202 research outputs found
Physical and dynamical characterisation of low Delta-V NEA (190491) 2000 FJ10
We investigated the physical properties and dynamical evolution of Near Earth
Asteroid (NEA) (190491) 2000 FJ10 in order to assess the suitability of this
accessible NEA as a space mission target. Photometry and colour determination
were carried out with the 1.54 m Kuiper Telescope and the 10 m Southern African
Large Telescope during the object's recent favourable apparition in 2011-12.
During the earlier 2008 apparition, a spectrum of the object in the 6000-9000
Angstrom region was obtained with the 4.2 m William Herschel Telescope.
Interpretation of the observational results was aided by numerical simulations
of 1000 dynamical clones of 2000 FJ10 up to 10^6 yr in the past and in the
future. The asteroid's spectrum and colours determined by our observations
suggest a taxonomic classification within the S-complex although other
classifications (V, D, E, M, P) cannot be ruled out. On this evidence, it is
unlikely to be a primitive, relatively unaltered remnant from the early history
of the solar system and thus a low priority target for robotic sample return.
Our photometry placed a lower bound of 2 hrs to the asteroid's rotation period.
Its absolute magnitude was estimated to be 21.54+-0.1 which, for a typical
S-complex albedo, translates into a diameter of 130+-20 m. Our dynamical
simulations show that it has likely been an Amor for the past 10^5 yr. Although
currently not Earth-crossing, it will likely become so during the period 50 -
100 kyr in the future. It may have arrived from the inner or central Main Belt
> 1 Myr ago as a former member of a low-inclination S-class asteroid family.
Its relatively slow rotation and large size make it a suitable destination for
a human mission. We show that ballistic Earth-190491-Earth transfer
trajectories with Delta-V < 2 km s^-1 at the asteroid exist between 2052 and
2061.Comment: 2 Tables, 11 Figures, accepted for publication in Astronomy &
Astrophysic
MN Draconis - peculiar, active dwarf nova in the period gap
Context: We present results of an extensive world-wide observing campaign of
MN Draconis.
Aims: MN Draconis is a poorly known active dwarf nova in the period gap and
is one of the only two known cases of period gap SU UMa objects showing the
negative superhumps. Photometric behaviour of MN Draconis poses a challenge for
existing models of the superhump and superoutburst mechanisms. Therefore,
thorough investigation of peculiar systems, such as MN Draconis, is crucial for
our understanding of evolution of the close binary stars.
Methods: To measure fundamental parameters of the system, we collected
photometric data in October 2009, June-September 2013 and June-December 2015.
Analysis of the light curves, diagrams and power spectra was carried out.
Results: During our three observational seasons we detected four
superoutburts and several normal outbursts. Based on the two consecutive
superoutbursts detected in 2015, the supercycle length was derived P_sc = 74
+/- 0.5 days and it has been increasing with a rate of P_dot = 3.3 x 10^(-3)
during last twelve years. Based on the positive and negative superhumps we
calculated the period excess epsilon = 5.6% +/- 0.1%, the period deficit
epsilon_ = 2.5% +/- 0.6%, and in result, the orbital period P_orb = 0.0994(1)
days (143.126 +/- 0.144 min). We updated the basic light curve parameters of MN
Draconis.
Conclusions: MN Draconis is the first discovered SU UMa system in the period
gap with increasing supercycle length.Comment: 14 pages, 20 figures, 8 tables, accepted for publication in Astronomy
and Astrophysic
EP-1171 Blood parameters as prognosticators in radiochemotherapy for non-small cell lung cancer
Acoustic localisation of wildlife with low-cost equipment: Lower sensitivity, but no loss of precision
Abstract Context Synchronised acoustic recorders can be used as a non-invasive tool to detect and localise sounds of interest, including vocal wildlife and anthropogenic sounds. Due to the high cost of commercial synchronised recorders, acoustic localisation has typically been restricted to small or well funded surveys. Recently, low-cost acoustic recorders have been developed, but until now their efficacy has not been compared with higher specification recorders. Aims The present study aimed to compare the efficacy of a newly developed low-cost recorder, the Conservation at Range through Audio Classification and Localisation (CARACAL), with an established, high-end recorder, the Wildlife Acoustics Song Meter (SM). Methods Four recorders of each type were deployed in a paired set-up across five nights in Wisconsin, USA. The recordings allowed for manual identification of domestic dog (Canis familiaris), grey wolf (Canis lupus), coyote (Canis latrans) and barred owl (Strix varia) calls, and then the ability of each recorder type to detect and localise the vocalising animals was compared. Key results The CARACALs were less sensitive, detecting only 47.5% of wolf, 55% of coyote, 65% of barred owl and 82.5% of dog vocalisations detected by the paired SMs. However, when the same vocalisations were detected on both recorders, localisation was comparable, with no significant difference in the precision or maximum detection ranges. Conclusions Low-cost recording equipment can be used effectively for acoustic localisation of both wild and domestic animals. However, the lower sensitivity of the CARACALs means that a denser network of these recorders would be needed to achieve the same efficacy as the SMs. Deploying a greater number of cheaper recorders increases the labour time in the field and the quantity of data to process and store. Thus, there is a trade-off between cost and time to be considered. Implications The ability to use low-cost recorders for acoustic localisation provides new avenues for tracking, managing and researching a wide range of wildlife species. Presently, CARACALs are more suited to monitoring species that have small home ranges and high amplitude vocalisations, and for when a large time investment for in situ equipment checks and data processing is feasible.Christine Stevens Wildlife Award from the Animal Welfare Institut
Large halloween asteroid at lunar distance
The near-Earth asteroid (NEA) 2015 TB had a very close encounter with Earth at 1.3 lunar distances on October 31, 2015. We obtained 3-band mid-infrared observations of this asteroid with the ESO VLT-VISIR instrument covering approximately four hours in total. We also monitored the visual lightcurve during the close-encounter phase. The NEA has a (most likely) rotation period of 2.939 ± 0.005 h and the visual lightcurve shows a peak-to-peak amplitude of approximately 0.12 ± 0.02 mag. A second rotation period of 4.779 ± 0.012 h, with an amplitude of the Fourier fit of 0.10 ± 0.02 mag, also seems compatible with the available lightcurve measurements. We estimate a V-R colour of 0.56 ± 0.05 mag from different entries in the MPC database. A reliable determination of the object's absolute magnitude was not possible. Applying different phase relations to the available R-/V-band observations produced H = 18.6 mag (standard H-G calculations) or H = 19.2 mag and H = 19.8 mag (via the H-G procedure for sparse and low-quality data), with large uncertainties of approximately 1 mag. We performed a detailed thermophysical model analysis by using spherical and partially also ellipsoidal shape models. The thermal properties are best explained by an equator-on (± 30°) viewing geometry during our measurements with a thermal inertia in the range 250-700 J m s K (retrograde rotation) or above 500 J m s K (prograde rotation). We find that the NEA has a minimum size of approximately 625 m, a maximum size of just below 700 m, and a slightly elongated shape with a/b 1.1. The best match to all thermal measurements is found for: (i) thermal inertia Γ = 900 J m s K; D = 644 m, p = 5.5% (prograde rotation with 2.939 h); regolith grain sizes of 50-100 mm; (ii) thermal inertia Γ = 400 J m s K; D = 667 m, p = 5.1% (retrograde rotation with 2.939 h); regolith grain sizes of 10-20 mm. A near-Earth asteroid model (NEATM) confirms an object size well above 600 m (best NEATM solution at 690 m, beaming parameter η = 1.95), significantly larger than early estimates based on radar measurements. In general, a high-quality physical and thermal characterisation of a close-encounter object from two-week apparition data is not easily possible. We give recommendations for improved observing strategies for similar events in the future. © ESO, 2017.The research leading to these results has received funding from the European Union's Horizon 2020 Research and Innovation Programme, under Grant Agreement No. 687378. Funding from Spanish grant AYA-2014-56637-C2-1-P is acknowledged. Hungarian funding from the NKFIH grant GINOP-2.3.2-15-2016-00003 is also acknowledged. R.D. acknowledges the support of MINECO for his Ramon y Cajal Contract.Peer Reviewe
Thermal properties of large main-belt asteroids observed by Herschel PACS
Non-resolved thermal infrared observations enable studies of thermal and
physical properties of asteroid surfaces provided the shape and rotational
properties of the target are well determined via thermo-physical models. We
used calibration-programme Herschel PACS data (70, 100, 160 m) and
state-of-the-art shape models derived from adaptive-optics observations and/or
optical light curves to constrain for the first time the thermal inertia of
twelve large main-belt asteroids. We also modelled previously
well-characterised targets such as (1) Ceres or (4) Vesta as they constitute
important benchmarks. Using the scale as a free parameter, most targets
required a re-scaling 5\% consistent with what would be expected given
the absolute calibration error bars. This constitutes a good cross-validation
of the scaled shape models, although some targets required larger re-scaling to
reproduce the IR data. We obtained low thermal inertias typical of large main
belt asteroids studied before, which continues to give support to the notion
that these surfaces are covered by fine-grained insulating regolith. Although
the wavelengths at which PACS observed are longwards of the emission peak for
main-belt asteroids, they proved to be extremely valuable to constrain size and
thermal inertia and not too sensitive to surface roughness. Finally, we also
propose a graphical approach to help examine how different values of the
exponent used for scaling the thermal inertia as a function of heliocentric
distance (i.e. temperature) affect our interpretation of the results.Comment: Accepted for publication in Astronomy & Astrophysics (preprint
version
Polymorphisms in Nucleotide Excision Repair Genes, Arsenic Exposure, and Non-Melanoma Skin Cancer in New Hampshire
Background: Arsenic exposure may alter the efficiency of DNA repair. UV damage is specifically repaired by nucleotide excision repair (NER), and common genetic variants in NER may increase risk for non-melanoma skin cancer (NMSC). Objective: We tested whether polymorphisms in the NER genes XPA (A23G) and XPD (Asp312Asn and Lys751Gln) modify the association between arsenic and NMSC. Methods: Incident cases of basal and squamous cell carcinoma (BCC and SCC, respectively) were identified through a network of dermatologists and pathology laboratories across New Hampshire. Population-based controls were frequency matched to cases on age and sex. Arsenic exposure was assessed in toenail clippings. The analysis included 880 cases of BCC, 666 cases of SCC, and 780 controls. Results: There was an increased BCC risk associated with high arsenic exposure among those homozygous variant for XPA [odds ratio (OR) = 1.8; 95% confidence interval (CI), 0.9–3.7]. For XPD, having variation at both loci (312Asn and 751Gln) occurred less frequently among BCC and SCC cases compared with controls (OR = 0.8; 95% CI, 0.6–1.0) for both case groups. In the stratum of subjects who have variant for both XPD polymorphisms, there was a 2-fold increased risk of SCC associated with elevated arsenic (OR = 2.2; 95% CI, 1.0–5.0). The test for interaction between XPD and arsenic in SCC was of borderline significance (p < 0.07, 3 degrees of freedom). Conclusions: Our findings indicate a reduced NMSC risk in relation to XPD Asp312Asn and Lys751Gln variants. Further, these data support the hypothesis that NER polymorphisms may modify the association between NMSC and arsenic
XPD gene polymorphism and host characteristics in the association with cutaneous malignant melanoma risk
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