403 research outputs found
Estimation of badger abundance using faecal DNA typing
1.Wildlife management and conservation programmes often require accurate information
on population density, but this can be difficult to obtain, particularly when the species in question is nocturnal or cryptic. Badger populations in Britain are of intense management interest because they are a wildlife reservoir host of bovine tuberculosis (TB). Attempts to manage this infection in badgers, whether by population control or vaccination, require reliable methods of estimating population size. In addition, such estimates are also required to support research into badger ecology and TB epidemiology. Currently, the most accurate estimates of local badger population size are
obtained from labour-intensive and time-consuming mark–recapture studies. 2. In recent years, DNA has been successfully extracted from the faeces of certain mammals,
and used to generate a genetic profile of the defecating individual. Here we report on an application of this technology to estimate badger abundance.3.Faecal samples were collected on 10 consecutive days from every freshly deposited dropping at latrine sites close to occupied setts in three badger social groups. Badger
DNA was extracted from 89% of samples, and 20 different individuals were reliably identified. The genotypes derived from the faecal samples were compared with those
obtained from blood or samples from badgers live trapped at the same setts.4.The faecal genotypes from badgers with known trap histories revealed that latrines were used equally by males and females, and by badgers ranging in age from cubs(< 1 year old) to 9 years old. Individual badgers used the latrines on between one and six different nights. Rarefaction analysis produced abundance estimates that closely matched those obtained from live trapping.
5.Synthesis and applications. Systematic sampling and genetic typing of fresh faeces from badger latrines can provide data that can be used to estimate abundance accurately.This approach requires considerably less human resources than repeated live trapping
and mark–recapture. The technique may be valuable for future badger research and management in relation to bovine TB, where accurate estimates of abundance at a local
scale are required
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Laminated Object Manufacturing of Si3N4 With Enhanced Properties
The potential to fabricate near net-shape ceramic components of intricate shape is attractive
and offers considerable savings in cost and time. The laminated architecture inherent in many
Rapid Prototyping techniques can be utilized to enhance material properties by providing weak
interfaces at regular intervals, oriented microstructures, and functionally graded compositions. By
design and control of these variables it is possible to enhance the strength, toughness and
performance of components fabricated from structural ceramics. A range of oriented
microstructural features have been investigated in Laminated Object Manufacturing of Si3N4
materials. Changes in the mechanical properties can be related to specific architectures and
microstructural developments which took place during sintering.Mechanical Engineerin
Geometric and thermodynamic properties in Gauss-Bonnet gravity
In this paper, the generalized second law (GSL) of thermodynamics and entropy
is revisited in the context of cosmological models in Gauss-Bonnet gravity with
the boundary of the universe is assumed to be enclosed by the dynamical
apparent horizon. The model is best fitted with the observational data for
distance modulus. The best fitted geometric and thermodynamic parameters such
as equation of state parameter, deceleration parameter and entropy are derived.
To link between thermodynamic and geometric parameters, the "entropy rate of
change multiplied by the temperature" as a model independent thermodynamic
state parameter is also derived. The results show that the model is in good
agreement with the observational analysis.Comment: 13 pages, 13 figures, to be published in Astrophysics and Space Sc
Cosmological parameters from SDSS and WMAP
We measure cosmological parameters using the three-dimensional power spectrum
P(k) from over 200,000 galaxies in the Sloan Digital Sky Survey (SDSS) in
combination with WMAP and other data. Our results are consistent with a
``vanilla'' flat adiabatic Lambda-CDM model without tilt (n=1), running tilt,
tensor modes or massive neutrinos. Adding SDSS information more than halves the
WMAP-only error bars on some parameters, tightening 1 sigma constraints on the
Hubble parameter from h~0.74+0.18-0.07 to h~0.70+0.04-0.03, on the matter
density from Omega_m~0.25+/-0.10 to Omega_m~0.30+/-0.04 (1 sigma) and on
neutrino masses from <11 eV to <0.6 eV (95%). SDSS helps even more when
dropping prior assumptions about curvature, neutrinos, tensor modes and the
equation of state. Our results are in substantial agreement with the joint
analysis of WMAP and the 2dF Galaxy Redshift Survey, which is an impressive
consistency check with independent redshift survey data and analysis
techniques. In this paper, we place particular emphasis on clarifying the
physical origin of the constraints, i.e., what we do and do not know when using
different data sets and prior assumptions. For instance, dropping the
assumption that space is perfectly flat, the WMAP-only constraint on the
measured age of the Universe tightens from t0~16.3+2.3-1.8 Gyr to
t0~14.1+1.0-0.9 Gyr by adding SDSS and SN Ia data. Including tensors, running
tilt, neutrino mass and equation of state in the list of free parameters, many
constraints are still quite weak, but future cosmological measurements from
SDSS and other sources should allow these to be substantially tightened.Comment: Minor revisions to match accepted PRD version. SDSS data and ppt
figures available at http://www.hep.upenn.edu/~max/sdsspars.htm
Cosmological constraints from galaxy clustering
In this manuscript I review the mathematics and physics that underpins recent
work using the clustering of galaxies to derive cosmological model constraints.
I start by describing the basic concepts, and gradually move on to some of the
complexities involved in analysing galaxy redshift surveys, focusing on the 2dF
Galaxy Redshift Survey (2dFGRS) and the Sloan Digital Sky survey (SDSS).
Difficulties within such an analysis, particularly dealing with redshift space
distortions and galaxy bias are highlighted. I then describe current
observations of the CMB fluctuation power spectrum, and consider the importance
of measurements of the clustering of galaxies in light of recent experiments.
Finally, I provide an example joint analysis of the latest CMB and large-scale
structure data, leading to a set of parameter constraints.Comment: 30 pages, 13 figures. Lecture given at Third Aegean Summer School,
The invisible universe: Dark matter and Dark energ
Proximity effect at superconducting Sn-Bi2Se3 interface
We have investigated the conductance spectra of Sn-Bi2Se3 interface junctions
down to 250 mK and in different magnetic fields. A number of conductance
anomalies were observed below the superconducting transition temperature of Sn,
including a small gap different from that of Sn, and a zero-bias conductance
peak growing up at lower temperatures. We discussed the possible origins of the
smaller gap and the zero-bias conductance peak. These phenomena support that a
proximity-effect-induced chiral superconducting phase is formed at the
interface between the superconducting Sn and the strong spin-orbit coupling
material Bi2Se3.Comment: 7 pages, 8 figure
Centrality Dependence of the High p_T Charged Hadron Suppression in Au+Au collisions at sqrt(s_NN) = 130 GeV
PHENIX has measured the centrality dependence of charged hadron p_T spectra
from central Au+Au collisions at sqrt(s_NN)=130 GeV. The truncated mean p_T
decreases with centrality for p_T > 2 GeV/c, indicating an apparent reduction
of the contribution from hard scattering to high p_T hadron production. For
central collisions the yield at high p_T is shown to be suppressed compared to
binary nucleon-nucleon collision scaling of p+p data. This suppression is
monotonically increasing with centrality, but most of the change occurs below
30% centrality, i.e. for collisions with less than about 140 participating
nucleons. The observed p_T and centrality dependence is consistent with the
particle production predicted by models including hard scattering and
subsequent energy loss of the scattered partons in the dense matter created in
the collisions.Comment: 7 pages text, LaTeX, 6 figures, 2 tables, 307 authors, resubmitted to
Phys. Lett. B. Revised to address referee concerns. Plain text data tables
for the points plotted in figures for this and previous PHENIX publications
are publicly available at
http://www.phenix.bnl.gov/phenix/WWW/run/phenix/papers.htm
The PHENIX Experiment at RHIC
The physics emphases of the PHENIX collaboration and the design and current
status of the PHENIX detector are discussed. The plan of the collaboration for
making the most effective use of the available luminosity in the first years of
RHIC operation is also presented.Comment: 5 pages, 1 figure. Further details of the PHENIX physics program
available at http://www.rhic.bnl.gov/phenix
Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration
Extensive experimental data from high-energy nucleus-nucleus collisions were
recorded using the PHENIX detector at the Relativistic Heavy Ion Collider
(RHIC). The comprehensive set of measurements from the first three years of
RHIC operation includes charged particle multiplicities, transverse energy,
yield ratios and spectra of identified hadrons in a wide range of transverse
momenta (p_T), elliptic flow, two-particle correlations, non-statistical
fluctuations, and suppression of particle production at high p_T. The results
are examined with an emphasis on implications for the formation of a new state
of dense matter. We find that the state of matter created at RHIC cannot be
described in terms of ordinary color neutral hadrons.Comment: 510 authors, 127 pages text, 56 figures, 1 tables, LaTeX. Submitted
to Nuclear Physics A as a regular article; v3 has minor changes in response
to referee comments. Plain text data tables for the points plotted in figures
for this and previous PHENIX publications are (or will be) publicly available
at http://www.phenix.bnl.gov/papers.htm
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