5,233 research outputs found
Impact and Recovery Process of Mini Flash Crashes: An Empirical Study
In an Ultrafast Extreme Event (or Mini Flash Crash), the price of a traded
stock increases or decreases strongly within milliseconds. We present a
detailed study of Ultrafast Extreme Events in stock market data. In contrast to
popular belief, our analysis suggests that most of the Ultrafast Extreme Events
are not primarily due to High Frequency Trading. In at least 60 percent of the
observed Ultrafast Extreme Events, the main cause for the events are large
market orders. In times of financial crisis, large market orders are more
likely which can be linked to the significant increase of Ultrafast Extreme
Events occurrences. Furthermore, we analyze the 100 trades following each
Ultrafast Extreme Events. While we observe a tendency of the prices to
partially recover, less than 40 percent recover completely. On the other hand
we find 25 percent of the Ultrafast Extreme Events to be almost recovered after
only one trade which differs from the usually found price impact of market
orders
The property for nilpotent quotients of generalized solvable Baumslag-Solitar groups
We say a group has property if the number of
twisted conjugacy classes is infinite for every automorphism of .
For such groups, the -nilpotency degree is the least integer such
that has property . In this work, we compute the
-nilpotency degree of all Generalized Solvable Baumslag-Solitar
groups . Moreover, we compute the lower central series of ,
write the nilpotent quotients as
semidirect products of finitely generated abelian groups and classify which
integer invertible matrices can be extended to automorphisms of .Comment: 11 page
Symmetric Edit Lenses: A New Foundation for Bidirectional Languages
Lenses are bidirectional transformations between pairs of connected structures capable of translating an edit on one structure into an edit on the other. Most of the extensive existing work on lenses has focused on the special case of asymmetric lenses, where one structures is taken as primary and the other is thought of as a projection or view. Some symmetric variants exist, where each structure contains information not present in the other, but these all lack the basic operation of composition. Additionally, existing accounts do not represent edits carefully, making incremental operation difficult or producing unsatisfactory synchronization candidates. We present a new symmetric formulation which works with descriptions of changes to structures, rather than with the structures themselves. We construct a semantic space of edit lenses between “editable structures”—monoids of edits with a partial monoid action for applying edits—with natural laws governing their behavior. We present generalizations of a number of known constructions on asymmetric lenses and settle some longstanding questions about their properties—in particular, we prove the existence of (symmetric monoidal) tensor products and sums and the non-existence of full categorical products and sums in a category of lenses. Universal algebra shows how to build iterator lenses for structured data such as lists and trees, yielding lenses for operations like mapping, filtering, and concatenation from first principles. More generally, we provide mapping combinators based on the theory of containers. Finally, we present a prototype implementation of the core theory and take a first step in addressing the challenge of translating between user gestures and the internal representation of edits
SUMO (Simulation of Urban MObility) - an open-source traffic simulation
As no exact model of traffic flow exists due to its high complexity and chaotic organisation, researchers mainly try to predict traffic using simulations. Within this field, many simulation packages exist and differ in their software architecture paradigm as well as in the models that describe traffic itself. We will introduce yet another system which, in contrast to most of the other simulation software packages, is available as on open-source programm and may therfore be extended in order to fit a researcher´s own needs and also be used as a reference testbed for new traffic models
Single-Cell Analysis Reveals Functionally Distinct Classes within the Planarian Stem Cell Compartment
Planarians are flatworms capable of regenerating any missing body region. This capacity is mediated by neoblasts, a proliferative cell population that contains pluripotent stem cells. Although population-based studies have revealed many neoblast characteristics, whether functionally distinct classes exist within this population is unclear. Here, we used high-dimensional single-cell transcriptional profiling from over a thousand individual neoblasts to directly compare gene expression fingerprints during homeostasis and regeneration. We identified two prominent neoblast classes that we named ζ (zeta) and σ (sigma). Zeta-neoblasts encompass
specified cells that give rise to an abundant postmitotic lineage including epidermal cells, and are
not required for regeneration. By contrast, sigma-neoblasts proliferate in response to injury,
possess broad lineage capacity, and can give rise to zeta-neoblasts. These findings present a new
view of planarian neoblasts, in which the population is comprised of two major and functionally
distinct cellular compartments.Human Frontier Science Program (Strasbourg, France)National Institutes of Health (U.S.) (Grant R01GM080639
A new population of recently quenched elliptical galaxies in the SDSS
We use the Sloan Digital Sky Survey to investigate the properties of massive
elliptical galaxies in the local Universe (z\leq0.08) that have unusually blue
optical colors. Through careful inspection, we distinguish elliptical from
non-elliptical morphologies among a large sample of similarly blue galaxies
with high central light concentrations (c_r\geq2.6). These blue ellipticals
comprise 3.7 per cent of all c_r\geq2.6 galaxies with stellar masses between
10^10 and 10^11 h^{-2} {\rm M}_{\sun}. Using published fiber spectra
diagnostics, we identify a unique subset of 172 non-star-forming ellipticals
with distinctly blue urz colors and young (< 3 Gyr) light-weighted stellar
ages. These recently quenched ellipticals (RQEs) have a number density of
2.7-4.7\times 10^{-5}\,h^3\,{\rm Mpc}^{-3} and sufficient numbers above
2.5\times10^{10} h^{-2} {\rm M}_{\sun} to account for more than half of the
expected quiescent growth at late cosmic time assuming this phase lasts 0.5
Gyr. RQEs have properties that are consistent with a recent merger origin
(i.e., they are strong `first-generation' elliptical candidates), yet few
involved a starburst strong enough to produce an E+A signature. The preferred
environment of RQEs (90 per cent reside at the centers of < 3\times
10^{12}\,h^{-1}{\rm M}_{\sun} groups) agrees well with the `small group scale'
predicted for maximally efficient spiral merging onto their halo center and
rules out satellite-specific quenching processes. The high incidence of Seyfert
and LINER activity in RQEs and their plausible descendents may heat the
atmospheres of small host halos sufficiently to maintain quenching.Comment: 26 pages, 9 figures. Revised version; accepted for publication in
MNRA
Disputatio on the Distinction between the Human Person and Other Animals: the Human Person as Gardener
While the Catholic intellectual tradition upholds the uniqueness of humans, much contemporary scientific research has come to the opposing conclusion that humans are not significantly different from other animals. To engage in robust dialogue around the question of human uniqueness, we utilize Aquinas’s model of disputatio to focus on an attribute of human beings that is unexplored in the literature – namely, the human capacity to garden – and address five scientific and philosophical objections to our position that the capacity to garden makes humans distinct. Engaging with various branches of science, we demonstrate that human capacities and modes of gardening are not only incrementally different, but also fundamentally different in kind, from those of nonhuman creatures. Philosophically, we utilize the power-object model of division and Aristotle’s categorization of knowledge to express the difference in kind between human beings and other animals. These responses allow us to set aside each major objection
Extension of the fuzzy integral for general fuzzy set-valued information
The fuzzy integral (FI) is an extremely flexible aggregation operator. It is used in numerous applications, such as image processing, multicriteria decision making, skeletal age-at-death estimation, and multisource (e.g., feature, algorithm, sensor, and confidence) fusion. To date, a few works have appeared on the topic of generalizing Sugeno's original real-valued integrand and fuzzy measure (FM) for the case of higher order uncertain information (both integrand and measure). For the most part, these extensions are motivated by, and are consistent with, Zadeh's extension principle (EP). Namely, existing extensions focus on fuzzy number (FN), i.e., convex and normal fuzzy set- (FS) valued integrands. Herein, we put forth a new definition, called the generalized FI (gFI), and efficient algorithm for calculation for FS-valued integrands. In addition, we compare the gFI, numerically and theoretically, with our non-EP-based FI extension called the nondirect FI (NDFI). Examples are investigated in the areas of skeletal age-at-death estimation in forensic anthropology and multisource fusion. These applications help demonstrate the need and benefit of the proposed work. In particular, we show there is not one supreme technique. Instead, multiple extensions are of benefit in different contexts and applications
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