4,632 research outputs found
Chain Homotopies for Object Topological Representations
This paper presents a set of tools to compute topological information of
simplicial complexes, tools that are applicable to extract topological
information from digital pictures. A simplicial complex is encoded in a
(non-unique) algebraic-topological format called AM-model. An AM-model for a
given object K is determined by a concrete chain homotopy and it provides, in
particular, integer (co)homology generators of K and representative (co)cycles
of these generators. An algorithm for computing an AM-model and the
cohomological invariant HB1 (derived from the rank of the cohomology ring) with
integer coefficients for a finite simplicial complex in any dimension is
designed here. A concept of generators which are "nicely" representative cycles
is also presented. Moreover, we extend the definition of AM-models to 3D binary
digital images and we design algorithms to update the AM-model information
after voxel set operations (union, intersection, difference and inverse)
Using membrane computing for obtaining homology groups of binary 2D digital images
Membrane Computing is a new paradigm inspired from cellular communication. Until now, P systems have been used in research areas like modeling chemical process, several ecosystems, etc. In this paper, we apply P systems to Computational Topology within the context of the Digital Image. We work with a variant of P systems called tissue-like P systems to calculate in a general maximally parallel manner the homology groups of 2D images. In fact, homology computation for binary pixel-based 2D digital images can be reduced to connected component labeling of white and black regions. Finally, we use a software called Tissue Simulator to show with some examples how these systems wor
Observations of the first electromagnetic counterpart to a gravitational wave source by the TOROS collaboration
We present the results of prompt optical follow-up of the electromagnetic counterpart of GW170817 by the Transient Optical Robotic Observatory of the South Collaboration (TOROS). We detected highly significant dimming in the light curves of the counterpart over the course of only 80 minutes of observations obtained âŒ35 hr after the trigger with the T80-South telescope. A second epoch of observations, obtained âŒ59 hr after the event with the EABA 1.5m telescope, confirms the fast fading nature of the transient. The observed colors of the counterpart suggest that this event was a blue kilonova relatively free of lanthanides
Tuning Proton Conductivity Properties of Lanthanide Amino-Sulfophosphonates-Loaded Nafion Composite Membranes
Polymer-based electrolytes in proton exchange membrane fuel cells (PEMFCs) utilize acidic groups as proton carriers and hydrogen bonding networks as proton-conducting pathways to facilitate proton transport. Crystalline acid-functionalized metal phosphonates are potential proton conductors while maintaining a high hydration degree below 100 °C. This property may be combined with Nafion-like polymers which tend to dehydrate at the operating conditions of PEMFCs [1,2]. In this work, preliminary results of the preparation of lanthanide amino-sulfophosphonates-loaded Nafion composites membranes and the corresponding electrical properties are reported. Synthesis conditions of lanthanide derivatives were optimized following a hightrough-put screening at 140 °C. Their crystal structures, solved from synchrotron X-ray powder diffraction data, corresponds to layered frameworks where the acidic groups, -CPO3H or -SO3H, point toward the interlamellar region interacting by H-bond with the lattice water. The composites were prepared by mixing the metal phosphonates with Nafion solution at different loadings. The membranes were characterized by SEM, XRD and FT-IR. A study of the proton conductivity as a function of the composite membranes was carried out at 90 °C and 95% RH. Referencias [1] Y. Gao, R. Broersen, W. Hageman, N. Yan, M. C. Mittelmeijer-Hazeleger, G. Rothenberg, S. Tanase. J. Mater. Chem. A, 2015, 3, 22347â22352. [2] A. Cabeza, P. Olivera-Pastor, R. M. P. Colodrero. Tailored Organic-Inorganic Materials, Brunet, E., ColĂłn, J.L., Clearfield, A., Eds.; John Wiley & Sons, Inc. 2015; Ch. 4, 137â191.Universidad de MĂĄlaga. Campus de Excelencia Internacional AndalucĂa Tech
Physiological Benefits and Performance of Sea Water Ingestion for Athletes in Endurance Events: A Systematic Review
In different endurance events, athletes have limited access to fluid intake, such as ultraendurance
running. For this reason, it is necessary to establish an adequate hydration strategy for
this type of long-duration sporting event. Indeed, it seems that the intake of seawater is a suitable
hydration alternative to improve post-exercise recovery in this type of endurance event. This seawater
is characterized by being a deep natural mineral water of moderate mineralization, which is usually
extracted from a depth of about 700 m. Therefore, the aim of this systematic review is to evaluate the
efficacy of seawater consumption in both performance and post-exercise recovery in long-duration
sport events. A systematic and comprehensive literature search was performed in PubMed, Scopus,
andWeb of Science in September 2022. Initially, 8 out of 558 articles met the inclusion criteria. Among
these eight studies, six were randomized clinical trials, and two were observational studies (one
cross-sectional and one prospective study in well-conditioned student athletes). The results showed
that deep sea water consumption accelerated the recovery of aerobic capacity and leg muscle capacity
on running performance. In addition, the lactate production after the running exercise in seawater
was significantly lower than in pure water. In conclusion, the present review demonstrates that
seawater consumption could significantly improve the capacity of recovery after exercise."Fundacion Ramon Areces", Madrid, SpainConsejo Nacional de Ciencia y Tecnologia (CONACyT) 218582/47197
Slit Observations and Empirical Calculations for HII Regions
When analysing HII regions, a possible source of systematic error on
empirically derived physical quantities is the limited size of the slit used
for the observations. A grid of photoionization models was built through the
Aangaba code varying the ionizing radiation spectrum emitted by a stellar
cluster, as well as the gas abundance. The calculated line surface brightness
was then used to simulate slit observations and to derive empirical parameters
using the usual methods described in the literature. Depending on the fraction
of the object covered by the slit, the parameters can be different from those
obtained from observations of the whole object, an effect that is mainly
dependent on the age of the ionizing stellar cluster. The low-ionization
forbidden lines are more sensitive to the size of the area covered by the slit
than the high-ionization forbidden lines or recombination lines. Regarding the
temperature indicator T[OIII], the slit effects are small since this
temperature is derived from [OIII] lines. On the other hand, for the abundance
indicator R23, which depends also on the [OII] line, the slit effect is
slightly higher. Therefore, the systematic error due to slit observations on
the O abundance is low, being usually less than 10%, except for HII regions
powered by stellar clusters with a relative low number of ionizing photons
between 13.6 and 54.4 eV, which create a smaller O++ emitting volume. In this
case, the systematic error on the empirical O abundance deduced from slit
observations is more than 10% when the covered area is less than 50%.Comment: To be published in MNRAS, accepted in 09/09/2005, 17 pages and 6
figure
A diphenyldiselenide derivative induces autophagy via JNK in HTB-54 lung cancer cells
Symmetric aromatic diselenides are potential anticancer agents with strong cytotoxic activity. In this study, the in vitro anticancer activities of a novel series of diarylseleno derivatives from the diphenyldiselenide (DPDS) scaffold were evaluated. Most of the compounds exhibited high efficacy for inducing cytotoxicity against different human cancer cell lines. DPDS 2, the compound with the lowest mean GI50 value, induced both caspase-dependent apoptosis and arrest at the G0/G1 phase in acute lymphoblastic leucemia CCRF-CEM cells. Consistent with this, PARP cleavage; enhanced caspase-2, -3, -8 and -9 activity; reduced CDK4 expression and increased levels of p53 were detected in these cells upon DPDS 2 treatment. Mutated p53 expressed in CCRF-CEM cells retains its transactivating activity. Therefore, increased levels of p21CIP1 and BAX proteins were also detected. On the other hand, DPDS 6, the compound with the highest selectivity index for cancer cells, resulted in G2/M cell cycle arrest and caspase-independent cell death in p53 deficient HTB-54 lung cancer cells. Autophagy inhibitors 3-methyladenine, wortmannin and chloroquine inhibited DPDS 6-induced cell death. Consistent with autophagy, increased LC3-II and decreased SQSTM1/p62 levels were detected in HTB-54 cells in response to DPDS 6. Induction of JNK phosphorylation and a reduction in phospho-p38 MAPK were also detected. Moreover, the JNK inhibitor SP600125-protected HTB-54 cells from DPDS 6-induced cell death indicating that JNK activation is involved in DPDS 6-induced autophagy. These results highlight the anticancer effects of these derivatives and warrant future studies examining their clinical potential
Delta rho pi interaction leading to N* and Delta* resonances
We have performed a calculation for the three body system
by using the fixed center approximation to Faddeev equations, taking the
interaction between and , and, and and
from the chiral unitary approach. We find several peaks in the modulus
squared of the three-body scattering amplitude, indicating the existence of
resonances, which can be associated to known and and baryon states.Comment: Presented at the 21st European Conference on Few-Body Problems in
Physics, Salamanca, Spain, 30 August - 3 September 201
Homological computation using spanning trees
We introduce here a new F2 homology computation algorithm based on a generalization of the spanning tree technique on a finite 3-dimensional cell complex K embedded in â3. We demonstrate that the complexity of this algorithm is linear in the number of cells. In fact, this process computes an algebraic map Ï over K, called homology gradient vector field (HGVF), from which it is possible to infer in a straightforward manner homological information like Euler characteristic, relative homology groups, representative cycles for homology generators, topological skeletons, Reeb graphs, cohomology algebra, higher (co)homology operations, etc. This process can be generalized to others coefficients, including the integers, and to higher dimension
Multi-band high resolution spectroscopy rules out the hot Jupiter BD+20 1790b - First data from the GIARPS Commissioning
Context. Stellar activity is currently challenging the detection of young
planets via the radial velocity (RV) technique. Aims. We attempt to
definitively discriminate the nature of the RV variations for the young active
K5 star BD+20 1790, for which visible (VIS) RV measurements show divergent
results on the existence of a substellar companion. Methods. We compare VIS
data with high precision RVs in the near infrared (NIR) range by using the
GIANO - B and IGRINS spectrographs. In addition, we present for the first time
simultaneous VIS-NIR observations obtained with GIARPS (GIANO - B and HARPS -
N) at Telescopio Nazionale Galileo (TNG). Orbital RVs are achromatic, so the RV
amplitude does not change at different wavelengths, while stellar activity
induces wavelength-dependent RV variations, which are significantly reduced in
the NIR range with respect to the VIS. Results. The NIR radial velocity
measurements from GIANO - B and IGRINS show an average amplitude of about one
quarter with respect to previously published VIS data, as expected when the RV
jitter is due to stellar activity. Coeval multi-band photometry surprisingly
shows larger amplitudes in the NIR range, explainable with a mixture of cool
and hot spots in the same active region. Conclusions. In this work, the claimed
massive planet around BD+20 1790 is ruled out by our data. We exploited the
crucial role of multi- wavelength spectroscopy when observing young active
stars: thanks to facilities like GIARPS that provide simultaneous observations,
this method can reach its maximum potential.Comment: 12 pages, 7 figure
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