2,471 research outputs found
Towards A Census of Earth-mass Exo-planets with Gravitational Microlensing
Thirteen exo-planets have been discovered using the gravitational
microlensing technique (out of which 7 have been published). These planets
already demonstrate that super-Earths (with mass up to ~10 Earth masses) beyond
the snow line are common and multiple planet systems are not rare. In this
White Paper we introduce the basic concepts of the gravitational microlensing
technique, summarise the current mode of discovery and outline future steps
towards a complete census of planets including Earth-mass planets. In the
near-term (over the next 5 years) we advocate a strategy of automated follow-up
with existing and upgraded telescopes which will significantly increase the
current planet detection efficiency. In the medium 5-10 year term, we envision
an international network of wide-field 2m class telescopes to discover
Earth-mass and free-floating exo-planets. In the long (10-15 year) term, we
strongly advocate a space microlensing telescope which, when combined with
Kepler, will provide a complete census of planets down to Earth mass at almost
all separations. Such a survey could be undertaken as a science programme on
Euclid, a dark energy probe with a wide-field imager which has been proposed to
ESA's Cosmic Vision Programme.Comment: 10 pages. White Paper submission to the ESA Exo-Planet Roadmap
Advisory Team. See also "Inferring statistics of planet populations by means
of automated microlensing searches" by M. Dominik et al. (arXiv:0808.0004
Detection of chromatic and luminance distortions in natural scenes
A number of studies have measured visual thresholds for detecting spatial distortions applied to images of natural scenes. In one study, Bex (2010) measured sensitivity to sinusoidal spatial modulations of image scale. Here we measure sensitivity to sinusoidal scale distortions applied to the chromatic, luminance or both layers of natural scene images. We first established that sensitivity does not depend on whether the undistorted comparison image was of the same or of a different scene. Next we found that when the luminance but not chromatic layer was distorted, performance was the same irrespective of whether the chromatic layer was present, absent or phase scrambled; in other words the chromatic layer, in whatever form, did not affect sensitivity to luminance-layer distortion. However when the chromatic layer was distorted, sensitivity was higher when the luminance layer was intact compared to when absent or phase-scrambled. These detection threshold results complement the appearance of periodic distortions of image scale: when the luminance layer is visibly distorted, the scene appears distorted, but when the chromatic layer is visibly distorted, there is little apparent scene distortion. We conclude that (a) observers have an in-built sense of how a normal image of a natural scene should appear, and (b) the detection of distortion in, as well as the apparent distortion of natural-scene images is mediated predominantly by the luminance not chromatic laye
The historical vanishing of the Blazhko effect of RR Lyr from GEOS and Kepler surveys
RR Lyr is one of the most studied variable stars. Its light curve has been
regularly monitored since the discovery of the periodic variability in 1899.
Analysis of all observed maxima allows us to identify two primary pulsation
states defined as pulsation over a long (P0 longer than 0.56684 d) and a short
(P0 shorter than 0.56682 d) primary pulsation period. These states alternate
with intervals of 13-16 yr, and are well defined after 1943. The 40.8 d
periodical modulations of the amplitude and the period (i.e. Blazhko effect)
were noticed in 1916. We provide homogeneous determinations of the Blazhko
period in the different primary pulsation states. The Blazhko period does not
follow the variations of P0 and suddenly diminished from 40.8 d to around 39.0
d in 1975. The monitoring of these periodicities deserved and deserves a
continuous and intensive observational effort. For this purpose we have built
dedicated, transportable and autonomous small instruments, Very Tiny Telescopes
(VTTs), to observe the times of maximum brightness of RR Lyr. As immediate
results the VTTs recorded the last change of P0 state in mid-2009 and extended
the time coverage of the Kepler observations, thus recording a maximum O-C
amplitude of the Blazhko effect at the end of 2008, followed by the
historically smallest O-C amplitude in late 2013. This decrease is still
ongoing and VTT instruments are ready to monitor the expected increase in the
next few years.Comment: 10 pages, 6 figures. Accepted for publication in MNRAS. Contents of
appendix B may be requested to first autho
Design and Synthesis of Broad Spectrum Trypanosomatid Selective Inhibitors
Neglected
tropical diseases caused by parasitic infections are an ongoing and
increasing concern that have a devastating effect on the developing
world due to their burden on human and animal health. In this work,
we detail the preparation of a focused library of substituted-tetrahydropyran
derivatives and their evaluation as selective chemical tools for trypanosomatid
inhibition and the follow-on development of photoaffinity probes capable
of labeling target protein(s) <i>in vitro</i>. Several of
these functionalized compounds maintain low micromolar activity against <i>Trypanosoma brucei</i>, <i>Trypanosoma cruzi</i>, <i>Leishmania major</i>, and <i>Leishmania donovani</i>. In addition, we demonstrate the utility of the photoaffinity probes
for target identification through preliminary cellular localization
studies
Optimisation of energetic and reproductive gains explains behavioural responses to environmental variation across seasons and years
Animals switch between inactive and active states, simultaneously impacting their energy intake, energy expenditure and predation risk, and collectively defining how they engage with environmental variation and trophic interactions. We assess daily activity responses to long‐term variation in temperature, resources and mating opportunities to examine whether individuals choose to be active or inactive according to an optimisation of the relative energetic and reproductive gains each state offers. We show that this simplified behavioural decision approach predicts most activity variation (R2 = 0.83) expressed by free‐ranging red squirrels over 4 years, as quantified through accelerometer recordings (489 deployments; 5066 squirrel‐days). Recognising activity as a determinant of energetic status, the predictability of activity variation aggregated at a daily scale, and the clear signal that behaviour is environmentally forced through optimisation of gain, provides an integrated approach to examine behavioural variation as an intermediary between environmental variation and energetic, life‐history and ecological outcomes.By assessing daily activity responses to long‐term variation in temperature, resources, and mating opportunities, we examine whether individuals choose to be active or inactive according to an optimization of energetic and reproductive gains. This simplified behavioural decision approach predicts most daily activity variation (R2 = 0.83) expressed by free‐ranging red squirrels over four years, as quantified through accelerometer recordings. Here we provide an integrated approach to examine behavioural variation as an intermediary between environmental variation and energetic, life‐history, and ecological outcomes.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154889/1/ele13494_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154889/2/ele13494.pd
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