We perform high-fidelity simulations of a wide-field telescopic survey searching for Near-Earth Objects (NEOs) larger than 140 m, focusing on the observation and detection model, as well as detection ...efficiency and accuracy. As a test survey, we select the Large Synoptic Survey Telescope (LSST). We use its proposed pointings for a 10-year mission, and model the detection of NEOs in the fields. We discuss individual model parameters for magnitude losses, vignetting, fading, asteroid rotation and colors, fill factor, limiting magnitude, rate of motion, field shape and rotation, and survey patterns. We assess results in terms of the cumulative completeness of the detected population as a function of size and time. Additionally, we examine the sources of modeling uncertainty, and derive the overall NEO population completeness for the baseline LSST survey to be 55 5% for NEOs with absolute magnitude brighter than 22. Including already discovered objects and ongoing surveys, the NEO completeness at the end of the LSST baseline survey should reach ∼77%.
We derived 90% confidence limits (CLs) on the interstellar number density ( ) of interstellar objects (ISOs; comets and asteroids) as a function of the slope of their size-frequency distribution ...(SFD) and limiting absolute magnitude. To account for gravitational focusing, we first generated a quasi-realistic ISO population to from the Sun and propagated it forward in time to generate a steady state population of ISOs with heliocentric distance . We then simulated the detection of the synthetic ISOs using pointing data for each image and average detection efficiencies for each of three contemporary solar system surveys-Pan-STARRS1, the Mt. Lemmon Survey, and the Catalina Sky Survey. These simulations allowed us to determine the surveys' combined ISO detection efficiency under several different but realistic modes of identifying ISOs in the survey data. Some of the synthetic detected ISOs had eccentricities as small as 1.01, which is in the range of the largest eccentricities of several known comets. Our best CL of implies that the expectation that extra-solar systems form like our solar system, eject planetesimals in the same way, and then distribute them throughout the Galaxy, is too simplistic, or that the SFD or behavior of ISOs as they pass through our solar system is far from expectation.
We have conducted a detailed simulation of the ability of the Large Synoptic Survey Telescope (LSST) to link near-Earth and main belt asteroid detections into orbits. The key elements of the study ...were a high-fidelity detection model and the presence of false detections in the form of both statistical noise and difference image artifacts. We employed the Moving Object Processing System (MOPS) to generate tracklets, tracks, and orbits with a realistic detection density for one month of the LSST survey. The main goals of the study were to understand whether (a) the linking of near-Earth objects (NEOs) into orbits can succeed in a realistic survey, (b) the number of false tracks and orbits will be manageable, and (c) the accuracy of linked orbits would be sufficient for automated processing of discoveries and attributions. We found that the overall density of asteroids was more than 5000 per LSST field near opposition on the ecliptic, plus up to 3000 false detections per field in good seeing. We achieved 93.6% NEO linking efficiency for H < 22 on tracks composed of tracklets from at least three distinct nights within a 12 day interval. The derived NEO catalog was comprised of 96% correct linkages. Less than 0.1% of orbits included false detections, and the remainder of false linkages stemmed from main belt confusion, which was an artifact of the short time span of the simulation. The MOPS linking efficiency can be improved by refined attribution of detections to known objects and by improved tuning of the internal kd-tree linking algorithms.
•Statistical analysis of 90% of asteroid CCD data.•Astrometric residuals of sites depend on epoch and magnitude.•New weighting scheme for orbit determination.
We performed a statistical analysis of ...the astrometric errors for the major asteroid surveys. We analyzed the astrometric residuals as a function of observation epoch, observed brightness and rate of motion, finding that astrometric errors are larger for faint observations and some stations improved their astrometric quality over time. Based on this statistical analysis we develop a new weighting scheme to be used when performing asteroid orbit determination. The proposed weights result in ephemeris predictions that can be conservative by a factor as large as 1.5. However, the new scheme is robust with respect to outliers and handles the larger errors for faint detections.
GRB 221009A: The BOAT Burns, Eric; Svinkin, Dmitry; Fenimore, Edward ...
Astrophysical journal. Letters,
03/2023, Letnik:
946, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract GRB 221009A has been referred to as the brightest of all time (BOAT). We investigate the veracity of this statement by comparing it with a half century of prompt gamma-ray burst ...observations. This burst is the brightest ever detected by the measures of peak flux and fluence. Unexpectedly, GRB 221009A has the highest isotropic-equivalent total energy ever identified, while the peak luminosity is at the ∼99th percentile of the known distribution. We explore how such a burst can be powered and discuss potential implications for ultralong and high-redshift gamma-ray bursts. By geometric extrapolation of the total fluence and peak flux distributions, GRB 221009A appears to be a once-in-10,000-year event. Thus, it is almost certainly not the BOAT over all of cosmic history; it may be the brightest gamma-ray burst since human civilization began.
When optimizing blending technologies, the main objective is to determine the right mixing ratio of the raw materials, depending on the different qualities and costs of the raw materials available. ...It can be concluded that research is mainly focused on answering technological questions, and only very few studies take into account the logistics processes related to blending technologies, their design, cost-efficiency, utilization and sustainability including energy efficiency and environmental impact. Based on this fact, within the frame of this research the authors describe a new approach, extending the basic model of blending problems by adding new supply chain efficiency-related components that makes it possible to take logistics parameters related to the raw materials supply (available stocks, batch sizes, transport and storage costs, supply chain structure) into consideration. A mathematical model of this supply chain optimization problem for blending technologies is described including routing and assignment problems in the supply chain, while technological objectives are also taken into consideration as technological objective functions and constraints. The optimization problem described in the model is a problem with non-deterministic polynomial-time hardness (NP-hard), which means that there are no known efficient analytical methods to solve the logistics-related supply chain optimization of blending technologies. As a solution algorithm, the authors have used an evolutive solver and a new metrics, which improved the efficiency of the comparison of distances between solutions of routing problems represented by permutation arrays. The scenario analysis, which focuses on the integrated optimization of technological and logistics problems validates the model and evaluates the solution algorithm and the new metrics. Using the mentioned algorithm, the supply chain processes of the blending technologies can be improved from availability, efficiency, sustainability point of view.
Abstract
We describe enhancements to the
digest
2 software, a short-arc orbit classifier for heliocentric orbits.
Digest
2 is primarily used by the Near-Earth Object (NEO) community to flag newly ...discovered objects for a immediate follow-up and has been a part of NEO discovery process for more than 15 yr. We have updated the solar system population model used to weight the
digest
2 score according to the 2023 catalog of known solar system orbits and extended the list of mean uncertainties for 140 observatory codes. Moreover, we have added Astrometry Data Exchange Standard (ADES) input format support to
digest
2, which provides additional information for the astrometry, such as positional uncertainties for each detection. The
digest
2 code was also extended to read the roving observer astrometric format as well as the ability to compute a new parameter from the provided astrometric uncertainties (
RMS
′
) that can serve as an indicator of in-tracklet curvature when compared with tracklet’s great-circle fit rms. Comparison with the previous version of
digest
2 confirmed the improvement in accuracy of NEO identification and found that using ADES XML input significantly reduces the computation time of the
digest
2.
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•Drug delivery properties of mesoporous silica-gelatin aerogel.•Rapid drug release measured on-line by 1s time resolution.•Characterization of aerogels by NMR cryoporometry, ...diffusiometry and relaxometry.•Relationship between aerogel structure and drug delivery function.
Specific features of a silica-gelatin aerogel (3 wt.% gelatin content) in relation to drug delivery has been studied. It was confirmed that the release of both ibuprofen (IBU) and ketoprofen (KET) is about tenfold faster from loaded silica-gelatin aerogel than from pure silica aerogel, although the two matrices are structurally very similar. The main goal of the study was to understand the mechanistic background of the striking difference between the delivery properties of these closely related porous materials. Hydrated and dispersed silica-gelatin aerogel has been characterized by NMR cryoporometry, diffusiometry and relaxometry. The pore structure of the silica aerogel remains intact when it disintegrates in water. In contrast, dispersed silica-gelatin aerogel develops a strong hydration sphere, which reshapes the pore walls and deforms the pore structure. The drug release kinetics was studied on a few minutes time scale with 1s time resolution. Simultaneous evaluation of all relevant kinetic and structural information confirmed that strong hydration of the silica-gelatin skeleton facilitates the rapid desorption and dissolution of the drugs from the loaded aerogel. Such a driving force is not operative in pure silica aerogels.
Close approaching (or impacting) asteroids can have slow apparent motion in some directions in the sky as they approach Earth. For some objects that approach Earth from east of opposition, the ...induced topocentric motion coming from Earth’s rotation cancels the natural eastward motion in the sky, making the object appear to be almost stationary, This makes discovery difficult. Near-Earth asteroid 2019 OK passed within about 70000 km of Earth on 2019 July 25.06. It evaded discovery inbound, and despite its ∼100 m size and approaching from the nighttime side of Earth, was first seen only about 24 h before closest approach. The reasons why various surveys did not detect it are analyzed. It is compared to a range of synthetic impactors and the appearance of impactors coming from various directions in the nighttime sky is discussed. 2019 OK appeared to be almost stationary, and as a result was not detected as a moving object. Some impacting objects approaching from east of opposition will likely have similar slow motion to 2019 OK. Detection of slow moving nearby objects is a new, unrecognized challenge for Near-Earth Object surveys.
•Asteroids that may impact Earth can have slow skyplane velocity.•Topocentric motion can cancel slow eastward motion of an impacting asteroid, making it appear stationary.•Slow-moving asteroids are challenging for Near-Earth Object surveys to discover.
Naturally occurring and anthropogenic petroleum hydrocarbons are potential carbon sources for many bacteria. The AlkB-related alkane hydroxylases, which are integral membrane non-heme iron enzymes, ...play a key role in the microbial degradation of many of these hydrocarbons. Several members of the genus Rhodococcus are well-known alkane degraders and are known to harbor multiple alkB genes encoding for different alkane 1-monooxygenases. In the present study, 48 Rhodococcus strains, representing 35 species of the genus, were investigated to find out whether there was a dominant type of alkB gene widespread among species of the genus that could be used as a phylogenetic marker. Phylogenetic analysis of rhodococcal alkB gene sequences indicated that a certain type of alkB gene was present in almost every member of the genus Rhodococcus. These alkB genes were common in a unique nucleotide sequence stretch absent from other types of rhodococcal alkB genes that encoded a conserved amino acid motif: WLG(I/V/L)D(G/D)GL. The sequence identity of the targeted alkB gene in Rhodococcus ranged from 78.5 to 99.2% and showed higher nucleotide sequence variation at the inter-species level compared to the 16S rRNA gene (93.9–99.8%). The results indicated that the alkB gene type investigated might be applicable for: (i) differentiating closely related Rhodococcus species, (ii) properly assigning environmental isolates to existing Rhodococcus species, and finally (iii) assessing whether a new Rhodococcus isolate represents a novel species of the genus.
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