7,171 research outputs found
Exotic and excited-state radiative transitions in charmonium from lattice QCD
We compute, for the first time using lattice QCD methods, radiative
transition rates involving excited charmonium states, states of high spin and
exotics. Utilizing a large basis of interpolating fields we are able to project
out various excited state contributions to three-point correlators computed on
quenched anisotropic lattices. In the first lattice QCD calculation of the
exotic 1-+ eta_c1 radiative decay, we find a large partial width Gamma(eta_c1
-> J/psi gamma) ~ 100 keV. We find clear signals for electric dipole and
magnetic quadrupole transition form factors in chi_c2 -> J/psi gamma,
calculated for the first time in this framework, and study transitions
involving excited psi and chi_c1,2 states. We calculate hindered magnetic
dipole transition widths without the sensitivity to assumptions made in model
studies and find statistically significant signals, including a non-exotic
vector hybrid candidate Y_hyb? -> eta_c gamma. As well as comparison to
experimental data, we discuss in some detail the phenomenology suggested by our
results and the extent to which it mirrors that of quark potential models and
make suggestions for the interpretation of our results involving exotic quantum
numbered states
F-Seq: a feature density estimator for high-throughput sequence tags
Summary: Tag sequencing using high-throughput sequencing technologies are now regularly employed to identify specific sequence features, such as transcription factor binding sites (ChIP-seq) or regions of open chromatin (DNase-seq). To intuitively summarize and display individual sequence data as an accurate and interpretable signal, we developed F-Seq, a software package that generates a continuous tag sequence density estimation allowing identification of biologically meaningful sites whose output can be displayed directly in the UCSC Genome Browser
The Fall of the Quasar Population
We derive quantitative predictions of the optical and X-ray luminosity
functions (LF) for QSs in the redshift range . Based on BH paradigm, we
investigate how the accretion is controlled by the surrounding structures, as
these grow hierarchically. We argue that for efficient black hole
fueling is triggered by the encounters of a gas-rich host with its companions
in a group. The dispersion of the dynamical parameters in the encounters
produces a double power-law LF. Strong luminosity evolution (LE) is produced as
these encounters deplete the gas supply in the host; an additional, milder
density evolution obtains since the interactions become progressively rarer as
the groups grow richer but less dense. From the agreement with the optical and
the X-ray data, we conclude that the evolution of the bright quasars is
articulated in two ways. Earlier than the gas-rich protogalaxies grow by
merging, which also induces parallel growth of central holes accreting at
Eddington rates. In the later era of group assemblage the host encounters with
companions drive onto already existing holes further but meager accretion;
these consume the gas in the hosts, and cause supply-limited emissions which
are intermittent, go progressively sub-Eddington and peter out. Then other
fueling processes come to the foreground; we discuss the faint emissions,
especially noticeable in X-rays, which are expected when hosts in the field
cannibalize satellite galaxies with their meager gas contents.Comment: 12 pages Latex + 3 EPS figures, ApJ in press, we have corrected the
previous printing problems with the style \ca
Labour efficiency on-farm
End of project reportImprovements in milking efficiency have a greater influence than any other aspect of the dairy farmers work on overall farm labour inputs (Whipp, 1992). In order to facilitate the examination of milking process labour inputs, the milking process may be divided into the following three components: herding pre and post milking (transfer of cows to and from the milking parlour); milking (milking tasks / work routines within the parlour); and washing (washing of milking machine and yard). Meanwhile, within milking specifically, the number of cows milked per operator per hour is the best measure of both the performance of the operator and the milking installation (Clough, 1978). This is affected by the following three factors: the milking times of the cows, the number and arrangement of the milking units, and the operator’s work routine (Whipp, 1992). The addition of extra milking units will only increase milking performance if the operator has idle time during milking (Hansen, 1999)
Gravitational Lensing of the X-Ray Background by Clusters of Galaxies
Gravitational lensing by clusters of galaxies affects the cosmic X-ray
background (XRB) by altering the observed density and flux distribution of
background X-ray sources. At faint detection flux thresholds, the resolved
X-ray sources appear brighter and diluted, while the unresolved component of
the XRB appears dimmer and more anisotropic, due to lensing. The diffuse X-ray
intensity in the outer halos of clusters might be lower than the sky-averaged
XRB, after the subtraction of resolved sources. Detection of the lensing signal
with a wide-field X-ray telescope could probe the mass distribution of a
cluster out to its virialization boundary. In particular, we show that the
lensing signature imprinted on the resolved component of the XRB by the cluster
A1689, should be difficult but possible to detect out to 8' at the 2-4 sigma
level, after 10^6 seconds of observation with the forthcoming AXAF satellite.
The lensing signal is fairly insensitive to the lens redshift in the range
0.1<z<0.6. The amplitude of the lensing signal is however sensitive to the
faint end slope of the number-flux relation for unresolved X-ray sources, and
can thus help constrain models of the XRB. A search for X-ray arcs or arclets
could identify the fraction of all faint sources which originate from extended
emission of distant galaxies. The probability for a 3 sigma detection of an
arclet which is stretched by a factor of about 3 after a 10^6 seconds
observation of A1689 with AXAF, is roughly comparable to the fraction of all
background X-ray sources that have an intrinsic size of order 1''.Comment: 41 LaTeX pages, 11 postscript figures, 1 table, in AASTeX v4.0
format. To appear in ApJ, April 1, 1997, Vol. 47
Compact Nuclei in Galaxies at Moderate Redshift:II. Their Nature and Implications for the AGN Luminosity Function
This study explores the space density and properties of active galaxies to
z=0.8. We have investigated the frequency and nature of unresolved nuclei in
galaxies at moderate redshift as indicators of nuclear activity such as Active
Galactic Nuclei (AGN) or starbursts. Candidates are selected by fitting imaged
galaxies with multi-component models using maximum likelihood estimate
techniques to determine the best model fit. We select those galaxies requiring
an unresolved point-source component in the galaxy nucleus, in addition to a
disk and/or bulge component, to adequately model the galaxy light. We have
searched 70 WFPC2 images primarily from the Medium Deep Survey for galaxies
containing compact nuclei. In our survey of 1033 galaxies, the fraction
containing an unresolved nuclear component greater than 5% of the total galaxy
light is 9+/-1% corrected for incompleteness. In this second of two papers in
this series, we discuss the nature of the compact nuclei and their hosts.
We present the upper limit luminosity function (LF) for low-luminosity AGN
(LLAGN) in two redshift bins to z=0.8. Mild number density evolution is
detected for nuclei at -18 -16
and this flatness, combined with the increase in number density, is
inconsistent with pure luminosity evolution. Based on the amount of density
evolution observed for these objects, we find that almost all present-day
spiral galaxies could have hosted a LLAGN at some point in their lives. We also
comment on the likely contribution of these compact nuclei to the soft X-ray
background.Comment: 50 pages, 14 figures, to appear in ApJ, April 199
QSO clustering and the AAT 2dF redshift survey
We review previous results on the clustering and environments of QSOs. We
show that the correlation length for QSOs derived from existing surveys is
r~5/h Mpc, similar to the observed correlation length for field galaxies at the
present epoch. The galaxy environment for z<1 radio-quiet QSOs is also
consistent with field galaxies. The evolution of the QSO correlation length
with redshift is currently uncertain, largely due to the small numbers of QSOs
(~2000) in surveys suitable for clustering analysis. We report on intial
progress with the AAT 2dF QSO redshift survey, which, once completed will
comprise almost 30000 QSOs. With over 1000 QSOs already observed, it is already
the largest single homogeneous QSO survey. We discuss prospects for deriving
limits on cosmological parameters from this survey, and on the evolution of
large-scale structure in the Universe.Comment: Invited talk at RS meeting on 'Large Scale Structure in the Universe'
held at the Royal Society on 25-26 March 1998 14 pages, 11 figre
The distance to the young cluster NGC 7129 and its age
The dust cloud TGU H645 P2 and embedded in it young open cluster NGC 7129 are
investigated using the results of medium-band photometry of 159 stars in the
Vilnius seven-colour system down to V = 18.8 mag. The photometric data were
used to classify about 50 percent of the measured stars in spectral and
luminosity classes. The extinction A_V vs. distance diagram for the 20x20
arcmin area is plotted for 155 stars with two-dimensional classification from
the present and the previous catalogues. The extinction values found range
between 0.6 and 3.4 mag. However, some red giants, located in the direction of
the dense parts of the cloud, exhibit the infrared extinction equivalent up to
A_V = 13 mag. The distance to the cloud (and the cluster) is found to be 1.15
kpc (the true distance modulus 10.30 mag). For determining the age of NGC 7129,
a luminosity vs. temperature diagram for six cluster members of spectral
classes B3 to A1 was compared with the Pisa pre-main-sequence evolution tracks
and the Palla birthlines. The cluster can be as old as about 3 Myr, but star
forming continues till now as witnessed by the presence in the cloud of many
younger pre-main-sequence objects identified with photometry from 2MASS,
Spitzer and WISE infrared surveys.Comment: 8 pages, 6 fugures, full Table 1 online. Accepted for publication in
MNRAS on 2013 November 3
The anti-emetic potential of the 5-hydroxytryptamine3 receptor antagonist BRL 43694.
In ferrets, the selective 5-hydroxytryptamine (5-HT) 5-HT3 receptor antagonist BRL 43694 given as a single injection (0.05-0.5 mg kg-1 i.v.) before cisplatin, or by divided dose (2 x 0.005-2 x 0.5 mg kg-1 i.v.) before and after cisplatin dramatically reduced or abolished the severe cisplatin-induced vomiting. BRL 43694 also substantially reduced the vomiting induced by cyclophosphamide:doxorubicin, and prevented the trimelamol-induced emesis. The severe emesis caused by whole body exposure to X-irradiation was prevented by intravenous or oral BRL 43694. A single i.v. dose of BRL 43694 given during an emetic episode or within the peak emetic period, abolished the vomiting induced by the cytotoxic drugs and by X-irradiation, usually within 30 s. Where the induction of emesis was prevented or subsequently abolished by BRL 43694, the associated behaviour (subjectively assessed as nausea) was also absent or greatly attenuated. BRL 43694 (0.1 mg kg-1 i.v.) did not affect the emesis evoked in dogs by the dopamine agonist apomorphine. The potent anti-emetic activity of BRL 43694 is discussed in terms of potential clinical use, and of the fundamental role that 5-HT3 receptors may play in the mechanisms of nausea and vomiting
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