12,735 research outputs found
Genetic Differentiation Among Three Species of \u3ci\u3eParadosa\u3c/i\u3e (Arachnida: Lycosidae)
Allozymic variation in nine protein producing loci was examined in three species of Pardosa using starch gel electrophoresis. Allozyme frequencies showed a high degree of geographic uniformity among conspecific populations. Estimated heterozygosities for the three species ranged from 0.05 to 0.15. Rogers\u27 coefficients of genetic similarity based on allozyme frequencies averaged over conspecific populations ranged from 0.16 to 0.37 fo rthe three species
Further implications of the Bessis-Moussa-Villani conjecture
We find further implications of the BMV conjecture, which states that for
hermitian matrices A and B, the function Tr exp(A - t B) is the Laplace
transform of a positive measure.Comment: LaTeX, 8 page
The long gamma-ray burst rate and the correlation with host galaxy properties
To answer questions on the start and duration of the epoch of reionisation,
periods of galaxy mergers and properties of other cosmological encounters, the
cosmic star formation history (CSFH), is of fundamental importance. Using the
association of long gamma-ray bursts (LGRBs) with the death of massive stars
and their ultra-luminous nature, the CSFH can be probed to higher redshifts
than current conventional methods. Unfortunately, no consensus has been reached
on the manner in which the LGRB rate (LGRBR) traces the CSFH, leaving many of
the questions mentioned mostly unexplored by this method. Observations by the
GRB NIR detector (GROND) over the past 4 years have, for the first time,
acquired highly complete LGRB samples. Driven by these completeness levels and
new evidence of LGRBs also occurring in more massive and metal rich galaxies
than previously thought, the possible biases of the LGRBR-CSFH connection are
investigated over a large range of galaxy properties. The CSFH is modelled
using empirical fits to the galaxy mass function and galaxy star formation
rates. Biasing the CSFH by metallicity cuts, mass range boundaries, and other
unknown redshift dependencies, a LGRBR is generated and compared to the highly
complete GROND sample. It is found that there is no strong preference for a
metallicity cut or fixed galaxy mass boundaries and that there are no unknown
redshift effects, in contrast to previous work which suggest values of
Z/Z_sun~0.1-0.3. From the best-fit models, we predict that ~1.2% of the LGRB
burst sample exists above z=6. The linear relationship between the LGRBR and
the CSFH suggested by our results implies that redshift biases present in
previous LGRB samples significantly affect the inferred dependencies of LGRBs
on their host galaxy properties. Such biases can lead to, e.g., an
interpretation of metallicity limitations and evolving LGRB luminosity
functions.Comment: 15 pages, 14 figures, 7 tables, accepted for publication in Astronomy
& Astrophysic
Alpha Backgrounds for HPGe Detectors in Neutrinoless Double-Beta Decay Experiments
The Majorana Experiment will use arrays of enriched HPGe detectors to search
for the neutrinoless double-beta decay of 76Ge. Such a decay, if found, would
show lepton-number violation and confirm the Majorana nature of the neutrino.
Searches for such rare events are hindered by obscuring backgrounds which must
be understood and mitigated as much as possible. A potentially important
background contribution to this and other double-beta decay experiments could
come from decays of alpha-emitting isotopes in the 232Th and 238U decay chains
on or near the surfaces of the detectors. An alpha particle emitted external to
an HPGe crystal can lose energy before entering the active region of the
detector, either in some external-bulk material or within the dead region of
the crystal. The measured energy of the event will only correspond to a partial
amount of the total kinetic energy of the alpha and might obscure the signal
from neutrinoless double-beta decay. A test stand was built and measurements
were performed to quantitatively assess this background. We present results
from these measurements and compare them to simulations using Geant4. These
results are then used to measure the alpha backgrounds in an underground
detector in situ. We also make estimates of surface contamination tolerances
for double-beta decay experiments using solid-state detectors.Comment: 10 pages, 11 figures, submitted to NIM
Mitigating social and economic sources of trauma:the need for Universal Basic Income during the Coronavirus Pandemic
The COVID-19 Pandemic is projected to cause an economic shock larger than the Global Financial Crisis of 2007/2008 and a recession as great as anything seen since the Great Depression in 1930s. The social and economic consequences of lockdowns and social distancing measures, such as unemployment, broken relationships and homelessness create potential for inter-generational trauma extending decades into the future. In this article, we argue that, in the absence of a vaccine, governments need to introduce Universal Basic Income as a means of mitigating this trauma
Book Reviews
Several reviews from the African Book Publishing Review (ABPR) are included in this article. Also included are reviews of South Africa and Africa: Within or Apart? and Global Restructuring and Peripheral States: The Carrot and the Stick in Mauritani
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