Ensemble machine learning model for automated asteroid detection

The potential threat of Near Earth Objects (NEO) requires a constant survey of the night sky to discover potentially dangerous objects and assess their future impact odds. Several ongoing surveys relying on human operators or automated techniques exist. One such example is the EURONEAR blink mini-survey project which over time developed from a pure manual approach to detecting asteroids to semi-automatic methods (NEARBY) using image processing and service-oriented approaches. In this paper, we propose an extension of NEARBY based on an ensemble model comprising three state-of-art machine learning models, some used in similar approaches. The proposed model is designed for a binary classification problem where candidate images may contain an asteroid in their center. Validation on a real-life dataset comprising 11,000 images shows that our ensemble model is capable of recovering about 55% of the asteroids missed by the previous NEARBY automated process while at the same time having a 0.88 recall on the asteroids already detected by NEARBY. Used together with NEARBY our model increased the detection rate from 89% to 95%

Outflow mechanisms after deep sclerectomy with two different designs of collagen implant in an animal model

BACKGROUND: To study experimentally two different shapes of collagen implants (CI) used in deep sclerectomy (DS). The ability to promote drainage vessels, outflow mechanisms, success rates, and biodegradability, were studied prospectively in an animal model. MATERIALS AND METHODS: DS was performed in 20 eyes of ten rabbits. Each rabbit randomly received a cylindrical CI in one eye, while the other eye received a flat CI. Intraocular pressure (IOP) measurement, ultrasound biomicroscopy (UBM) examination of DS site and simultaneous fluorescein and indocyanin green anterior-segment angiography were performed preoperatively, at 1 and 2 weeks, 1, 2, 3, 6 and 9 months for each eye. At the end of the follow-up period, outflow facility (OF) was measured and histological examinations of the filtration site were performed. RESULTS: In the cylindrical implant group, IOP significantly dropped from a mean pre-operative value of 14.8+/-2.2 mmHg to a mean postoperative values of 10.9+/-3.3, 12.5+/-2.2, 11.8+/-2.6, 11.2+/-2.3, 10.7+/-1.9, 14.0+/- 3.2, 12.6+/-2.4 mmHg at 1, 2 weeks, and 1, 2, 3, 6, and 9 months, respectively. In the flat CI group, IOP significantly dropped from a mean preoperative value of 14.1+/-1.8 mmHg to a mean postoperative values of 10.4+/-2.7, 12.7+/-1.9, 12.5+/-3.2, 11.2+/-1.6, 11.6+/-1.8, 11.5+/-2.3, 11.0+/-2.2 mmHg at 1, 2 weeks, and at 1, 2, 3, 6, and 9 months, respectively. UBM images showed a gradual resorption of both type of CI during the first 3 months, and angiographies showed progressive growth of drainage vessels around the filtration site in both groups. The mean OF 9 months postoperatively for the cylindrical CI was 0.53 (SD +/- 0.23) ml/ min per mmHg and was 0.56 (SD+/-0.17) ml/min per mmHg for the flat CI (P=0.6). Histological examination revealed excellent biocompatibilty and a high density of drainage vessels in the sclera around the operative site in both groups. CONCLUSION: Using IOP and OF measurements, UBM, angiography, and histology, we were able to compare two types of CI used as space maintainer in DS. Both CIs showed efficient IOP lowering effect and outflow facility increase, possibly explained by stimulation of drainage vessels growth. Both implants showed excellent biocompatibility. The flat CI showed a slight tendency towards better overall performances

Asymptotic Distribution Theory for Break Point Estimators in Models Estimated via 2SLS

In this paper, we present a limiting distribution theory for the break point estimator in a linear regression model with multiple structural breaks obtained by minimizing a Two Stage Least Squares (2SLS) objective function. Our analysis covers both the case in which the reduced form for the endogenous regressors is stable and the case in which it is unstable with multiple structural breaks. For stable reduced forms, we present a limiting distribution theory under two different scenarios: in the case where the parameter change is of fixed magnitude, it is shown that the resulting distribution depends on the distribution of the data and is not of much practical use for inference; in the case where the magnitude of the parameter change shrinks with the sample size, it is shown that the resulting distribution can be used to construct approximate large sample confidence intervals for the break points. For unstable reduced forms, we consider the case where the magnitudes of the parameter changes in both the equation of interest and the reduced forms shrink with the sample size at potentially different rates and not necessarily the same locations in the sample. The resulting limiting distribution theory can be used to construct approximate large sample confidence intervals for the break points. The finite sample performance of these intervals are analyzed in a small simulation study and the intervals are illustrated via an application to the New Keynesian Phillips curve

The dependence of the anomalous J/psi suppression on the number of participant nucleons

The observation of an anomalous J/psi suppression in Pb-Pb collisions by the NA50 Collaboration can be considered as the most striking indication for the deconfinement of quarks and gluons at SPS energies. In this Letter, we determine the J/psi suppression pattern as a function of the forward hadronic energy E-ZDC measured in a Zero Degree Calorimeter (ZDC). The direct connection between EZDC and the geometry of the collision allows us to calculate, within a Glauber approach, the precise relation between the number of participant nucleons N-part and E-ZDC. Then, we check if the experimental data can be better explained by a sudden or a smooth onset of the anomalous J/psi suppression as a function of the number of participants. (C) 2001 Elsevier Science B.V. All rights reserved.info:eu-repo/semantics/publishedVersio

J/psi azimuthal anisotropy relative to the reaction plane in Pb-Pb collisions at 158 GeV per nucleon

The J/$\psi$ azimuthal distribution relative to the reaction plane has been measured by the NA50 experiment in Pb-Pb collisions at 158 GeV/nucleon. Various physical mechanisms related to charmonium dissociation in the medium created in the heavy ion collision are expected to introduce an anisotropy in the azimuthal distribution of the observed J/$\psi$ mesons at SPS energies. Hence, the measurement of J/$\psi$ elliptic anisotropy, quantified by the Fourier coefficient v$_2$ of the J/$\psi$ azimuthal distribution relative to the reaction plane, is an important tool to constrain theoretical models aimed at explaining the anomalous J/$\psi$ suppression observed in Pb-Pb collisions. We present the measured J/$\psi$ yields in different bins of azimuthal angle relative to the reaction plane, as well as the resulting values of the Fourier coefficient v$_{2}$ as a function of the collision centrality and of the J/$\psi$ transverse momentum. The reaction plane has been estimated from the azimuthal distribution of the neutral transverse energy detected in an electromagnetic calorimeter. The analysis has been performed on a data sample of about 100 000 events, distributed in five centrality or p$_{\rm T}$ sub-samples. The extracted v$_{2}$ values are significantly larger than zero for non-central collisions and are seen to increase with p$_{\rm T}$.Comment: proceedings of HP08 conference corrected a typo in one equatio

Centrality Behaviour of J/ψ\psi Production in Na50

The J/$\psi$ production in 158 A GeV Pb-Pb interactions is studied, in the dimuon decay channel, as a function of centrality, as measured with the electromagnetic or with the very forward calorimeters. After a first sharp variation at mid centrality, both patterns continue to fall down and exhibit a curvature change at high centrality values. This trend excludes any conventional hadronic model and is in agreement with a deconfined quark-gluon phase scenario. We report also preliminary results on the measured charged multiplicity, as given by a dedicated detector.Comment: 5 pages, 7 figures (in eps) talk given at XXXI International Symposium on Multiparticle Dynamics, Sep. 1-7, 2001, Datong China URL http://ismd31.ccnu.edu.cn

280 one-opposition near-Earth asteroids recovered by the EURONEAR with the <i>Isaac Newton</i> Telescope

Context. One-opposition near-Earth asteroids (NEAs) are growing in number, and they must be recovered to prevent loss and mismatch risk, and to improve their orbits, as they are likely to be too faint for detection in shallow surveys at future apparitions. Aims. We aimed to recover more than half of the one-opposition NEAs recommended for observations by the Minor Planet Center (MPC) using the Isaac Newton Telescope (INT) in soft-override mode and some fractions of available D-nights. During about 130 h in total between 2013 and 2016, we targeted 368 NEAs, among which 56 potentially hazardous asteroids (PHAs), observing 437 INT Wide Field Camera (WFC) fields and recovering 280 NEAs (76% of all targets). Methods. Engaging a core team of about ten students and amateurs, we used the THELI, Astrometrica, and the Find_Orb software to identify all moving objects using the blink and track-and-stack method for the faintest targets and plotting the positional uncertainty ellipse from NEODyS. Results. Most targets and recovered objects had apparent magnitudes centered around V ~ 22.8 mag, with some becoming as faint as V ~ 24 mag. One hundred and three objects (representing 28% of all targets) were recovered by EURONEAR alone by Aug. 2017. Orbital arcs were prolonged typically from a few weeks to a few years; our oldest recoveries reach 16 years. The O−C residuals for our 1854 NEA astrometric positions show that most measurements cluster closely around the origin. In addition to the recovered NEAs, 22 000 positions of about 3500 known minor planets and another 10 000 observations of about 1500 unknown objects (mostly main-belt objects) were promptly reported to the MPC by our team. Four new NEAs were discovered serendipitously in the analyzed fields and were promptly secured with the INT and other telescopes, while two more NEAs were lost due to extremely fast motion and lack of rapid follow-up time. They increase the counting to nine NEAs discovered by the EURONEAR in 2014 and 2015. Conclusions. Targeted projects to recover one-opposition NEAs are efficient in override access, especially using at least two-meter class and preferably larger field telescopes located in good sites, which appear even more efficient than the existing surveys

A new measurement of J/psi suppression in Pb-Pb collisions at 158 GeV per nucleon

We present a new measurement of J/psi production in Pb-Pb collisions at 158 GeV/nucleon, from the data sample collected in year 2000 by the NA50 Collaboration, under improved experimental conditions with respect to previous years. With the target system placed in vacuum, the setup was better adapted to study, in particular, the most peripheral nuclear collisions with unprecedented accuracy. The analysis of this data sample shows that the (J/psi)/Drell-Yan cross-sections ratio measured in the most peripheral Pb-Pb interactions is in good agreement with the nuclear absorption pattern extrapolated from the studies of proton-nucleus collisions. Furthermore, this new measurement confirms our previous observation that the (J/psi)/Drell-Yan cross-sections ratio departs from the normal nuclear absorption pattern for semi-central Pb-Pb collisions and that this ratio persistently decreases up to the most central collisions.Comment: 19 pages, 10 figures. Submitted to Eur. Phys. J.

Discovery and physical characterization as the first response to a potential asteroid collision: The case of 2023 DZ2

Near-Earth asteroids (NEAs) that may evolve into impactors deserve detailed threat assessment studies. Early physical characterization of a would-be impactor may help in optimizing impact mitigation plans. We first detected NEA 2023~DZ$_{2}$ on 27--February--2023. After that, it was found to have a Minimum Orbit Intersection Distance (MOID) with Earth of 0.00005~au as well as an unusually high initial probability of becoming a near-term (in 2026) impactor. We aim to perform a rapid but consistent dynamical and physical characterization of 2023~DZ$_{2}$ as an example of a key response to mitigate the consequences of a potential impact. We use a multi-pronged approach, drawing from various methods (observational/computational) and techniques (spectroscopy/photometry from multiple instruments), and bringing the data together to perform a rapid and robust threat assessment.} The visible reflectance spectrum of 2023~DZ$_{2}$ is consistent with that of an X-type asteroid. Light curves of this object obtained on two different nights give a rotation period $P$=6.2743$\pm$0.0005 min with an amplitude $A$=0.57$\pm$0.14~mag. We confirm that although its MOID is among the smallest known, 2023~DZ$_{2}$ will not impact Earth in the foreseeable future as a result of secular near-resonant behaviour. Our investigation shows that coordinated observation and interpretation of disparate data provides a robust approach from discovery to threat assessment when a virtual impactor is identified. We prove that critical information can be obtained within a few days after the announcement of the potential impactor.Comment: Accepted for publication in Astronomy and Astrophysics, 15 page

Bottomonium and Drell-Yan production in p-A collisions at 450 GeV

The NA50 Collaboration has measured heavy-quarkonium production in p-A collisions at 450 GeV incident energy (sqrt(s) = 29.1 GeV). We report here results on the production of the Upsilon states and of high-mass Drell-Yan muon pairs (m > 6 GeV). The cross-section at midrapidity and the A-dependence of the measured yields are determined and compared with the results of other fixed-target experiments and with the available theoretical estimates. Finally, we also address some issues concerning the transverse momentum distributions of the measured dimuons.Comment: 18 pages, 9 figures, to be published in Phys. Lett.