8,849 research outputs found
Four-dimensional worldwide atmospheric models: ANYPT and ANYRG
Computer programs read magnetic-tape data bases and computer meteorological profiles for any position, time, and height (from zero to 25 km). System assists in analyses of distortion of information obtained from aircraft-mounted or spacecraft-mounted electromagnetic sensors
Deuce: A Lightweight User Interface for Structured Editing
We present a structure-aware code editor, called Deuce, that is equipped with
direct manipulation capabilities for invoking automated program
transformations. Compared to traditional refactoring environments, Deuce
employs a direct manipulation interface that is tightly integrated within a
text-based editing workflow. In particular, Deuce draws (i) clickable widgets
atop the source code that allow the user to structurally select the
unstructured text for subexpressions and other relevant features, and (ii) a
lightweight, interactive menu of potential transformations based on the current
selections. We implement and evaluate our design with mostly standard
transformations in the context of a small functional programming language. A
controlled user study with 21 participants demonstrates that structural
selection is preferred to a more traditional text-selection interface and may
be faster overall once users gain experience with the tool. These results
accord with Deuce's aim to provide human-friendly structural interactions on
top of familiar text-based editing.Comment: ICSE 2018 Paper + Supplementary Appendice
The importance of nuclear masses in the astrophysical rp-process
The importance of mass measurements for astrophysical capture processes in
general, and for the rp-process in X-ray bursts in particular is discussed. A
review of the current uncertainties in the effective lifetimes of the major
waiting points 64Ge, 68Se, and 72Kr demonstrates that despite of recent
measurements uncertainties are still significant. It is found that mass
measurements with an accuracy of the order of 10 keV or better are desirable,
and that reaction rate uncertainties play a critical role as well.Comment: 14 pages, 4 figures, to appear in International Journal of Mass
Spectroscop
C*-algebras associated to boolean dynamical systems
The goal of these notes is to present the C*-algebra C*(B,L,θ) of a Boolean dynamical system (B,L,θ), that generalizes the C*-algebra associated to Labelled graphs introduced by Bates and Pask, and to determine its simplicity, its gauge invariant ideals, as well as compute its K-Theory
Stellar Abundances in the Early Galaxy and Two r-Process Components
We present quantitative predictions for the abundances of r-process elements
in stars formed very early in the Galactic history using a phenomenological
two-component r-process model based on the I129 and Hf182 inventory in the
early solar system. This model assumes that a standard mass of the ISM dilutes
the debris from an individual supernova. High frequency supernova H events and
low frequency supernova L events are proposed in the model with characteristics
determined by the meteoritic data on I129 and Hf182. The yields in an H or L
event are obtained from these characteristics and the solar r-process
abundances under the assumption that the yield template for the high mass (A >
130) nuclei associated with W182 or the low mass (A < or = 130) nuclei
associated with I127 is the same for both the H and L events and follows the
corresponding solar r-pattern in each mass region. The abundance of Eu, not Fe,
is proposed as a key guide to the age of very metal-poor stars. We predict that
stars with log epsilon (Eu) = -2.98 to -2.22 were formed from an ISM
contaminated most likely by a single H event within the first 10**7 yr of the
Galactic history and should have an Ag/Eu abundance ratio less than the
corresponding solar r-process value by a factor of at least 10. Many of the
very metal-poor stars observed so far are considered here to have been formed
from an ISM contaminated by many (about 10) r-process events. Stars formed from
an ISM contaminated only by a pure L event would have an Ag/Eu ratio higher
than the corresponding solar r-process value but would be difficult to find due
to the low frequency of the L events. However, variations in the relative
abundances of the low and high mass regions should be detectable in very
metal-poor stars.Comment: 46 pages, 19 figures, to appear in the Schramm Memorial Volume of
Physics Report
Purely infinite simple C*-algebras that are principal groupoid C*-algebras
From a suitable groupoid G, we show how to construct an amenable principal
groupoid whose C*-algebra is a Kirchberg algebra which is KK-equivalent to
C*(G). Using this construction, we show by example that many UCT Kirchberg
algebras can be realised as the C*-algebras of amenable principal groupoids.Comment: 20 pages, 1 picture prepared using Tik
Preserving the palaeoenvironmental record in Drylands: Bioturbation and its significance for luminescence-derived chronologies
Luminescence (OSL) dating has revolutionised the understanding of Late Pleistocene dryland activity. However,
one of the key assumptions for this sort of palaeoenvironmental work is that sedimentary sequences have been
preserved intact, enabling their use as proxy indicators of past changes. This relies on stabilisation or burial
soon after deposition and a mechanism to prevent any subsequent re-mobilisation. As well as a dating
technique OSL, especially at the single grain level, can be used to gain an insight into post-depositional
processes that may distort or invalidate the palaeoenvironmental record of geological sediment sequences.
This paper explores the possible impact of bioturbation (the movement of sediment by flora and fauna) on
luminescence derived chronologies from Quaternary sedimentary deposits in Texas and Florida (USA) which
have both independent radiocarbon chronologies and archaeological evidence. These sites clearly illustrate the
ability of bioturbation to rejuvenate ancient weathered sandy bedrock and/or to alter depositional stratigraphies
through the processes of exhumation and sub-surface mixing of sediment. The use of multiple OSL replicate
measurements is advocated as a strategy for checking for bioturbated sediment. Where significant OSL
heterogeneity is found, caution should be taken with the derived OSL ages and further measurements at the
single grain level are recommended. Observations from the linear dunes of the Kalahari show them to have no
bedding structure and to have OSL heterogeneity similar to that shown from the bioturbated Texan and Florida
sites. The Kalahari linear dunes could have therefore undergone hitherto undetected post-depositional sediment
disturbance which would have implications for the established OSL chronology for the region
First Order Quark-Gluon/Hadron Transition May Affect Cosmological Nucleosynthesis
In the model of a first order quark-gluon/hadron phase transition in which
the hadronic phase is considered as vacuum bubbles growing in the quark-gluon
background with chiral symmetry broken inside the bubble, we find the estimate
for the length scale associated with inhomogeneities originated during the
transition, m m, being
sufficient to produce significant effects on cosmological nucleosynthesis.Comment: 10 pages, LaTeX, to appear in Phys. Lett. B, 199
Optical Design of the Atacama Cosmology Telescope and the Millimeter Bolometric Array Camera
The Atacama Cosmology Telescope is a 6-meter telescope designed to map the
Cosmic Microwave Background simultaneously at 145 GHz, 215 GHz, and 280 GHz
with arcminute resolution. Each frequency will have a 32 by 32 element focal
plane array of TES bolometers. This paper describes the design of the telescope
and the cold reimaging optics, which is optimized for millimeter-wave
observations with these sensitive detectors.Comment: 23 pages. Accepted for publication in Applied Optics. Several minor
clarifications added after peer revie
Scientific impact evaluation and the effect of self-citations: mitigating the bias by discounting h-index
In this paper, we propose a measure to assess scientific impact that
discounts self-citations and does not require any prior knowledge on the their
distribution among publications. This index can be applied to both researchers
and journals. In particular, we show that it fills the gap of h-index and
similar measures that do not take into account the effect of self-citations for
authors or journals impact evaluation. The paper provides with two real-world
examples: in the former, we evaluate the research impact of the most productive
scholars in Computer Science (according to DBLP); in the latter, we revisit the
impact of the journals ranked in the 'Computer Science Applications' section of
SCImago. We observe how self-citations, in many cases, affect the rankings
obtained according to different measures (including h-index and ch-index), and
show how the proposed measure mitigates this effect
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