3,973 research outputs found
Lower bounds on concurrence and separability conditions
We obtain analytical lower bounds on the concurrence of bipartite quantum
systems in arbitrary dimensions related to the violation of separability
conditions based on local uncertainty relations and on the Bloch representation
of density matrices. We also illustrate how these results complement and
improve those recently derived [K. Chen, S. Albeverio, and S.-M. Fei, Phys.
Rev. Lett. 95, 040504 (2005)] by considering the Peres-Horodecki and the
computable cross norm or realignment criteria.Comment: 5 pages, 1 figure; minor changes, references added; final version:
minor correction in proof of lemma 1, scope of theorem 2 clarified, to appear
in PRA; mistake in proof of lemma 1 of published version corrected, results
unchange
Searching for Elko dark matter spinors at the CERN LHC
The aim of this work is to explore the possibility to discover a fermionic
field with mass dimension one, the Elko field, in the Large Hadron Collider
(LHC). Due to its mass dimension, an Elko can only interact either with
Standard Model (SM) spinors and gauge fields at 1-loop order or at tree level
through a quartic interaction with the Higgs field. In this Higgs portal
scenario, the Elko is a viable candidate to a dark matter constituent which has
been shown to be compatible with relic abundance measurements from WMAP and
direct dark matter--nucleon searches. We propose a search strategy for this
dark matter candidate in the channel at
the TeV LHC. We show the LHC potential to discover the Elko
considering a triple Higgs-Elko coupling as small as after 1
pb of integrated luminosity. Some phenomenological consequences of this
new particle and its collider signatures are also discussed.Comment: 7 pages, 3 figure
Instantaneous cell migration velocity may be ill-defined
Cell crawling is critical to biological development, homeostasis and disease.
In many cases, cell trajectories are quasi-random-walk. In vitro assays on flat
surfaces often described such quasi-random-walk cell trajectories as
approximations to a solution of a Langevin process. However, experiments show
quasi-diffusive behavior at small timescales, indicating that instantaneous
velocity and velocity autocorrelations are not well-defined. We propose to
characterize mean-squared cell displacement using a modified F\"urth equation
with three temporal and spatial regimes: short- and long-time/range diffusion
and intermediate time/range ballistic motion. This analysis collapses
mean-squared displacements of previously published experimental data onto a
single-parameter family of curves, allowing direct comparison between movement
in different cell types, and between experiments and numerical simulations. Our
method also show that robust cell-motility quantification requires an
experiment with a maximum interval between images of a few percent of the
cell-motion persistence time or less, and a duration of a few
orders-of-magnitude longer than the cell-motion persistence time or more.Comment: 5 pages, plus Supplemental materia
Quantifying responses of dung beetles to fire disturbance in tropical forests:the importance of trapping method and seasonality
Understanding how biodiversity responds to environmental changes is essential to provide the evidence-base that underpins conservation initiatives. The present study provides a standardized comparison between unbaited flight intercept traps (FIT) and baited pitfall traps (BPT) for sampling dung beetles. We examine the effectiveness of the two to assess fire disturbance effects and how trap performance is affected by seasonality. The study was carried out in a transitional forest between Cerrado (Brazilian Savanna) and Amazon Forest. Dung beetles were collected during one wet and one dry sampling season. The two methods sampled different portions of the local beetle assemblage. Both FIT and BPT were sensitive to fire disturbance during the wet season, but only BPT detected community differences during the dry season. Both traps showed similar correlation with environmental factors. Our results indicate that seasonality had a stronger effect than trap type, with BPT more effective and robust under low population numbers, and FIT more sensitive to fine scale heterogeneity patterns. This study shows the strengths and weaknesses of two commonly used methodologies for sampling dung beetles in tropical forests, as well as highlighting the importance of seasonality in shaping the results obtained by both sampling strategies
A Dataset of Fact-Checked Images Shared on WhatsApp During the Brazilian and Indian Elections
Recently, messaging applications, such as WhatsApp, have been reportedly
abused by misinformation campaigns, especially in Brazil and India. A notable
form of abuse in WhatsApp relies on several manipulated images and memes
containing all kinds of fake stories. In this work, we performed an extensive
data collection from a large set of WhatsApp publicly accessible groups and
fact-checking agency websites. This paper opens a novel dataset to the research
community containing fact-checked fake images shared through WhatsApp for two
distinct scenarios known for the spread of fake news on the platform: the 2018
Brazilian elections and the 2019 Indian elections.Comment: 7 pages. This is a preprint version of an accepted paper on ICWSM'20.
Please, consider to cite the conference version instead of this on
Breaking bony bridges by physeal distraction
Physeal distraction for breaking bony bridges and the late treatment of long bone deformities in children near maturity, has been used in our Department since June, 1983. In all cases (4 bones in 3 patients) a deformity was present at the extremity of a long bone due to a bony bridge caused by a previous injury to the growth cartilage. The results were excellent and in our opinion there are advantages over other methods. The operation itself is not extensive and very little damage is done. There is no need for internal fixation or bone grafts. It is possible to obtain lengthening and to adjust the angular correction during treatment. We conclude that it is possible to correct angular deformities and bone shortening due to bony bridges by physeal distraction without the need for resection of the bony bridge. At present we recommend this method in children near skeletal maturity, especially in those cases with bone shortening
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