3,121 research outputs found
Water vole (Arvicola amphibius) abundance in grassland habitats of Glasgow
Water vole (Arvicola amphibius) populations have
undergone a serious decline throughout the UK, and
yet a stronghold of these small mammals is found in
the greater Easterhouse area of Glasgow. The water
voles in this location are mostly fossorial, living a
largely subterranean existence in grasslands, rather
than the more typical semi-aquatic lifestyle in
riparian habitats. In this study, we carried out
capture-mark-recapture surveys on water voles at
two sites: Cranhill Park and Tillycairn Drive. We
made a total of 62 captures including retraps, and the
resulting population estimates were 78 individuals
(95% confidence interval 41-197) for Cranhill Park
and 42 individuals (20-141) for Tillycairn Drive.
From these figures we estimated a population
density of water voles, which appeared to be higher
than other reports from the UK. Despite the
difficulties of sampling in urban environments that
resulted in relatively low capture rates, our data
suggest that the greater Easterhouse area of Glasgow
holds water voles at relatively high population
densities. These results will inform future
conservation in the City of Glasgow and surrounding
areas, as well as raise awareness of important water
vole populations in urban environments
Can FCNC transition be seen in decays?
The decays present in principle the opportunity to observe the
short distance FCNC transition , which is sensitive to the
physics beyond the Standard Model. We analyze the decays
within the Standard Model, where in addition to the short distance dynamics
also the long distance dynamics is present. The short distance contribution due
to transition, which is present only in the Cabibbo suppressed
decays, is found to be three orders of magnitude smaller than the long distance
contribution. The branching ratios well above for Cabibbo suppressed
decays could signal new physics. The most frequent decays are the Cabibbo
allowed decays and ,
which are expected at the branching ratios of and , respectively. These rates are not much lower than the present
experimental upper limit.Comment: 3 pages, latex, 3 figures, Talk given by S. Prelovsek at the
Hyperons, Charm and Beauty Hadrons, Genova, Italy, 30 June -3 July 1998, to
appear as proceedings in Nucl. Phys.
Lateral Distribution for Aligned Events in Muon Groups Deep Underground
The paper concerns the so-called aligned events observed in cosmic rays. The
phenomenon of the alignment of the most energetic subcores of gamma-ray--hadron
() families (particles of the highest energies in the central EAS
core) was firstly found in the "Pamir" emulsion chamber experiment and related
to a coplanar particle production at eV. Here a separation
distribution (distances between pairs of muons) for aligned events has been
analyzed throughout muon groups measured by Baksan Underground Scintillation
Telescope (BUST) for threshold energies TeV during a period of
7.7 years. Only muon groups of multiplicity with inclined
trajectories for an interval of zenith angles were
selected for the analysis. The analysis has revealed that the distribution
complies with the exponential law. Meanwhile the distributions become steeper
with the increase of threshold energy. There has been no difference between the
lateral distribution of all the groups and the distribution of the aligned
groups.Comment: 4 pages, 3 figures. Prepared for the ISVHECRI'2006, Weihai, Chin
Intolerant baboons avoid observer proximity, creating biased inter-individual association patterns
Social network analysis is an increasingly popular tool for behavioural ecologists exploring the social organisation of animal populations. Such analyses require data on inter-individual association patterns, which in wild populations are often collected using direct observations of habituated animals. This assumes observers have no influence on animal behaviour; however, our previous work showed that individuals in a habituated group of chacma baboons (Papio ursinus griseipes) displayed consistent and individually distinct responses to observer approaches. We explored the implications of our previous findings by measuring the inter-individual association patterns of the same group of chacma baboons at different observer distances. We found a strong positive association between individual tolerance levels (towards observers) and how often an animal appeared as a neighbour to focal animals when observers were nearer, and a neutral relationship between the same variables when the observer was further away. Additionally, association matrices constructed from different observation distances were not comparable within any proximity buffer, and neither were the individual network metrics generated from these matrices. This appears to be the first empirical evidence that observer presence and behaviour can influence the association patterns of habituated animals and thus have potentially significant impacts on measured social networks
An inverse method for estimating thickness and volume with time of a thin CO2-filled layer at the Sleipner Field, North Sea
Migration of CO
2
through storage reservoirs can be monitored using time lapse seismic
reflection surveys. At the Sleipner Field, injected CO
2
is distributed throughout nine layers within the
reservoir. These layers are too thin to be seismically resolvable by direct measurement of the separation
between reflections from the top and bottom of each layer. Here we develop and apply an inverse method
for measuring thick ness changes of the shallowest layer. Our approach combines differences in traveltime
down to a specific reflection together with amplitude measurements to determine layer thicknesses from
time lapse surveys. A series of synthetic forward models were used to test the robustness of our inverse
approach and to quantify uncertainties. In the absence of ambient noise, this approach can unambiguously
resolve layer thickness. If a realistic ambient noise distribution is included, layer thicknesses of 1–6 m are
accurately retrieved with an uncertainty of ±0.5 m. We used this approach to generate a thickness map
of the shallowest layer. The fidelity of this result was tested using measurements of layer thickness
determined from the 2010 broadband seismic survey. The calculated volume of CO
2
within the shallowest
layer increases at a rate that is quadratic in time, despite an approximately constant injection rate into the
base of the reser voir. This result is consistent with a diminished growth rate of the areal extent of underlying
layers. Finally, the relationship between caprock topography and layer thickness is explored and potential
migration pathways that charge this layer are identified
Confinement of matroid representations to subsets of partial fields
Let M be a matroid representable over a (partial) field P and B a matrix
representable over a sub-partial field P' of P. We say that B confines M to P'
if, whenever a P-representation matrix A of M has a submatrix B, A is a scaled
P'-matrix. We show that, under some conditions on the partial fields, on M, and
on B, verifying whether B confines M to P' amounts to a finite check. A
corollary of this result is Whittle's Stabilizer Theorem.
A combination of the Confinement Theorem and the Lift Theorem from
arXiv:0804.3263 leads to a short proof of Whittle's characterization of the
matroids representable over GF(3) and other fields.
We also use a combination of the Confinement Theorem and the Lift Theorem to
prove a characterization, in terms of representability over partial fields, of
the 3-connected matroids that have k inequivalent representations over GF(5),
for k = 1, ..., 6.
Additionally we give, for a fixed matroid M, an algebraic construction of a
partial field P_M and a representation A over P_M such that every
representation of M over a partial field P is equal to f(A) for some
homomorphism f:P_M->P. Using the Confinement Theorem we prove an algebraic
analog of the theory of free expansions by Geelen et al.Comment: 45 page
Supersoft X-Ray Sources in M31
The nearby Andromeda galaxy (M31) has been observed with the ROSAT PSPC in a
mosaic of 6 pointings with 25 ksec each. In the paper describing the results on
the total sample of detected sources, Supper et al. (1996) also report the
positions for 15 supersoft X-ray sources and the blackbody fit results for the
brightest of these sources. We report here in more detail on the X-ray spectral
characteristics of all these 15 supersoft X-ray sources. Optical multi-colour
photometric data obtained in 1990 at the Michigan- Dartmouth-MIT Observatory at
Kitt Peak were used originally in the selection process of the supersoft
sources, and are the basis for the finding charts given here for most selected
X-ray sources.Comment: 8 pages postscript incl. figures, Proc. of Workshop on Supersoft
X-Ray Sources, to appear in Lecture Notes in Physics vol. 472 (1996
Ground state of the random-bond spin-1 Heisenberg chain
Stochastic series expansion quantum Monte Carlo is used to study the ground
state of the antiferromagnetic spin-1 Heisenberg chain with bond disorder.
Typical spin- and string-correlations functions behave in accordance with
real-space renormalization group predictions for the random-singlet phase. The
average string-correlation function decays algebraically with an exponent of
-0.378(6), in very good agreement with the prediction of , while the average spin-correlation function is found to decay with an
exponent of about -1, quite different from the expected value of -2. By
implementing the concept of directed loops for the spin-1 chain we show that
autocorrelation times can be reduced by up to two orders of magnitude.Comment: 9 pages, 10 figure
Seismic data reveal eastern Black Sea Basin structure
Rifted continental margins are formed by progressive extension of the lithosphere. The development of these margins plays an integral role in the plate tectonic cycle, and an understanding of the extensional process underpins much hydrocarbon exploration. A key issue is whether the lithosphere extends uniformly, or whether extension varies\ud
with depth. Crustal extension may be determined using seismic techniques. Lithospheric extension may be inferred from the waterloaded subsidence history, determined from\ud
the pattern of sedimentation during and after rifting. Unfortunately, however, many rifted margins are sediment-starved, so the subsidence history is poorly known.\ud
To test whether extension varies between the crust and the mantle, a major seismic experiment was conducted in February–March 2005 in the eastern Black Sea Basin (Figure 1), a deep basin where the subsidence history is recorded\ud
by a thick, post-rift sedimentary sequence. The seismic data from the experiment indicate the presence of a thick, low-velocity zone, possibly representing overpressured sediments. They also indicate that the basement and\ud
Moho in the center of the basin are both several kilometers shallower than previously inferred. These initial observations may have considerable impact on thermal models of the petroleum system in the basin. Understanding\ud
the thermal history of potential source rocks is key to reducing hydrocarbon exploration risk. The experiment, which involved collaboration between university groups in the United Kingdom, Ireland, and Turkey, and BP and\ud
Turkish Petroleum (TPAO), formed part of a larger project that also is using deep seismic reflection and other geophysical data held by the industry partners to determine the subsidence history and hence the strain evolution of\ud
the basin
Representing some non-representable matroids
We extend the notion of representation of a matroid to algebraic structures
that we call skew partial fields. Our definition of such representations
extends Tutte's definition, using chain groups. We show how such
representations behave under duality and minors, we extend Tutte's
representability criterion to this new class, and we study the generator
matrices of the chain groups. An example shows that the class of matroids
representable over a skew partial field properly contains the class of matroids
representable over a skew field.
Next, we show that every multilinear representation of a matroid can be seen
as a representation over a skew partial field.
Finally we study a class of matroids called quaternionic unimodular. We prove
a generalization of the Matrix Tree theorem for this class.Comment: 29 pages, 2 figure
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