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Evolutionary bi-stability in pathogen transmission mode
Many pathogens transmit to new hosts by both infection (horizontal transmission) and transfer to the
infected host's offspring (vertical transmission). These two transmission modes require speci®c adap-
tations of the pathogen that can be mutually exclusive, resulting in a trade-off between horizontal and
vertical transmission. We show that in mathematical models such trade-offs can lead to the simultaneous
existence of two evolutionary stable states (evolutionary bi-stability) of allocation of resources to the two
modes of transmission. We also show that jumping between evolutionary stable states can be induced by
gradual environmental changes. Using quantitative PCR-based estimates of abundance in seed and vege-
tative parts, we show that the pathogen of wheat, Phaeosphaeria nodorum, has jumped between two
distinct states of transmission mode twice in the past 160 years, which, based on published evidence,
we interpret as adaptation to environmental change. The ®nding of evolutionary bi-stability has impli-
cations for human, animal and other plant diseases. An ill-judged change in a disease control
programme could cause the pathogen to evolve a new, and possibly more damaging, combination of
transmission modes. Similarly, environmental changes can shift the balance between transmission
modes, with adverse effects on human, animal and plant health
Mechanisms of MR/N024524/1Scarless Repair at Time of Menstruation: Insights From Mouse Models
The human endometrium is a remarkable tissue which may experience up to 400 cycles of hormone-driven proliferation, differentiation and breakdown during a woman's reproductive lifetime. During menstruation, when the luminal portion of tissue breaks down, it resembles a bloody wound with piecemeal shedding, exposure of underlying stroma and a strong inflammatory reaction. In the absence of pathology within a few days the integrity of the tissue is restored without formation of a scar and the endometrium is able to respond appropriately to subsequent endocrine signals in preparation for establishment of pregnancy if fertilization occurs. Understanding mechanisms regulating scarless repair of the endometrium is important both for design of therapies which can treat conditions where this is aberrant (heavy menstrual bleeding, fibroids, endometriosis, Asherman's syndrome) as well as to provide new information that might allow us to reduce fibrosis and scar formation in other tissues. Menstruation only occurs naturally in species that exhibit spontaneous stromal cell decidualization during the fertile cycle such as primates (including women) and the Spiny mouse. To take advantage of genetic models and detailed time course analysis, mouse models of endometrial shedding/repair involving hormonal manipulation, artificial induction of decidualization and hormone withdrawal have been developed and refined. These models are useful in modeling dynamic changes across the time course of repair and have recapitulated key features of endometrial repair in women including local hypoxia and immune cell recruitment. In this review we will consider the evidence that scarless repair of endometrial tissue involves changes in stromal cell function including mesenchyme to epithelial transition, epithelial cell proliferation and multiple populations of immune cells. Processes contributing to endometrial fibrosis (Asherman's syndrome) as well as scarless repair of other tissues including skin and oral mucosa are compared to that of menstrual repair
High-efficiency WSi superconducting nanowire single-photon detectors for quantum state engineering in the near infrared
We report on high-efficiency superconducting nanowire single-photon detectors
based on amorphous WSi and optimized at 1064 nm. At an operating temperature of
1.8 K, we demonstrated a 93% system detection efficiency at this wavelength
with a dark noise of a few counts per second. Combined with cavity-enhanced
spontaneous parametric down-conversion, this fiber-coupled detector enabled us
to generate narrowband single photons with a heralding efficiency greater than
90% and a high spectral brightness of
photons/(smWMHz). Beyond single-photon generation at large rate,
such high-efficiency detectors open the path to efficient multiple-photon
heralding and complex quantum state engineering
Events leading up to the June 2015 outburst of V404 Cyg
On 2015 June 15 the burst alert telescope (BAT) on board {\em Swift} detected
an X-ray outburst from the black hole transient V404 Cyg. We monitored V404 Cyg
for the last 10 years with the 2-m Faulkes Telescope North in three optical
bands (V, R, and i). We found that, one week prior to this outburst, the
optical flux was 0.1--0.3 mag brighter than the quiescent orbital modulation,
implying an optical precursor to the X-ray outburst. There is also a hint of a
gradual optical decay (years) followed by a rise lasting two months prior to
the outburst. We fortuitously obtained an optical spectrum of V404 Cyg 13 hours
before the BAT trigger. This too was brighter () than
quiescence, and showed spectral lines typical of an accretion disk, with
characteristic absorption features of the donor being much weaker. No He II
emission was detected, which would have been expected had the X-ray flux been
substantially brightening. This, combined with the presence of intense
H emission, about 7 times the quiescent level, suggests that the disk
entered the hot, outburst state before the X-ray outburst began. We propose
that the outburst is produced by a viscous-thermal instability triggered close
to the inner edge of a truncated disk. An X-ray delay of a week is consistent
with the time needed to refill the inner region and hence move the inner edge
of the disk inwards, allowing matter to reach the central BH, finally turning
on the X-ray emission.Comment: Accepted by ApJ Letter, 7 pages, 5 figure
An Infrared Determination of the Reddening and Distance to Dwingeloo 1
We present for the first time infrared observations of the nearby highly
obscured galaxy Dwingeloo 1 (Dw1), including deep H-band imaging covering a
total of 4.9x4.9 arcmin, together with J and Ks imaging of the central 2.5x2.5
arcmin. We used the small dispersion of the intrinsic infrared colors of spiral
galaxies to determine an infrared H-band extinction of A_H = 0.47+/-0.11 mag
towards Dw1. In using infrared colors, the uncertainties in the reddening and
distance are reduced by a factor of three. The H-band magnitude corrected for
extinction and the infrared Tully-Fisher relation are then used to estimate a
distance modulus of (m-M)_0 = 28.62+/-0.27, and thus a distance of d = 5.3
{+0.7/-0.6} Mpc, which puts Dw1 at the far end of the IC342/Maffei 1 & 2 group.
Our result is largely independent of the nature of the reddening law because we
estimated both the reddening and the distance at the same wavelength range.Comment: 20 pages, 2 figures, see
http://nicmos2.as.arizona.edu/~aalonso/Dw1/dw1_paper.htm
Entanglement between more than two hundred macroscopic atomic ensembles in a solid
We create a multi-partite entangled state by storing a single photon in a
crystal that contains many large atomic ensembles with distinct resonance
frequencies. The photon is re-emitted at a well-defined time due to an
interference effect analogous to multi-slit diffraction. We derive a lower
bound for the number of entangled ensembles based on the contrast of the
interference and the single-photon character of the input, and we
experimentally demonstrate entanglement between over two hundred ensembles,
each containing a billion atoms. In addition, we illustrate the fact that each
individual ensemble contains further entanglement. Our results are the first
demonstration of entanglement between many macroscopic systems in a solid and
open the door to creating even more complex entangled states.Comment: 10 pages, 8 figures; see also parallel submission by Frowis et a
The Influence of Bars on Nuclear Activity
We test ideas on fueling of galactic nuclei by bar-driven inflow by comparing
the detection rate and intensity of nuclear H II regions and AGNs among barred
and unbarred galaxies in a sample of over 300 spirals selected from our recent
optical spectroscopic survey of nearby galaxies. Among late-type spirals
(Sc-Sm), but not early-type (S0/a-Sbc), we observe in the barred group a very
marginal increase in the detection rate of H II nuclei and a corresponding
decrease in the incidence of AGNs. The minor differences in the detection
rates, however, are statistically insignificant, most likely stemming from
selection effects and not from a genuine influence from the bar. The presence
of a bar seems to have no noticeable impact on the likelihood of a galaxy to
host either nuclear star formation or an AGN. The nuclei of early-type barred
spirals do exhibit measurably higher star-formation rates than their unbarred
counterparts, as indicated by either the luminosity or the equivalent width of
H-alpha emission. By contrast, late-type spirals do not show such an effect.
Bars have a negligible effect on the strength of the AGNs in our sample,
regardless of the Hubble type of the host galaxy. This result confirms similar
conclusions reached by other studies based on much smaller samples.Comment: To appear in the Astrophysical Journal. LaTex, 31 pages including 6
postscript figures and 3 tables. AAStex macros include
VHE Gamma Rays from PKS 2155-304
The close X-ray selected BL Lac PKS 2155-304 has been observed using the
University of Durham Mark 6 very high energy (VHE) gamma ray telescope during
1996 September/October/November and 1997 October/November. VHE gamma rays with
energy > 300 GeV were detected from this object with a time-averaged integral
flux of (4.2 +/- 0.7 (stat) +/- 2.0 (sys)) x 10^(-11) per cm2 per s. There is
evidence for VHE gamma ray emission during our observations in 1996 September
and 1997 October/November, with the strongest emission being detected in 1997
November, when the object was producing the largest flux ever recorded in
high-energy X-rays and was detected in > 100 MeV gamma-rays. The VHE and X-ray
fluxes show evidence of a correlation.Comment: 14 pages, 6 figures, accepted for publication in Ap.
Parallel algorithm with spectral convergence for nonlinear integro-differential equations
We discuss a numerical algorithm for solving nonlinear integro-differential
equations, and illustrate our findings for the particular case of Volterra type
equations. The algorithm combines a perturbation approach meant to render a
linearized version of the problem and a spectral method where unknown functions
are expanded in terms of Chebyshev polynomials (El-gendi's method). This
approach is shown to be suitable for the calculation of two-point Green
functions required in next to leading order studies of time-dependent quantum
field theory.Comment: 15 pages, 9 figure
NMA CO (J=1-0) Observations of the Halpha/Radio Lobe Galaxy NGC 3079: Gas Dynamics in a Weak Bar Potential and Central Massive Core
within 24 lines with 80 characters) We present ^12CO (1-0) observations in
the central 4.5 kpc (1 arcmin) of the Halpha/Radio lobe galaxy NGC 3079 with
the Nobeyama Millimeter Array. The molecular gas shows four components: a main
disk, spiral arms, a nuclear disk, and a nuclear core. The main disk extends
beyond our spatial coverage. The spiral arms are superimposed on the main disk.
The nuclear disk with about 600 pc radius has an intense concentration of
molecular gas. Its appearance on PV diagrams is indicative of oval motions of
the gas, rather than circular. The nuclear core is more compact than our
resolution. Though it is unresolved, the nuclear core shows a very high
velocity about 200 km/s even at the radius of about 100 pc on the PV diagram.
We propose a model that NGC 3079 contains a weak bar. This model explains the
observed features: the main disk and spiral arms result from gaseous x1-orbits
and associated crowding respectively. The nuclear disk arises from gaseous
x2-orbits. From the appearance of the spiral arms on the PV diagram, the
pattern speed of the bar is estimated to be 55+-10 km/s/kpc. The high velocity
of the nuclear core cannot be explained by our model for a bar. Thus we
attribute it to a central massive core with a dynamical mass of 10^9 Msun
within the central 100 pc. This mass is three orders of magnitude more massive
than that of a central black hole in this galaxy.Comment: 43 pages, 17 figures; ApJ, 573, 105, 200
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