745 research outputs found
Saturn sa-9/pegasus a postflight trajectory
Postflight trajectory analysis and orbital flight discussion for Saturn I /SA- 9/ launch vehicle carrying Pegasus payloa
Subsampling in Smoothed Range Spaces
We consider smoothed versions of geometric range spaces, so an element of the
ground set (e.g. a point) can be contained in a range with a non-binary value
in . Similar notions have been considered for kernels; we extend them to
more general types of ranges. We then consider approximations of these range
spaces through -nets and -samples (aka
-approximations). We characterize when size bounds for
-samples on kernels can be extended to these more general
smoothed range spaces. We also describe new generalizations for -nets to these range spaces and show when results from binary range spaces can
carry over to these smoothed ones.Comment: This is the full version of the paper which appeared in ALT 2015. 16
pages, 3 figures. In Algorithmic Learning Theory, pp. 224-238. Springer
International Publishing, 201
The total rest-frame UV luminosity function from 3 < z < 5: a simultaneous study of AGN and galaxies from −28 < MUV < −16
We present measurements of the rest-frame ultraviolet luminosity function (LF) at redshifts z = 3, z = 4, and z = 5, using 96894, 38655, and 7571 sources, respectively, to map the transition between active galactic nuclei (AGN) and galaxy-dominated ultraviolet emission shortly after the epoch of reionization (EoR). Sources are selected using a comprehensive photometric redshift approach, using 10 deg2 of deep extragalactic legacy fields covered by both HSC and VISTA. The use of template fitting spanning a wavelength range of 0.3–2.4 μm achieves 80–90 per cent completeness, much higher than the classical colour–colour cut methodology. The measured LF encompasses −26 < MUV < −19.25. This is further extended to −28.5 < MUV < −16 using complementary results from other studies, allowing for the simultaneous fitting of the combined AGN and galaxy LF. We find that there are fewer UV luminous galaxies (MUV < −22) at z ∼ 3 than z ∼ 4, indicative of an onset of widespread quenching alongside dust obscuration, and that the evolution of the AGN LF is very rapid, with their number density rising by around two orders of magnitude from 3 < z < 6. It remains difficult to determine if a double power law functional form is preferred over the Schechter function to describe the galaxy UV LF. Estimating the hydrogen ionizing photon budget from our UV LFs, we find that AGN can contribute to, but cannot solely maintain, the reionization of the Universe at z = 3–5. However, the rapidly evolving AGN LF strongly disfavours a significant contribution within the EoR
The bright end of the galaxy luminosity function at z ≃ 7 from the VISTA VIDEO survey
We have conducted a search for z ≃ 7 Lyman-break galaxies over 8.2 deg2 of near-infrared imaging from the Visible and Infrared Survey Telescope for Astronomy (VISTA) Deep Extragalactic Observations (VIDEO) survey in the XMM–Newton-Large Scale Structure (XMM-LSS) and the Extended Chandra Deep Field-South (ECDF-S) fields. Candidate galaxies were selected from a full photometric redshift analysis down to a Y + J depth of 25.3 (5σ), utilizing deep auxiliary optical and Spitzer/Infrared Array Camera (IRAC) data to remove brown dwarf and red interloper galaxy contaminants. Our final sample consists of 28 candidate galaxies at 6.5 ≤ z ≤ 7.5 with −23.5 ≤ MUV ≤ −21.6. We derive stellar masses of 9.1 ≤ log10(M⋆/M⊙) ≤ 10.9 for the sample, suggesting that these candidates represent some of the most massive galaxies known at this epoch. We measure the rest-frame ultraviolet (UV) luminosity function (LF) at z ≃ 7, confirming previous findings of a gradual decline in number density at the bright end (MUV 5 samples, our results further support little evolution in the very bright end of the rest-frame UV LF from z = 5–10, potentially signalling a lack of mass quenching and/or dust obscuration in the most massive galaxies in the first Gyr
Retarded Learning: Rigorous Results from Statistical Mechanics
We study learning of probability distributions characterized by an unknown
symmetry direction. Based on an entropic performance measure and the
variational method of statistical mechanics we develop exact upper and lower
bounds on the scaled critical number of examples below which learning of the
direction is impossible. The asymptotic tightness of the bounds suggests an
asymptotically optimal method for learning nonsmooth distributions.Comment: 8 pages, 1 figur
Feather development genes and associated regulatory innovation predate the origin of Dinosauria
The evolution of avian feathers have recently been illuminated by fossils and the identification of genes involved in feather patterning and morphogenesis. However, molecular studies have focused mainly on protein-coding genes. Using comparative genomics and more than 600,000 conserved regulatory elements, we show that patterns of genome evolution in the vicinity of feather genes are consistent with a major role for regulatory innovation in the evolution of feathers. Rates of innovation at feather regulatory elements exhibit an extended period of innovation with peaks in the ancestors of amniotes and archosaurs. We estimate that 86% of such regulatory elements were present prior to the origin of Dinosauria. On the branch leading to modern birds, we detect a strong signal of regulatory innovation near IGFBP2 and IGFBP5, which have roles in body size reduction, and may represent a genomic signature for the miniaturization of dinosaurian body size preceding the origin of flight.Organismic and Evolutionary Biolog
Prediction with Expert Advice under Discounted Loss
We study prediction with expert advice in the setting where the losses are
accumulated with some discounting---the impact of old losses may gradually
vanish. We generalize the Aggregating Algorithm and the Aggregating Algorithm
for Regression to this case, propose a suitable new variant of exponential
weights algorithm, and prove respective loss bounds.Comment: 26 pages; expanded (2 remarks -> theorems), some misprints correcte
Unsplittable coverings in the plane
A system of sets forms an {\em -fold covering} of a set if every point
of belongs to at least of its members. A -fold covering is called a
{\em covering}. The problem of splitting multiple coverings into several
coverings was motivated by classical density estimates for {\em sphere
packings} as well as by the {\em planar sensor cover problem}. It has been the
prevailing conjecture for 35 years (settled in many special cases) that for
every plane convex body , there exists a constant such that every
-fold covering of the plane with translates of splits into
coverings. In the present paper, it is proved that this conjecture is false for
the unit disk. The proof can be generalized to construct, for every , an
unsplittable -fold covering of the plane with translates of any open convex
body which has a smooth boundary with everywhere {\em positive curvature}.
Somewhat surprisingly, {\em unbounded} open convex sets do not misbehave,
they satisfy the conjecture: every -fold covering of any region of the plane
by translates of such a set splits into two coverings. To establish this
result, we prove a general coloring theorem for hypergraphs of a special type:
{\em shift-chains}. We also show that there is a constant such that, for
any positive integer , every -fold covering of a region with unit disks
splits into two coverings, provided that every point is covered by {\em at
most} sets
Comparative Genomics Search for Losses of Long-Established Genes on the Human Lineage
Taking advantage of the complete genome sequences of several mammals, we developed a novel method to detect losses of well-established genes in the human genome through syntenic mapping of gene structures between the human, mouse, and dog genomes. Unlike most previous genomic methods for pseudogene identification, this analysis is able to differentiate losses of well-established genes from pseudogenes formed shortly after segmental duplication or generated via retrotransposition. Therefore, it enables us to find genes that were inactivated long after their birth, which were likely to have evolved nonredundant biological functions before being inactivated. The method was used to look for gene losses along the human lineage during the approximately 75 million years (My) since the common ancestor of primates and rodents (the euarchontoglire crown group). We identified 26 losses of well-established genes in the human genome that were all lost at least 50 My after their birth. Many of them were previously characterized pseudogenes in the human genome, such as GULO and UOX. Our methodology is highly effective at identifying losses of single-copy genes of ancient origin, allowing us to find a few well-known pseudogenes in the human genome missed by previous high-throughput genome-wide studies. In addition to confirming previously known gene losses, we identified 16 previously uncharacterized human pseudogenes that are definitive losses of long-established genes. Among them is ACYL3, an ancient enzyme present in archaea, bacteria, and eukaryotes, but lost approximately 6 to 8 Mya in the ancestor of humans and chimps. Although losses of well-established genes do not equate to adaptive gene losses, they are a useful proxy to use when searching for such genetic changes. This is especially true for adaptive losses that occurred more than 250,000 years ago, since any genetic evidence of the selective sweep indicative of such an event has been erased
Cosmological weak lensing with the HST GEMS survey
We present our cosmic shear analysis of GEMS, one of the largest wide-field
surveys ever undertaken by the Hubble Space Telescope. Imaged with the Advanced
Camera for Surveys (ACS), GEMS spans 795 square arcmin in the Chandra Deep
Field South. We detect weak lensing by large-scale structure in high resolution
F606W GEMS data from ~60 resolved galaxies per square arcminute. We measure the
two-point shear correlation function, the top-hat shear variance and the shear
power spectrum, performing an E/B mode decomposition for each statistic. We
show that we are not limited by systematic errors and use our results to place
joint constraints on the matter density parameter Omega_m and the amplitude of
the matter power spectrum sigma_8. We find sigma_8(Omega_m/0.3)^{0.65}=0.68 +/-
0.13 where the 1sigma error includes both our uncertainty on the median
redshift of the survey and sampling variance.
Removing image and point spread function (PSF) distortions are crucial to all
weak lensing analyses. We therefore include a thorough discussion on the degree
of ACS PSF distortion and anisotropy which we characterise directly from GEMS
data. Consecutively imaged over 20 days, GEMS data also allows us to
investigate PSF instability over time. We find that, even in the relatively
short GEMS observing period, the ACS PSF ellipticity varies at the level of a
few percent which we account for with a semi-time dependent PSF model. Our
correction for the temporal and spatial variability of the PSF is shown to be
successful through a series of diagnostic tests.Comment: 17 pages, 16 figures. Version accepted by MNRA
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