SORA: Stellar occultation reduction and analysis Gomes-Júnior, A R; Morgado, B E; Benedetti-Rossi, G ...
Monthly Notices of the Royal Astronomical Society,
02/2022, Letnik:
511, Številka:
1
Journal Article
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ABSTRACT
The stellar occultation technique provides competitive accuracy in determining the sizes, shapes, astrometry, etc., of the occulting body, comparable to in-situ observations by spacecraft. ...With the increase in the number of known Solar system objects expected from the LSST, the highly precise astrometric catalogs, such as Gaia, and the improvement of ephemerides, occultations observations will become more common with a higher number of chords in each observation. In the context of the Big Data era, we developed sora, an open-source python library to reduce and analyse stellar occultation data efficiently. It includes routines from predicting such events up to the determination of Solar system bodies’ sizes, shapes, and positions.
ABSTRACT
Recording a stellar occultation is one powerful method that gives direct information about the physical properties of the occulting Solar system object. In order to obtain reliable and ...accurate results, simultaneous observations from different locations across-track of the projected path are of great importance. However, organizing all the observing stations, aggregating, and analysing the data is time-consuming and not that easy. We have developed a web portal named Occultation Portal (OP) to manage all those occultation observation campaigns from a central server. With this portal, the instrumental and observational information of all observers participating in a stellar occultation campaign and the concerned data are archived systematically in a standard format. The researchers can then visualize the archived data on an event basis. The investigators can also extract the light curve for each data set with the added reduction pipeline to the portal base. This paper describes in detail the portal structure and the developed features.
In many industries, distribution activities are realised in a dynamic environment including uncertainties. Besides, adding transportation mode alternatives, inventory-stocking opportunities in ...wholesalers, unmet demand permission in distribution centres, etc. increase the difficulty of problem modelling and solving for large-scale networks. In this study, the problem of physical distribution network (DN) design with profit maximisation objective function is modelled to tackle with realistic cases. Two-stage stochastic mixed-integer programming method is used to handle the uncertainties and to consider the probable scenarios. The first-stage decisions of the proposed model are related with the selection of facility location in strategic level, and the second-stage decisions are related with the transported and stocked products or unmet demand quantities. Here, a multi-product, two-echelon, multi-mode and multi-period network model is applied to a hypothetically created problem, inspired from the physical DN of home appliance companies. Various scenarios including stochastic demand and price data with different realisation probabilities are used in the model. The motivation of this study is the lack of reaching a global optimum result using transportation modes as stochastic parameters, considering their own lead times and capacities. Finally, various results are obtained for different cases and analysed in detail.
To evaluate the safety and efficacy of percutaneous biliary stone clearance in a single hepatopancreaticobiliary (HPB) centre.
All patients who underwent percutaneous biliary stone clearance between ...2010 and 2020 at a HPB centre were identified from the radiology information system. Their demographic data, presentation, previous surgery, number/size of biliary calculi, success and complications were collected from patient records. Unpaired student's t-test was used to compare numerical variables and the Chi-square test was used to compare categorical data.
Sixty-eight patients aged between 58.5–91.1 years underwent the procedure, and 42.6% (29/68) had the procedure due to surgically altered anatomy precluding endoscopic retrograde cholangiopancreatography (ERCP). The most common presentation was cholangitis (62%). The success rate of percutaneous stone clearance was 92.7%. The average number of calculi was two (range 1–12). Of the patients included, 4.4% developed pancreatitis, 4.4% developed cholangitis, and 1.5% had hepatic artery branch pseudoaneurysm successfully treated with transarterial embolisation. There was no significant difference in success or complication rates between the different access sites (right lobe, left lobe, roux-loop, T-tube, p=0.7767).
Percutaneous biliary stone clearance is safe and effective and will continue to play an important role where ERCP fails or is impossible due surgically altered anatomy.
•Biliary calculi can be effectively treated percutaneously when ERCP is not possible.•The technique plays an important role in patients with surgically altered GI anatomy.•Percutaneous cholangioscopy & lithotripsy may facilitate treatment of larger calculi.
We were able to accurately predict the shadow path and successfully observe an occultation of a bright star by Chiron on December 15, 2022. The Kottamia Astronomical Observatory in Egypt did not ...detect the occultation by the solid body, but we found three extinction features in the light curve that had symmetrical counterparts with respect to the central time of the occultation. One of the features is broad and shallow, whereas the other two features are sharper, with a maximum extinction of ∼25% at the achieved spatial resolution of 19 km per data point. From the Wise Observatory in Israel, we detected the occultation caused by the main body and several extinction features surrounding the body. When all the secondary features are plotted in the sky plane, we find that they can be caused by a broad ∼580 km disk with concentrations at radii of 325 ± 16 km and 423 ± 11 km surrounding Chiron. At least one of these structures appears to be outside the Roche limit. The ecliptic coordinates of the pole of the disk are
λ
= 151° ±8° and
β
= 18° ±11°, in agreement with previous results. We also reveal our long-term photometry results, indicating that Chiron had suffered a brightness outburst of at least 0.6 mag between March and September 2021 and that Chiron was still somewhat brighter at the occultation date than at its nominal pre-outburst phase. The outermost extinction features might be consistent with a bound or temporarily bound structure associated with the brightness increase. However, the nature of the brightness outburst is unclear, and it is also unclear whether the dust or ice released in the outburst could be feeding a putative ring structure or whether it is emanating from it.
Context. The paper is comprised of optical identification and multiwavelength studies of a new X-ray source discovered by the Spectrum Roentgen-Gamma (SRG) observatory during the ART-XC survey and ...its follow-up optical and X-ray observations. Aims. We aim to identify SRGA J213151.5+491400 in the optical wavelengths. We determine spectra and light curves in the optical high and low states to find periodicities in the light curves and resolve emission lines in the system using optical ground-based data. We intend to study the spectral and temporal X-ray characteristics of the new source using the SRG surveys in the high and low states and NICER data in the low state. Methods. We present optical data from telescopes in Türkiye (RTT-150 and T100 at the TÜBİTAK National Observatory) and in Russia (6-m and 1-m at SAO RAS), together with the X-ray data obtained with ART-XC and eROSITA telescopes aboard SRG and the NICER observatory. Using the optical data, we performed astrometry, photometry, spectroscopy, and power spectral analysis of the optical time series. We present optical Doppler tomography along with X-ray data analysis producing light curves and spectra. Results. We detected SRGA J213151.5+491400 in a high state in 2020 (17.9 mag) that decreased by about 3 mag into a low state (21 mag) in 2021. We find only one significant period using optical photometric time series analysis, which reveals the white dwarf spin (orbital) period to be 0.059710(1) days (85.982 min). The long slit spectroscopy in the high state yields a power-law continuum increasing towards the blue with a prominent He II line along with the Balmer line emissions with no cyclotron humps, which is consistent with a magnetic cataclysmic variable (MCV) nature. Doppler Tomography confirms the polar nature revealing ballistic stream accretion along with magnetic stream during the high state. These characteristics show that the new source is a polar-type MCV source. ART-XC detections yield an X-ray flux of (4.0−7.0) × 10 −12 erg s −1 cm −2 in the high state. eROSITA detects a dominating hot plasma component (kT max > 21 keV in the high state) declining to (4.0−6.0) × 10 −13 erg s −1 cm −2 in 2021 (low state). The NICER data obtained in the low state reveal a two-pole accretor showing a soft X-ray component at (6−7) σ significance with a blackbody temperature of 15−18 eV. A soft X-ray component has never been detected for a polar in the low state before.
ABSTRACT
On 2023 December 12, the star α Orionis will be occulted by asteroid (319) Leona. This represents an extraordinary and unique opportunity to analyse the brightness distribution of ...Betelgeuse’s photosphere with extreme angular resolution by studying light curves from different points on Earth and at different wavelengths. Here we present observations of another occultation by asteroid Leona, on 2023 September 13, whose goal was to determine Leona’s projected shape and size in preparation for the December 12th event and its interpretation. The occultation campaign was highly successful with 25 positive detections from 17 different sites and a near miss. The effective diameter in projected area derived from the positive detections was 66 ± 2 km using an elliptical fit to the instantaneous limb. The body is highly elongated, with dimensions of 79.6 ± 2.2 km × 54.8 ± 1.3 km in its long and short axis, respectively, at occultation time. This result, in combination with dense time series photometry of Leona that we recently obtained, together with archival sparse photometry, allowed us to predict the angular size of the asteroid for the Betelgeuse event and to simulate the expected brightness change. Also, an accurate position coming from the occultation is provided, to improve the orbit of Leona.
In this study we aimed to evaluate the effect of dexmedetomidine and thymoquinone on erythrocyte deformability in lower limb ischaemia-reperfusion (IR) injury in streptozotocin-induced diabetic rats.
...Thirty Wistar albino rats were equally divided into 5 groups (n = 6); randomized control group (Group C), diabetes control group (Group DC), DIR group (Group DIR), DIR group with thymoquinone 25 mg.kg‒1 intraperitoneally (Group DIRT) and Group DIR with dexmedetomidine 100 µg.kg‒1 intraperitoneally (Group DIRD). Erythrocyte packs were prepared from heparinized blood samples and deformability measurements were performed.
IR significantly increased the relative resistance, a marker of erythrocyte deformability when compared to control group (p < 0.05). There were significant differences among the groups in comparisons with ANOVA test (p < 0.0001). Comparisons of the groups DIRD and DIRT revealed similar results (p = 0.824). The values of Group DIR were significantly higher than those of the control, DC, DIRD and DIRT groups (p < 0.0001, p = 0.001, p = 0.004, p = 0.002, respectively). The values of the DC, DIR, DIRD and DIRT groups were significantly higher than those of the control group (p < 0.0001, all).
Erythrocyte deformability may cause more problems in microcirculation. Dexmedetomidine and thymoquinone may be useful in reducing the adverse effects of this type of injury (Fig. 1, Ref. 41).
Ni-based materials are some of the most used hardfacing alloys to improve wear and corrosion resistance for parts functioning under severe conditions. For the current study, a NiCrBSi self-fluxing ...alloy powder with particle size in range of 45-106 μm was employed as feedstock material and deposited onto a steel substrate material using the oxyacetylene thermal spraying process. The as-sprayed components have been subsequently subjected to thermal post-processing in order to increase the adhesion to the substrate and to reduce the inherent porosity of the coatings. Consequently, two types of heating sources were chosen. One of them was the neutral oxyacetylene flame and the second one was based on high frequency currents. The aim of this work was to study the influence of the heat source type of the post treatment on the final characteristics of the coatings. Evaluation of the morphology and microstructure of the developed coatings was performed after the remelting process by means of scanning electron microscopy. Hardness tests were carried out in cross-section complying with the ASTM E384 standard. In both cases, after fusing, the microstructure was refined, with a drastic decrease in porosity. Evaluation of the hardness distribution along the coating cross-section revealed similar values of microhardness.
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