284 research outputs found
3DVerifier: Efficient Robustness Verification for 3D Point Cloud Models
3D point cloud models are widely applied in safety-critical scenes, which
delivers an urgent need to obtain more solid proofs to verify the robustness of
models. Existing verification method for point cloud model is time-expensive
and computationally unattainable on large networks. Additionally, they cannot
handle the complete PointNet model with joint alignment network (JANet) that
contains multiplication layers, which effectively boosts the performance of 3D
models. This motivates us to design a more efficient and general framework to
verify various architectures of point cloud models. The key challenges in
verifying the large-scale complete PointNet models are addressed as dealing
with the cross-non-linearity operations in the multiplication layers and the
high computational complexity of high-dimensional point cloud inputs and added
layers. Thus, we propose an efficient verification framework, 3DVerifier, to
tackle both challenges by adopting a linear relaxation function to bound the
multiplication layer and combining forward and backward propagation to compute
the certified bounds of the outputs of the point cloud models. Our
comprehensive experiments demonstrate that 3DVerifier outperforms existing
verification algorithms for 3D models in terms of both efficiency and accuracy.
Notably, our approach achieves an orders-of-magnitude improvement in
verification efficiency for the large network, and the obtained certified
bounds are also significantly tighter than the state-of-the-art verifiers. We
release our tool 3DVerifier via https://github.com/TrustAI/3DVerifier for use
by the community
A Binary Orbit for the Massive, Evolved Star HDE 326823, a WR+O System Progenitor
The hot star HDE 326823 is a candidate transition-phase object that is
evolving into a nitrogen-enriched Wolf-Rayet star. It is also a known
low-amplitude, photometric variable with a 6.123 d period. We present new, high
and moderate resolution spectroscopy of HDE 326823, and we show that the
absorption lines show coherent Doppler shifts with this period while the
emission lines display little or no velocity variation. We interpret the
absorption line shifts as the orbital motion of the apparently brighter star in
a close, interacting binary. We argue that this star is losing mass to a mass
gainer star hidden in a thick accretion torus and to a circumbinary disk that
is the source of the emission lines. HDE 326823 probably belongs to a class of
objects that produce short-period WR+O binaries.Comment: 32 pages, 10 figures, accepted to the Astronomical Journa
Cost-Effectiveness of Routine Screening for Cardiac Toxicity in Patients Treated with Imatinib in Brazil
AbstractWe performed a cost-effectiveness study of different strategies of screening for cardiotoxicity in patients receiving imatinib, the first strategy based on yearly echocardiograms in all patients and the second strategy based on yearly B-type natriuretic peptide level measurement, reserving echocardiograms for patients with an abnormal test result. Results are presented in terms of additional cost per diagnosis as compared with not performing any screening. From the Brazilian private sector’s perspective, strategies 1 and 2 resulted in additional costs of US 19,925.64 per diagnosis of cardiotoxicity, respectively. From the perspective of the Brazilian public health system, the same strategies generated additional costs of US 20,232.87 per diagnosis, respectively. In our study, systematic screening for cardiotoxicity in patients using imatinib has a high cost per diagnosis. If screening is to be adopted, a strategy based on B-type natriuretic peptide level measurement, reserving echocardiography for patients with abnormal results, results in lower costs per diagnosis in the private sector. From the public health system’s perspective, costs per diagnosis will greatly depend on the reimbursement values adopted for B-type natriuretic peptide level measurement
Potential changes in the connectivity of marine protected areas driven by extreme ocean warming
Projected future climate scenarios anticipate a warmer tropical ocean and changes in surface currents that will likely influence the survival of marine organisms and the connectivity of marine protected areas (MPAs) networks. We simulated the regional effects of climate change on the demographic connectivity of parrotfishes in nine MPAs in the South Atlantic through downscaling of the HadGEM2-ES Earth System Model running the RCP 8.5 greenhouse gas trajectory. Results indicate a tropicalization scenario over the tropical southwest Atlantic following an increase of sea surface temperature (SST) between 1.8 and 4.5 °C and changes in mean surface currents between − 0.6 to 0.5 m s−1 relative to present conditions. High mortality rates will reduce demographic connectivity and increase the isolation of oceanic islands. The simulation of organismal response to ocean warming shows that acclimation can significantly improve (p < 0.001) particle survival, promoting connectivity and tropicalization of MPAs, with potential impacts on their functional integrity and long-term resilience.publishedVersio
Mass loss from inhomogeneous hot star winds II. Constraints from a combined optical/UV study
Mass-loss rates currently in use for hot, massive stars have recently been
seriously questioned, mainly because of the effects of wind clumping. We
investigate the impact of clumping on diagnostic ultraviolet resonance and
optical recombination lines. Optically thick clumps, a non-void interclump
medium, and a non-monotonic velocity field are all accounted for in a single
model. We used 2D and 3D stochastic and radiation-hydrodynamic (RH) wind
models, constructed by assembling 1D snapshots in radially independent slices.
To compute synthetic spectra, we developed and used detailed radiative transfer
codes for both recombination lines (solving the "formal integral") and
resonance lines (using a Monte-Carlo approach). In addition, we propose an
analytic method to model these lines in clumpy winds, which does not rely on
optically thin clumping. Results: Synthetic spectra calculated directly from
current RH wind models of the line-driven instability are unable to in parallel
reproduce strategic optical and ultraviolet lines for the Galactic O-supergiant
LCep. Using our stochastic wind models, we obtain consistent fits essentially
by increasing the clumping in the inner wind. A mass-loss rate is derived that
is approximately two times lower than predicted by the line-driven wind theory,
but much higher than the corresponding rate derived from spectra when assuming
optically thin clumps. Our analytic formulation for line formation is used to
demonstrate the potential impact of optically thick clumping in weak-winded
stars and to confirm recent results that resonance doublets may be used as
tracers of wind structure and optically thick clumping. (Abridged)Comment: 14 pages+1 Appendix, 8 figures, 3 tables. Accepted for publication in
Astronomy and Astrophysics. One reference updated, minor typo in Appendix
correcte
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