33,620 research outputs found
What explains the invading success of the aquatic mud snail Potamopyrgus antipodarum (Hydrobiidae, Mollusca)?
The spread of non-native species is one of the most harmful and least reversible disturbances in ecosystems. Species have to overcome several filters to become a pest (transport, establishment, spread and impact). Few studies have checked the traits that confer ability to overcome these steps in the same species. The aim of the present study is to review the available information on the life-history and ecological traits of the mud snail, Potamopyrgus antipodarum Gray (Hydrobiidae, Mollusca), native from New Zealand, in order to explain its invasive success at different aquatic ecosystems around the world. A wide tolerance range to physico-chemical factors has been found to be a key trait for successful transport. A high competitive ability at early stages of succession can explains its establishment success in human-altered ecosystems. A high reproduction rate, high capacity for active and passive dispersal, and the escape from native predators and parasites explains its spread success. The high reproduction and the ability to monopolize invertebrate secondary production explain its high impact in the invaded ecosystems. However, further research is needed to understand how other factors, such as population density or the degree of human perturbation can modify the invasive success of this aquatic snai
Cooperation between expert knowledge and data mining discovered knowledge: Lessons learned
Expert systems are built from knowledge traditionally elicited from the human expert. It is precisely knowledge elicitation from the expert that is the bottleneck in expert system construction. On the other hand, a data mining system, which automatically extracts knowledge, needs expert guidance on the successive decisions to be made in each of the system phases. In this context, expert knowledge and data mining discovered knowledge can cooperate, maximizing their individual capabilities: data mining discovered knowledge can be used as a complementary source of knowledge for the expert system, whereas expert knowledge can be used to guide the data mining process. This article summarizes different examples of systems where there is cooperation between expert knowledge and data mining discovered knowledge and reports our experience of such cooperation gathered from a medical diagnosis project called Intelligent Interpretation of Isokinetics Data, which we developed. From that experience, a series of lessons were learned throughout project development. Some of these lessons are generally applicable and others pertain exclusively to certain project types
Generalized uncertainty principle impact onto the black holes information flux and the sparsity of Hawking radiation
We investigate the generalized uncertainty principle (GUP) corrections to the
entropy content and the information flux of black holes, as well as the
corrections to the sparsity of the Hawking radiation at the late stages of
evaporation. We find that due to these quantum gravity motivated corrections,
the entropy flow per particle reduces its value on the approach to the Planck
scale due to a better accuracy in counting the number of microstates. We also
show that the radiation flow is no longer sparse when the mass of a black hole
approaches Planck mass which is not the case for non-GUP calculations.Comment: 6 pages, 2 figures, typos corrected, published in Phys. Rev.
Minimal length and the flow of entropy from black holes
The existence of a minimal length, predicted by different theories of quantum
gravity, can be phenomenologically described in terms of a generalized
uncertainty principle. We consider the impact of this quantum gravity motivated
effect onto the information budget of a black hole and the sparsity of Hawking
radiation during the black hole evaporation process. We show that the
information is not transmitted at the same rate during the final stages of the
evaporation and that the Hawking radiation is not sparse anymore when the black
hole approaches the Planck mass.Comment: Awarded Honorable Mention in the 2018 Gravity Research Foundation
Essay Competitio
The silicate absorption profile in the ISM towards the heavily obscured nucleus of NGC 4418
The 9.7-micron silicate absorption profile in the interstellar medium
provides important information on the physical and chemical composition of
interstellar dust grains. Measurements in the Milky Way have shown that the
profile in the diffuse interstellar medium is very similar to the amorphous
silicate profiles found in circumstellar dust shells around late M stars, and
narrower than the silicate profile in denser star-forming regions. Here, we
investigate the silicate absorption profile towards the very heavily obscured
nucleus of NGC 4418, the galaxy with the deepest known silicate absorption
feature, and compare it to the profiles seen in the Milky Way. Comparison
between the 8-13 micron spectrum obtained with TReCS on Gemini and the larger
aperture spectrum obtained from the Spitzer archive indicates that the former
isolates the nuclear emission, while Spitzer detects low surface brightness
circumnuclear diffuse emission in addition. The silicate absorption profile
towards the nucleus is very similar to that in the diffuse ISM in the Milky Way
with no evidence of spectral structure from crystalline silicates or silicon
carbide grains.Comment: 7 Pages, 3 figures. MNRAS in pres
Scalable arrays of micro-Penning traps for quantum computing and simulation
We propose the use of 2-dimensional Penning trap arrays as a scalable
platform for quantum simulation and quantum computing with trapped atomic ions.
This approach involves placing arrays of micro-structured electrodes defining
static electric quadrupole sites in a magnetic field, with single ions trapped
at each site and coupled to neighbors via the Coulomb interaction. We solve for
the normal modes of ion motion in such arrays, and derive a generalized
multi-ion invariance theorem for stable motion even in the presence of trap
imperfections. We use these techniques to investigate the feasibility of
quantum simulation and quantum computation in fixed ion lattices. In
homogeneous arrays, we show that sufficiently dense arrays are achievable, with
axial, magnetron and cyclotron motions exhibiting inter-ion dipolar coupling
with rates significantly higher than expected decoherence. With the addition of
laser fields these can realize tunable-range interacting spin Hamiltonians. We
also show how local control of potentials allows isolation of small numbers of
ions in a fixed array and can be used to implement high fidelity gates. The use
of static trapping fields means that our approach is not limited by power
requirements as system size increases, removing a major challenge for scaling
which is present in standard radio-frequency traps. Thus the architecture and
methods provided here appear to open a path for trapped-ion quantum computing
to reach fault-tolerant scale devices.Comment: 21 pages, 10 figures Changes include adding section IX
(Implementation Example) and substantially rewriting section X (Scaling
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