association test and explicit measures to evaluate the extent to which they associated COVID-19 vaccines with concepts of harmfulness or helpfulness. We examined the relationship between these harmfulness/helpfulness COVID-19 vaccine associations and vaccination status, intentions, beliefs, and behavior. We found that stronger implicit and explicit associations that COVID-19 vaccines are helpful relate to vaccination status and beliefs about the COVID-19 vaccine. That is, stronger pro-helpful COVID-19 vaccine associations, both implicitly and explicitly, related to greater intentions to be vaccinated, more positive beliefs about the vaccine, and greater vaccine uptake
The Role of Uncertainty, Worry, and Control in Well-Being: Evidence From the COVID-19 Outbreak and Pandemic in U.S. and China
Uncertainty about the future often leads to worries about what the future will bring, which can have negative consequences for health and well-being. However, if worry can act as a motivator to promote efforts to prevent undesirable future outcomes, those negative consequences of worry may be mitigated. In this article, we apply a novel model of uncertainty, worry, and perceived control to predict psychological and physical well-being among four samples collected in China (Study 1; during the early COVID-19 outbreak in China) and the United States (Studies 2â4, during 4 weeks in May 2020, 4 weeks in November 2020, and crosssectionally between April and November 2020). Grounded in the feeling-is-for-doing approach to emotions, we hypothesized (and found) that uncertainty about oneâs COVID-19 risk would predict greater worry about the virus and oneâs risk of contracting it, and that greater worry would in turn predict poorer well-being. We also hypothesized, and found somewhat mixed evidence, that perceptions of control over 1âs COVID-19 risk moderated the relationship between worry and well-being such that worry was related to diminished well-being when people felt they lacked control over their risk for contracting the virus. This study is one of the first to demonstrate an indirect path from uncertainty to well-being via worry and to demonstrate the role of control in moderating whether uncertainty and worry manifest in poor well-being
Signatures of minor mergers in the Milky Way disc I: The SEGUE stellar sample
It is now known that minor mergers are capable of creating structure in the
phase-space distribution of their host galaxy's disc. In order to search for
such imprints in the Milky Way, we analyse the SEGUE F/G-dwarf and the Schuster
et al. (2006) stellar samples. We find similar features in these two completely
independent stellar samples, consistent with the predictions of a Milky Way
minor-merger event. We next apply the same analyses to high-resolution,
idealised N-body simulations of the interaction between the Sagittarius dwarf
galaxy and the Milky Way. The energy distributions of stellar particle samples
in small spatial regions in the host disc reveal strong variations of structure
with position. We find good matches to the observations for models with a mass
of Sagittarius' dark matter halo progenitor M.
Thus, we show that this kind of analysis could be used to provide
unprecedentedly tight constraints on Sagittarius' orbital parameters, as well
as place a lower limit on its mass.Comment: 14 pages, 9 figures, 2 tables. Revised to reflect accepted versio
Comment on Spracklandus Hoser, 2009 (Reptilia, Serpentes, ELAPIDAE): request for confirmation of the availability of the generic name and for the nomenclatural validation of the journal in which it was published (Case 3601; see BZN 70: 234â237; 71: 30â38, 133â135, 181â182, 252â253)
- âŠ