11,383 research outputs found
Control of synchronization regimes in networks of mobile interacting agents
We investigate synchronization in a population of mobile pulse-coupled agents with a view towards
implementations in swarm robotics systems and mobile sensor networks. Previous theoretical
approaches dealt with range and nearest neighbor interactions. In the latter case, a synchronization-hindering
regime for intermediate agent mobility was found. In the present work, we investigate
the robustness of this intermediate regime under practical scenarios. We show that synchronization
in the intermediate regime can be predicted by means of a suitable metric of the phase response
curve. Furthermore, we study more realistic K-nearest neighbors and cone of vision interactions,
showing that it is possible to control the extent of the synchronization-hindering region by appropriately
tuning the size of the neighborhood. To assess the effect of noise, we analyze the
propagation of perturbations over the network and draw an analogy between the response in the
hindering regime and stable chaos. Our findings reveal the conditions for the control of clock or
activity synchronization of agents with intermediate mobility. In addition, the emergence of the
intermediate regime is validated experimentally using a swarm of physical robots interacting with
cone of vision interactions
Discovery of a wide companion near the deuterium burning mass limit in the Upper Scorpius association
We present the discovery of a companion near the deuterium burning mass limit
located at a very wide distance, at an angular separation of 4.6+/-0.1 arcsec
(projected distance of ~ 670 AU) from UScoCTIO108, a brown dwarf of the very
young Upper Scorpius association. Optical and near-infrared photometry and
spectroscopy confirm the cool nature of both objects, with spectral types of M7
and M9.5, respectively, and that they are bona fide members of the association,
showing low gravity and features of youth. Their masses, estimated from the
comparison of their bolometric luminosities and theoretical models for the age
range of the association, are 60+/-20 and 14^{+2}_{-8} MJup, respectively. The
existence of this object around a brown dwarf at this wide orbit suggests that
the companion is unlikely to have formed in a disk based on current planet
formation models. Because this system is rather weakly bound, they did not
probably form through dynamical ejection of stellar embryos.Comment: 10 pages, including 4 figures and 2 table
Computing the Singularities of Rational Surfaces
Given a rational projective parametrization \cP(\ttt,\sss,\vvv) of a
rational projective surface \cS we present an algorithm such that, with the
exception of a finite set (maybe empty) \cB of projective base points of
\cP, decomposes the projective parameter plane as \projdos\setminus
\cB=\cup_{k=1}^{\ell} \cSm_k such that if (\ttt_0:\sss_0:\vvv_0)\in \cSm_k
then \cP(\ttt_0,\sss_0,\vvv_0) is a point of \cS of multiplicity .Comment: In this new version, we only have changed the thanks. In particular,
we have written: This work was developed, and partially supported, under the
research project MTM2008-04699-C03-01 "Variedades param\'etricas: algoritmos
y aplicaciones", Ministerio de Ciencia e Innovaci\'on, Spain and by "Fondos
Europeos de Desarrollo Regional" of the European Unio
High spatial resolution and high contrast optical speckle imaging with FASTCAM at the ORM
In this paper, we present an original observational approach, which combines,
for the first time, traditional speckle imaging with image post-processing to
obtain in the optical domain diffraction-limited images with high contrast
(1e-5) within 0.5 to 2 arcseconds around a bright star. The post-processing
step is based on wavelet filtering an has analogy with edge enhancement and
high-pass filtering. Our I-band on-sky results with the 2.5-m Nordic Telescope
(NOT) and the lucky imaging instrument FASTCAM show that we are able to detect
L-type brown dwarf companions around a solar-type star with a contrast DI~12 at
2" and with no use of any coronographic capability, which greatly simplifies
the instrumental and hardware approach. This object has been detected from the
ground in J and H bands so far only with AO-assisted 8-10 m class telescopes
(Gemini, Keck), although more recently detected with small-class telescopes in
the K band. Discussing the advantage and disadvantage of the optical regime for
the detection of faint intrinsic fluxes close to bright stars, we develop some
perspectives for other fields, including the study of dense cores in globular
clusters. To the best of our knowledge this is the first time that high
contrast considerations are included in optical speckle imaging approach.Comment: Proceedings of SPIE conference - Ground-based and Airborne
Instrumentation for Astronomy III (Conference 7735), San Diego 201
LAGOVirtual: A Collaborative Environment for the Large Aperture GRB Observatory
We present the LAGOVirtual Project: an ongoing project to develop platform to
collaborate in the Large Aperture GRB Observatory (LAGO). This continental-wide
observatory is devised to detect high energy (around 100 GeV) component of
Gamma Ray Bursts, by using the single particle technique in arrays of Water
Cherenkov Detectors (WCD) at high mountain sites (Chacaltaya, Bolivia, 5300 m
a.s.l., Pico Espejo, Venezuela, 4750 m a.s.l., Sierra Negra, Mexico, 4650 m
a.s.l). This platform will allow LAGO collaboration to share data, and computer
resources through its different sites. This environment has the possibility to
generate synthetic data by simulating the showers through AIRES application and
to store/preserve distributed data files collected by the WCD at the LAGO
sites. The present article concerns the implementation of a prototype of
LAGO-DR adapting DSpace, with a hierarchical structure (i.e. country,
institution, followed by collections that contain the metadata and data files),
for the captured/simulated data. This structure was generated by using the
community, sub-community, collection, item model; available at the DSpace
software. Each member institution-country of the project has the appropriate
permissions on the system to publish information (descriptive metadata and
associated data files). The platform can also associate multiple files to each
item of data (data from the instruments, graphics, postprocessed-data, etc.).Comment: Second EELA-2 Conference Choroni, Venezuela, November 25th to 27th
200
Comparison of Physiological Responses and Perceived Respiratory Resistance Among Mask Usage During Exercise
Since the beginning of the COVID-19 pandemic, the use of a face mask in public is recommended when social distancing cannot be maintained to decrease the spread of the virus with many fitness facilities requiring their patrons to wear a face mask during exercise. The physiological response of wearing a face mask during exercise is relatively unknown and is speculated among the media resulting in contradicting messages conveyed to the public PURPOSE: The purpose of this study was to determine if a face mask influenced performance (time to exhaustion), physiological responses (heart rate, oxyhemoglobin saturation and temperature) and subjective measurements such as dyspnea, perceived respiratory resistance, and rating of perceived exertion (RPE) during exercise. METHODS: Fifteen healthy males (n =8) and females (n=7) completed three graded exercise treadmill tests with (1) a surgical face mask, (2) a cloth face mask, and (3) no mask randomly with at least 48hrs apart. Heart rate (HR), oxyhemoglobin saturation (SpO2), temperature, RPE, dyspnea, was measured throughout exercise. Participants rated their perceived respiratory resistance for each condition at rest, beginning of exercise, and at fatigue using a 100 mm visual analog scale. RESULTS: Significant differences (p \u3c 0.05) were observed in perceived respiratory resistance between no mask and both surgical and cloth conditions at rest (1.55 ± 2.34mm; 6.33 ± 6.11mm; 9.67 ± 10.77mm respectively) and at the beginning of exercise (5.93 ± 6.64mm; 15.47 ± 12.56mm; 21.07± 15.04mm respectively). During stage 3 of the exercise test, the no mask condition had a significantly lower RPE compared to the cloth mask condition (13.22 ± 2.14;14.60 ± 2.13 respectively). Time to exhaustion was similar for all conditions (mask: 11:51 ± 2:31min; cloth: 11:16 ± 2:24min; surgical: 11:32 ± 2:23min). At all times points, there was no significant (p \u3e 0.05) difference between the conditions for HR, SpO2, temperature, and dyspnea. CONCLUSION: Wearing either a surgical or cloth face mask is safe during exercise in healthy adults and has no effect on HR, SpO2, or body temperature. It appears that wearing a face mask may have a minor influence on subjective measurements such as perceived respiratory resistance or RPE during exercise
Phytoremediation of Heavy Metal Contaminated Wastes From Small-Scale Gold Mining Using Pityrogramma calomelanos
In this study, viability of employing the waste treatment technique for industrial application was conducted by setting up a phytoremediation protocol for field application where heavy metal (Arsenic and Copper) contaminated adsorbents, i.e. coco peat and nanofiber membrane, used for the treatment of wastewater were also included. An arsenic hyperaccumulator, Pityrogramma calomelanos was used for the treatment of mine wastes-tailings, coco peat and nanofiber membrane. Phytoremediation procedure was established by investigating planting parameters namely ; plot height - (9 cm and 15 cm) and planting distance- (15 cm and 20 cm) for a period of five months. Translocation factor and % uptake of As and Cu by ferns were measured. According to the results, % uptake of As and Cu by P. Calomelanos was 0.16 % and 0.01 % and translocation factor of As and Cu was 6.78 and 0.04, respectively. Plant growth factors (root length, frond height and dry weight) in tailings mixture plant boxes and control soil were also determined. Accordingly, P. calomelanos grew well in tailings mixture without the symptom of phytotoxicity. Therefore, P. calomelanos can be used for the phytoremediation of the said heavy metal contaminated mine wastes. Based on this study, 15 cm plot height and 20 cm plant distance were suitable for field experiment although long term research data is required. The overall protocol for the treatment of mine wastes as field experiment was proposed based on the results
Firefly-Inspired Synchronization in Swarms of Mobile Agents
Recently, there has been growing interest in the synchronization of mobile pulse-coupled oscillators. We build on the work by Prignano et al. (Phys. Rev. Lett. 110, 114101) and show that agents that interact exclusively with others in their cone of vision can exhibit different synchronization regimes. Depending on their speed, synchronization emerges as a slow process through spreading of the local coherence, as a fast process where global synchronization dominates, or it is inhibited for a range of intermediate speeds. In addition, we show that, not only the speed of the agents, but also their angle and range of interaction can tune the appearance of this intermediate regime
Modular Hydraulic Propulsion: A Robot that Moves by Routing Fluid Through Itself
This paper introduces the concept of Modular
Hydraulic Propulsion, in which a modular robot that operates
in a fluid environment moves by routing the fluid through
itself. The robot’s modules represent sections of a hydraulics
network. Each module can move fluid between any of its
faces. The modules (network sections) can be rearranged
into arbitrary topologies. We propose a decentralized motion
controller, which does not require modules to communicate,
compute, nor store information during run-time. We use 3-D
simulations to compare the performance of this controller to
that of a centralized controller with full knowledge of the task.
We also detail the design and fabrication of six 2-D prototype
modules, which float in a water tank. Results of systematic
experiments show that the decentralized controller, despite its
simplicity, reliably steers modular robots towards a light source.
Modular Hydraulic Propulsion could offer new solutions to
problems requiring reconfigurable systems to move precisely
in 3-D, such as inspection of pipes, vascular systems or other
confined spaces
Characterization of a putative grapevine Zn transporter, VvZIP3, suggests its involvement in early reproductive development in Vitis vinifera L
Gonzalez, E (reprint author), Univ Talca, Inst Biol Vegetal & Biotecnol, Talca, Chile.Background: Zinc (Zn) deficiency is one of the most widespread mineral nutritional problems that affect normal development in plants. Because Zn cannot passively diffuse across cell membranes, it must be transported into intracellular compartments for all biological processes where Zn is required. Several members of the Zinc-regulated transporters, Iron-regulated transporter-like Protein (ZIP) gene family have been characterized in plants, and have shown to be involved in metal uptake and transport. This study describes the first putative Zn transporter in grapevine. Unravelling its function may explain an important symptom of Zn deficiency in grapevines, which is the production of clusters with fewer and usually smaller berries than normal.
Results: We identified and characterized a putative Zn transporter from berries of Vitis vinifera L., named VvZIP3. Compared to other members of the ZIP family identified in the Vitis vinifera L. genome, VvZIP3 is mainly expressed in reproductive tissue - specifically in developing flowers - which correlates with the high Zn accumulation in these organs. Contrary to this, the low expression of VvZIP3 in parthenocarpic berries shows a relationship with the lower Zn accumulation in this tissue than in normal seeded berries where its expression is induced by Zn. The predicted protein sequence indicates strong similarity with several members of the ZIP family from Arabidopsis thaliana and other species. Moreover, VvZIP3 complemented the growth defect of a yeast Zn-uptake mutant, ZHY3, and is localized in the plasma membrane of plant cells, suggesting that VvZIP3 has the function of a Zn uptake transporter.
Conclusions: Our results suggest that VvZIP3 encodes a putative plasma membrane Zn transporter protein member of the ZIP gene family that might play a role in Zn uptake and distribution during the early reproductive development in Vitis vinifera L., indicating that the availability of this micronutrient may be relevant for reproductive development
- …