1,564 research outputs found
Deep Chandra Observations of HCG 16 - I. Active Nuclei, Star formation and Galactic Winds
We present new, deep Chandra X-ray and Giant Metrewave Radio Telescope
610~MHz observations of the spiral-galaxy-rich compact group HCG 16, which we
use to examine nuclear activity, star formation and the high luminosity X-ray
binary populations in the major galaxies. We confirm the presence of obscured
active nuclei in NGC 833 and NGC 835, and identify a previously unrecognized
nuclear source in NGC 838. All three nuclei are variable on timescales of
months to years, and for NGC 833 and NGC 835 this is most likely caused by
changes in accretion rate. The deep Chandra observations allow us to detect for
the first time an Fe-K emission line in the spectrum of the Seyfert 2
nucleus of NGC 835. We find that NGC 838 and NGC 839 are both
starburst-dominated systems, with only weak nuclear activity, in agreement with
previous optical studies. We estimate the star formation rates in the two
galaxies from their X-ray and radio emission, and compare these results with
estimates from the infra-red and ultra-violet bands to confirm that star
formation in both galaxies is probably declining after galaxy-wide starbursts
were triggered ~400-500 Myr ago. We examine the physical properties of their
galactic superwinds, and find that both have temperatures of ~0.8 keV. We also
examine the X-ray and radio properties of NGC 848, the fifth largest galaxy in
the group, and show that it is dominated by emission from its starburst.Comment: 18 pages, 11 figures, 11 tables, accepted for publication in ApJ;
updated references and fixed typos identified at proof stag
Flow-based detection and proxy-based evasion of encrypted malware C2 traffic
State of the art deep learning techniques are known to be vulnerable to
evasion attacks where an adversarial sample is generated from a malign sample
and misclassified as benign. Detection of encrypted malware command and control
traffic based on TCP/IP flow features can be framed as a learning task and is
thus vulnerable to evasion attacks. However, unlike e.g. in image processing
where generated adversarial samples can be directly mapped to images, going
from flow features to actual TCP/IP packets requires crafting the sequence of
packets, with no established approach for such crafting and a limitation on the
set of modifiable features that such crafting allows. In this paper we discuss
learning and evasion consequences of the gap between generated and crafted
adversarial samples. We exemplify with a deep neural network detector trained
on a public C2 traffic dataset, white-box adversarial learning, and a
proxy-based approach for crafting longer flows. Our results show 1) the high
evasion rate obtained by using generated adversarial samples on the detector
can be significantly reduced when using crafted adversarial samples; 2)
robustness against adversarial samples by model hardening varies according to
the crafting approach and corresponding set of modifiable features that the
attack allows for; 3) incrementally training hardened models with adversarial
samples can produce a level playing field where no detector is best against all
attacks and no attack is best against all detectors, in a given set of attacks
and detectors. To the best of our knowledge this is the first time that level
playing field feature set- and iteration-hardening are analyzed in encrypted C2
malware traffic detection.Comment: 9 pages, 6 figure
Utilização da cianamida hidrogenada e óleo mineral na brotação e floração de pessegueiro.
bitstream/item/43867/1/boletim-33.pd
A method to obtain orange crop geometry information using a mobile terrestrial laser scanner and 3D modeling
LiDAR (Light Detection and Ranging) technology has been used to obtain geometrical attributes of tree crops in small field plots, sometimes using manual steps in data processing. The objective of this study was to develop a method for estimating canopy volume and height based on a mobile terrestrial laser scanner suited for large commercial orange groves. A 2D LiDAR sensor and a GNSS (Global Navigation Satellite System) receiver were mounted on a vehicle for data acquisition. A georeferenced point cloud representing the laser beam impacts on the crop was created and later classified into transversal sections along the row or into individual trees. The convex-hull and the alpha-shape reconstruction algorithms were used to reproduce the shape of the tree crowns. Maps of canopy volume and height were generated for a 25 ha orange grove. The different options of data processing resulted in different values of canopy volume. The alpha-shape algorithm was considered a good option to represent individual trees whereas the convex-hull was better when representing transversal sections of the row. Nevertheless, the canopy volume and height maps produced by those two methods were similar. The proposed system is useful for site-specific management in orange groves.We thank Citrosuco and Jacto companies for supporting this project, the São Paulo Research
Foundation (FAPESP) for providing a scholarship to the first author (grant: 2013/18853-0) and the Coordination
for the Improvement of Higher Education Personnel (CAPES), for funding the first author as an exchange visitor
at the University of Lleida (grant: bex_3751/15-5
On small-noise equations with degenerate limiting system arising from volatility models
The one-dimensional SDE with non Lipschitz diffusion coefficient is widely
studied in mathematical finance. Several works have proposed asymptotic
analysis of densities and implied volatilities in models involving instances of
this equation, based on a careful implementation of saddle-point methods and
(essentially) the explicit knowledge of Fourier transforms. Recent research on
tail asymptotics for heat kernels [J-D. Deuschel, P.~Friz, A.~Jacquier, and
S.~Violante. Marginal density expansions for diffusions and stochastic
volatility, part II: Applications. 2013, arxiv:1305.6765] suggests to work with
the rescaled variable : while
allowing to turn a space asymptotic problem into a small- problem
with fixed terminal point, the process satisfies a SDE in
Wentzell--Freidlin form (i.e. with driving noise ). We prove a
pathwise large deviation principle for the process as
. As it will become clear, the limiting ODE governing the
large deviations admits infinitely many solutions, a non-standard situation in
the Wentzell--Freidlin theory. As for applications, the -scaling
allows to derive exact log-asymptotics for path functionals of the process:
while on the one hand the resulting formulae are confirmed by the CIR-CEV
benchmarks, on the other hand the large deviation approach (i) applies to
equations with a more general drift term and (ii) potentially opens the way to
heat kernel analysis for higher-dimensional diffusions involving such an SDE as
a component.Comment: 21 pages, 1 figur
FATZ, a filamin-, actinin-, and telethonin-binding protein of the Z-disc of skeletal muscle
We report the identification and characterization of a novel 32-kDa protein expressed in skeletal muscle and located in the Z-disc of the sarcomere. We found that this protein binds to three other Z-disc proteins; therefore, we have-named it FATZ, gamma -filamin/ABP-L, alpha -actinin and telethonin binding protein of the Z-disc. From yeast two-hybrid experiments we are able to show that the SR3-SR4 domains of alpha -actinin 2 are required to bind the COOH-terminal region of the FATZ as does gamma -filamin/ABP-L, Furthermore, by using a glutathione S-transferase overlay assay we find that FATZ also binds telethonin. The level of FATZ protein in muscle cells increases during differentiation, being clearly detectable before the onset of myosin, Although FATZ has no known interaction domains, it would appear to be involved in a complex network of interactions with other Z-band components. On the basis of the information known about its binding partners, we could envisage a central role for FATZ in the: myofibrillogenesis, After screening our muscle expressed sequence tag data base and the public expressed sequence tag data bases, we were able to assemble two other muscle transcripts that show a high level of identity with FATZ in two different domains. Therefore, FATZ may be the first member of a small family of novel muscle proteins
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