449 research outputs found
Speract induces calcium oscillations in the sperm tail
Sea urchin sperm motility is modulated by sperm-activating peptides. One such peptide, speract, induces changes in intracellular free calcium concentration ([Ca2+]i). High resolution imaging of single sperm reveals that speract-induced changes in [Ca2+]i have a complex spatiotemporal structure. [Ca2+]i increases arise in the tail as periodic oscillations; [Ca2+]i increases in the sperm head lag those in the tail and appear to result from the summation of the tail signal transduction events. The period depends on speract concentration. Infrequent spontaneous [Ca2+]i transients were also seen in the tail of unstimulated sperm, again with the head lagging the tail. Speract-induced fluctuations were sensitive to membrane potential and calcium channel blockers, and were potentiated by niflumic acid, an anion channel blocker. 3-isobutyl-1-methylxanthine, which potentiates the cGMP/cAMP-signaling pathways, abolished the [Ca2+]i fluctuations in the tail, leading to a very delayed and sustained [Ca2+]i increase in the head. These data point to a model in which a messenger generated periodically in the tail diffuses to the head. Sperm are highly polarized cells. Our results indicate that a clear understanding of the link between [Ca2+]i and sperm motility will only be gained by analysis of [Ca2+]i signals at the level of the single sperm
Star Formation at z=2.481 in the Lensed Galaxy SDSS J1110+6459, I: Lens Modeling and Source Reconstruction
Using the combined resolving power of the Hubble Space Telescope and
gravitational lensing, we resolve star-forming structures in a z~2.5 galaxy on
scales much smaller than the usual kiloparsec diffraction limit of HST. SGAS
J111020.0+645950.8 is a clumpy, star forming galaxy lensed by the galaxy
cluster SDSS J1110+6459 at z = 0.659, with a total magnification ~30x across
the entire arc. We use a hybrid parametric/non-parametric strong lensing mass
model to compute the deflection and magnification of this giant arc,
reconstruct the light distribution of the lensed galaxy in the source plane,
and resolve the star formation into two dozen clumps. We develop a
forward-modeling technique to model each clump in the source plane. We ray
trace the model to the image plane, convolve with the instrumental point spread
function (PSF), and compare with the GALFIT model of the clumps in the image
plane, which decomposes clump structure from more extended emission. This
technique has the advantage, over ray tracing, by accounting for the asymmetric
lensing shear of the galaxy in the image plane and the instrument PSF. At this
resolution, we can begin to study star formation on a clump-by-clump basis,
toward the goal of understanding feedback mechanisms and the buildup of
exponential disks at high redshift.Comment: 19 pages, 12 figures, accepted to Ap
Lens Model and Time Delay Predictions for the Sextuply Lensed Quasar SDSS J2222+2745
SDSS J2222+2745 is a galaxy cluster at z=0.49, strongly lensing a quasar at
z=2.805 into six widely separated images. In recent HST imaging of the field,
we identify additional multiply lensed galaxies, and confirm the sixth quasar
image that was identified by Dahle et al. (2013). We used the Gemini North
telescope to measure a spectroscopic redshift of z=4.56 of one of the secondary
lensed galaxies. These data are used to refine the lens model of SDSS
J2222+2745, compute the time delay and magnifications of the lensed quasar
images, and reconstruct the source image of the quasar host and a second lensed
galaxy at z=2.3. This second galaxy also appears in absorption in our Gemini
spectra of the lensed quasar, at a projected distance of 34 kpc. Our model is
in agreement with the recent time delay measurements of Dahle et al. (2015),
who found tAB=47.7+/-6.0 days and tAC=-722+/-24 days. We use the observed time
delays to further constrain the model, and find that the model-predicted time
delays of the three faint images of the quasar are tAD=502+/-68 days,
tAE=611+/-75 days, and tAF=415+/-72 days. We have initiated a follow-up
campaign to measure these time delays with Gemini North. Finally, we present
initial results from an X-ray monitoring program with Swift, indicating the
presence of hard X-ray emission from the lensed quasar, as well as extended
X-ray emission from the cluster itself, which is consistent with the lensing
mass measurement and the cluster velocity dispersion.Comment: 16 pages, 11 figures; submitted to Ap
Examination of local movement and migratory behavior of sea turtles during spring and summer along the Atlantic Coast off the Southeastern United States : annual report.
Loggerhead sea turtles inhabiting coastal waters along the southeastern United States represent the progeny of multiple rookeries. Tagging studies of nesting female loggerheads suggest that most return to the same beaches in successive breeding seasons and it is widely accepted that most females return to their natal regions to nest.
The focus of the in-water survey was modified to intensively target one small trawling area to: (1) examine the effect of intensive trawling on recapture rates and (2) quickly obtain an adequate sample size of turtles to outfit with satellite transmitters. This annual report highlights the major findings for research activities primarily carried
out during 2005
Strong Lens Models for 37 Clusters of Galaxies from the SDSS Giant Arcs Survey
We present strong gravitational lensing models for 37 galaxy clusters from
the SDSS Giant Arcs Survey. We combine data from multi-band Hubble Space
Telescope WFC3imaging, with ground-based imaging and spectroscopy from
Magellan, Gemini, APO, and MMT, in order to detect and spectroscopically
confirm new multiply-lensed background sources behind the clusters. We report
spectroscopic or photometric redshifts of sources in these fields, including
cluster galaxies and background sources. Based on all available lensing
evidence, we construct and present strong lensing mass models for these galaxy
clusters.Comment: 53 pages; submitted to ApJ
Push or delay? Decomposing Smartphone notification response behaviour
Smartphone notifications are often delivered without considering user interruptibility, potentially causing frustration for the recipient. Therefore research in this area has concerned finding contexts where interruptions are better received. The typical convention for monitoring interruption behaviour assumes binary actions, where a response is either completed or not at all. However, in reality a user may partially respond to an interruption, such as reacting to an audible alert or exploring which application caused it. Consequently we present a multi-step model of interruptibility that allows assessment of both partial and complete notification responses. Through a 6-month in-the-wild case study of 11,346 to-do list reminders from 93 users, we find support for reducing false-negative classification of interruptibility. Additionally, we find that different response behaviour is correlated with different contexts and that these behaviours are predictable with similar accuracy to complete responses
Interruptibility prediction for ubiquitous systems: conventions and new directions from a growing field
When should a machine attempt to communicate with a user? This is a historical problem that has been studied since the rise of personal computing. More recently, the emergence of pervasive technologies such as the smartphone have extended the problem to be ever-present in our daily lives, opening up new opportunities for context awareness through data collection and reasoning. Complementary to this there has been increasing interest in techniques to intelligently synchronise interruptions with human behaviour and cognition. However, it is increasingly challenging to categorise new developments, which are often scenario specific or scope a problem with particular unique features. In this paper we present a meta-analysis of this area, decomposing and comparing historical and recent works that seek to understand and predict how users will perceive and respond to interruptions. In doing so we identify research gaps, questions and opportunities that characterise this important emerging field for pervasive technology
Star Formation at z = 2.481 in the Lensed Galaxy SDSS J1110+6459: Star Formation Down to 30 pc Scales
We present measurements of the surface density of star formation, the star-forming clump luminosity function, and the clump size distribution function, for the lensed galaxy SGAS J111020.0+645950.8 at a redshift of z =2.481. The physical size scales that we probe, radii r = 30-50 pc, are considerably smaller scales than have yet been studied at these redshifts. The star formation surface density we find within these small clumps is consistent with surface densities measured previously for other lensed galaxies at similar redshift. Twenty-two percent of the rest-frame ultraviolet light in this lensed galaxy arises from small clumps, with r is less than 100 pc. Within the range of overlap, the clump luminosity function measured for this lensed galaxy is remarkably similar to those of z is approximately 0 galaxies. In this galaxy, star-forming regions smaller than 100 pc-physical scales not usually resolved at these redshifts by current telescopes-are important locations of star formation in the distant universe. If this galaxy is representative, this may contradict the theoretical picture in which the critical size scale for star formation in the distant universe is of order 1 kiloparsec. Instead, our results suggest that current telescopes have not yet resolved the critical size scales of star-forming activity in galaxies over most of cosmic time
Lens Model and Source Reconstruction Reveal the Morphology and Star Formation Distribution in the Cool Spiral LIRG SGAS J143845.1145407
We present () imaging and grism spectroscopy
of a strongly lensed LIRG at , SGAS 143845.1145407, and use the
magnification boost of gravitational lensing to study the distribution of star
formation throughout this galaxy. Based on the imaging data, we create a
lens model for this system; we compute the mass distribution and magnification
map of the foreground lens. We find that the magnification of the
lensed galaxy ranges between and , with a total magnification (measured
over all the images of the source) of . We find that
the total projected mass density within kpc of the brightest cluster
galaxy is . Using the lens model we
create a source reconstruction for SGAS 143845.1145407, which paired with a
faint detection of H in the grism spectroscopy, allows us to finally
comment directly on the distribution of star formation in a LIRG. We
find widespread star formation across this galaxy, in agreement with the
current understanding of these objects. However, we note a deficit of H
emission in the nucleus of SGAS 143845.1145407, likely due to dust
extinction.Comment: 7 pages, 8 figures, 2 table
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