2,875 research outputs found
CO observations and investigation of triggered star formation towards N10 infrared bubble and surroundings
We studied the environment of the dust bubble N10 in molecular emission.
Infrared bubbles, first detected by the GLIMPSE survey at 8.0 m, are ideal
regions to investigate the effect of the expansion of the HII region on its
surroundings eventual triggered star formation at its borders. In this work, we
present a multi-wavelength study of N10. This bubble is especially interesting
as infrared studies of the young stellar content suggest a scenario of ongoing
star formation, possibly triggered, on the edge of the HII region. We carried
out observations of CO(1-0) and CO(1-0) emission at PMO 13.7-m
towards N10. We also analyzed the IR and sub-mm emission on this region and
compare those different tracers to obtain a detailed view of the interaction
between the expanding HII region and the molecular gas. We also estimated the
parameters of the denser cold dust condensation and of the ionized gas inside
the shell. Bright CO emission was detected and two molecular clumps were
identified, from which we have derived physical parameters. We also estimate
the parameters for the densest cold dust condensation and for the ionized gas
inside the shell. The comparison between the dynamical age of this region and
the fragmentation time scale favors the "Radiation-Driven Implosion" mechanism
of star formation. N10 reveals to be specially interesting case with gas
structures in a narrow frontier between HII region and surrounding molecular
material, and with a range of ages of YSOs situated in region indicating
triggered star formation.Comment: Version 2 - Submmited to ApJ (under review
Evolution of the geomagnetic daily variation at Tatuoca, Brazil, from 1957 to 2019: a transition from Sq to EEJ
The magnetic equator in the Brazilian region has moved over 1,100 km northward since 1957, passing the geomagnetic observatory Tatuoca (TTB), in northern Brazil, around 2013. We recovered and processed TTB hourly mean values of the geomagnetic field horizontal (H) component from 1957 until 2019, allowing the investigation of longâterm changes in the daily variation due to the influence of secular variation, solar activity, season, and lunar phase. The H dayâtoâday variability and the occurrence of the counter electrojet at TTB were also investigated. Until the 1990s, ionospheric solar quiet currents dominated the quietâtime daily variation at TTB. After 2000, the magnitude of the daily variation became appreciably greater due to the equatorial electrojet (EEJ) contribution. The H seasonal and dayâtoâday variability increased as the magnetic equator approached, but their amplitudes normalized to the average daily variation remained at similar levels. Meanwhile, the amplitude of the lunar variation, normalized in the same way, increased from 5% to 12%. Within the EEJ region, the occurrence rate of the morning counter electrojet (MCEJ) increased with proximity to the magnetic equator, while the afternoon counter electrojet (ACEJ) did not. EEJ currents derived from CHAMP and Swarm satellite data revealed that the MCEJ rate varies with magnetic latitude within the EEJ region while the ACEJ rate is largely constant. Simulations with the ThermosphereâIonosphereâElectrodynamics General Circulation Model based on different geomagnetic main field configurations suggest that longâterm changes in the geomagnetic daily variation at TTB can be attributed to the main field secular variation
Interfacial motion in flexo- and order-electric switching between nematic filled states
We consider a nematic liquid crystal, in coexistence with its isotropic
phase, in contact with a substrate patterned with rectangular grooves. In such
a system, the nematic phase may fill the grooves without the occurrence of
complete wetting. There may exist multiple (meta)stable filled states, each
characterised by the type of distortion (bend or splay) in each corner of the
groove and by the shape of the nematic-isotropic interface, and additionally
the plateaux that separate the grooves may be either dry or wet with a thin
layer of nematic. Using numerical simulations, we analyse the dynamical
response of the system to an externally- applied electric field, with the aim
of identifying switching transitions between these filled states. We find that
order-electric coupling between the fluid and the field provides a means of
switching between states where the plateaux between grooves are dry and states
where they are wet by a nematic layer, without affecting the configuration of
the nematic within the groove. We find that flexoelectric coupling may change
the nematic texture in the groove, provided that the flexoelectric coupling
differentiates between the types of distortion at the corners of the substrate.
We identify intermediate stages of the transitions, and the role played by the
motion of the nematic-isotropic interface. We determine quantitatively the
field magnitudes and orientations required to effect each type of transition.Comment: 14 pages, 12 fig
Solving the Shortest Vector Problem in Lattices Faster Using Quantum Search
By applying Grover's quantum search algorithm to the lattice algorithms of
Micciancio and Voulgaris, Nguyen and Vidick, Wang et al., and Pujol and
Stehl\'{e}, we obtain improved asymptotic quantum results for solving the
shortest vector problem. With quantum computers we can provably find a shortest
vector in time , improving upon the classical time
complexity of of Pujol and Stehl\'{e} and the of Micciancio and Voulgaris, while heuristically we expect to find a
shortest vector in time , improving upon the classical time
complexity of of Wang et al. These quantum complexities
will be an important guide for the selection of parameters for post-quantum
cryptosystems based on the hardness of the shortest vector problem.Comment: 19 page
Faster Enumeration-based Lattice Reduction:Root Hermite Factor k1/(2k) Time kk/8+o(k)
International audienc
Large eddy simulation of two-dimensional isotropic turbulence
Large eddy simulation (LES) of forced, homogeneous, isotropic,
two-dimensional (2D) turbulence in the energy transfer subrange is the subject
of this paper. A difficulty specific to this LES and its subgrid scale (SGS)
representation is in that the energy source resides in high wave number modes
excluded in simulations. Therefore, the SGS scheme in this case should assume
the function of the energy source. In addition, the controversial requirements
to ensure direct enstrophy transfer and inverse energy transfer make the
conventional scheme of positive and dissipative eddy viscosity inapplicable to
2D turbulence. It is shown that these requirements can be reconciled by
utilizing a two-parametric viscosity introduced by Kraichnan (1976) that
accounts for the energy and enstrophy exchange between the resolved and subgrid
scale modes in a way consistent with the dynamics of 2D turbulence; it is
negative on large scales, positive on small scales and complies with the basic
conservation laws for energy and enstrophy. Different implementations of the
two-parametric viscosity for LES of 2D turbulence were considered. It was found
that if kept constant, this viscosity results in unstable numerical scheme.
Therefore, another scheme was advanced in which the two-parametric viscosity
depends on the flow field. In addition, to extend simulations beyond the limits
imposed by the finiteness of computational domain, a large scale drag was
introduced. The resulting LES exhibited remarkable and fast convergence to the
solution obtained in the preceding direct numerical simulations (DNS) by
Chekhlov et al. (1994) while the flow parameters were in good agreement with
their DNS counterparts. Also, good agreement with the Kolmogorov theory was
found. This LES could be continued virtually indefinitely. Then, a simplifiedComment: 34 pages plain tex + 18 postscript figures separately, uses auxilary
djnlx.tex fil
Shortest vector from lattice sieving: A few dimensions for free
Asymptotically, the best known algorithms for solving the Shortest Vector Problem (SVP) in a lattice of dimension n are sieve algorithms, which have heuristic complexity estimates ranging from (4/3)n+o(n) down to (3/2)n/2+o(n) when Locality Sensitive Hashing techniques are used. Sieve algorithms are however outperformed by pruned enumeration algorithms in practice by several orders of magnitude, despite the larger super-exponential asymptotical complexity 2Î(n log n) of the latter. In this work, we show a concrete improvement of sieve-type algorithms. Precisely, we show that a few calls to the sieve algorithm in lattices of dimension less than n - d solves SVP in dimension n, where d = Î(n/ log n). Although our improvement is only sub-exponential, its practical effect in relevant dimensions is quite significant. We implemented it over a simple sieve algorithm with (4/3)n+o(n) complexity, and it outperforms the best sieve algorithms from the literature by a factor of 10 in dimensions 7080. It performs less than an order of magnitude slower than pruned enumeration in the same range. By design, this improvement can also be applied to most other variants of sieve algorithms, including LSH sieve algorithms and tuple-sieve algorithms. In this light, we may expect sieve-techniques to outperform pruned enumeration in practice in the near future
Slide reduction, revisitedâfilling the gaps in svp approximation
We show how to generalize Gama and Nguyen's slide reduction algorithm [STOC
'08] for solving the approximate Shortest Vector Problem over lattices (SVP).
As a result, we show the fastest provably correct algorithm for
-approximate SVP for all approximation factors . This is the range of approximation factors most
relevant for cryptography
On the performance of deep learning models for time series classification in streaming
Processing data streams arriving at high speed requires the development of
models that can provide fast and accurate predictions. Although deep neural
networks are the state-of-the-art for many machine learning tasks, their
performance in real-time data streaming scenarios is a research area that has
not yet been fully addressed. Nevertheless, there have been recent efforts to
adapt complex deep learning models for streaming tasks by reducing their
processing rate. The design of the asynchronous dual-pipeline deep learning
framework allows to predict over incoming instances and update the model
simultaneously using two separate layers. The aim of this work is to assess the
performance of different types of deep architectures for data streaming
classification using this framework. We evaluate models such as multi-layer
perceptrons, recurrent, convolutional and temporal convolutional neural
networks over several time-series datasets that are simulated as streams. The
obtained results indicate that convolutional architectures achieve a higher
performance in terms of accuracy and efficiency.Comment: Paper submitted to the 15th International Conference on Soft
Computing Models in Industrial and Environmental Applications (SOCO 2020
Involvement of formyl peptide receptors in the stimulatory effect of crotoxin on macrophages co-cultivated with tumour cells
Crotoxin (CTX) is the main neurotoxic component of Crotalus durissus terrificus snake venom. It inhibits tumour growth and modulates the function of macrophages, which are essential cells in the tumour microenvironment. the present study investigated the effect of CTX on the secretory activity of monocultured macrophages and macrophages co-cultivated with LLC-WRC 256 cells. the effect of the macrophage secretory activities on tumour cell proliferation was also evaluated. Macrophages pre-treated with CTX (0.3 mu g/mL) for 2 h were co-cultivated with LLC-WRC 256 cells, and the secretory activity of the macrophages was determined after 12, 24 and 48 h. the co-cultivation of CTX-treated macrophages with the tumour cells caused a 20% reduction in tumour cell proliferation. the production of both H2O2 and NO was increased by 41% and 29% after 24 or 48 h of co-cultivation, respectively, compared to the values for the co-cultures of macrophages of control. the level of secreted IL-1 beta increased by 3.7- and 3.2-fold after 12 h and 24 h of co-cultivation, respectively. Moreover, an increased level of LXA(4) (25%) was observed after 24 h of co-cultivation, and a 2.3- and 2.1-fold increased level of 15-epi-LXA(4) was observed after 24 h and 48 h, respectively. Boc-2, a selective antagonist of formyl peptide receptors, blocked both the stimulatory effect of CTX on the macrophage secretory activity and the inhibitory effect of these cells on tumour cell proliferation. Taken together, these results indicate that CTX enhanced the secretory activity of macrophages, which may contribute to the antitumour activity of these cells, and that activation of formyl peptide receptors appears to play a major role in this effect. (C) 2013 Elsevier B.V. All rights reserved.Fundação de Amparo Ă Pesquisa do Estado de SĂŁo Paulo (FAPESP)Conselho Nacional de Desenvolvimento CientĂfico e TecnolĂłgico (CNPq)PAPInstituto Nacional de Ciencia e Tecnologia em ToxinasButantan Inst, Lab Pathophysiol, BR-05503900 SĂŁo Paulo, BrazilUniversidade Federal de SĂŁo Paulo, Lab Inflammat & Vasc Pharmacol, BR-09913030 Diadema, SP, BrazilUniv SĂŁo Paulo, Fac Med, BR-01246000 SĂŁo Paulo, BrazilUniv SĂŁo Paulo, Inst Biomed Sci, Dept Anat, BR-05508900 SĂŁo Paulo, BrazilUniv SĂŁo Paulo, Inst Biomed Sci, Dept Physiol & Biophys, BR-05508900 SĂŁo Paulo, BrazilButantan Inst, Special Lab Pain & Signaling, BR-05503900 SĂŁo Paulo, BrazilUniversidade Federal de SĂŁo Paulo, Lab Inflammat & Vasc Pharmacol, BR-09913030 Diadema, SP, BrazilFAPESP: 09/52330-9Instituto Nacional de Ciencia e Tecnologia em Toxinas: INCTTOX 2008/57898-0Web of Scienc
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