ABSTRACT
The Taurid Meteoroid Complex (TMC) is a broad stream of meteoroids that produces several annual meteor showers on Earth. If the linkage between these showers and 2P/Encke is at the centre of ...most TMC models, the small size and low activity of the comet suggest that 2P/Encke is not the unique parent body of the Taurids. Here, we simulate the formation of the TMC from 2P/Encke and several NEAs. In total, we explored more than a hundred stream formation scenarios using clones of 2P/Encke. Each modelled stream was integrated and compared with present-day Taurid observations. As previously reported, we find that even slight variations of 2P/Encke’s orbit modifie considerably the characteristics of the simulated showers. Most of the comet’s clones, including the nominal one, appear to reproduce the radiant structure of the Taurid meteors but do not match the observed time and duration of the showers. However, the radiants and timing of most Taurid showers are well reproduced by a particular clone of the comet. Our analysis thus suggest that with this specific dynamical history, 2P/Encke is the sole parent of the four major TMC showers that have ages from 7 to 21 ka. Our modelling also predicts that the 2022 Taurid Resonant Swarm return will be comparable in strength to the 1998, 2005, and 2015 returns. While purely dynamical models of Encke’s orbit – limited by chaos – may fail to reveal the comet’s origin, its meteor showers may provide the trail of breadcrumbs needed to backtrack our way out of the labyrinth.
ABSTRACT
We provide an overview of the observational properties of the four major Taurid showers, namely the Northern and Southern Taurids (#017 NTA and #002 STA), the β Taurids (#173 BTA), and the ζ ...Perseids (#172 ZPE). Analysing more than two decades of meteor observations from visual, optical, and radar measurements, we present the Taurids average activity, annual variations in strength, radiant drift, and orbital variations as a function of solar longitude and particle size. The Taurid showers are detected over several weeks in the spring and autumn, but their annual activity level is generally low (less than 15 visual meteors per hour). We find the STA to be pre-dominant in autumn, while its twin, the ZPE, dominates over the BTA in spring. Due to their long duration, the position of each shower’s radiant and orbital elements are variable with time. Optical measurements have previously recorded enhanced STA activity and increased fireball rates caused by the return of a swarm of meteoroids trapped in the 7:2 mean motion resonance with Jupiter. However, we find no presence of the swarm in radar data, suggesting that small meteoroids are removed from the resonance faster than fireball-producing meteoroids. We also find the STA to be enriched in smaller particles early in their activity period. The differences we identify in our analysis between the showers at different particle sizes provide strong observational constraints to future dynamical modelling of the Taurid Meteoroid Complex.
Context.
We present a new numerical model of the
η
-Aquariid and Orionid meteor showers.
Aims.
The model investigates the origin, variability, and age of the
η
-Aquariid and Orionid apparitions from ...1985 to the present day in order to forecast their activity over the next several decades.
Methods.
Through the numerical integration of millions of simulated meteoroids and a custom-made particle weighting scheme, we model the characteristics of every
η
-Aquariid and Orionid apparition between 1985 and 2050. The modeled showers are calibrated using 35 yr of meteor observations, including the shower activity profiles and interannual variability.
Results.
Our model reproduces the general characteristics of the present-day
η
-Aquariids and part of the Orionid activity. Simulations suggest that the age of the
η
-Aquariids somewhat exceeds 5000 yr, while a greater fraction of the Orionids is composed of older material. The 1:6 mean motion resonance with Jupiter plays a major role in generating some (but not all) Halleyid stream outbursts. We find consistent evidence for a periodicity of 11.8 yr in both the observations and modeled maximum meteor rates for the Orionids. Weaker evidence of a 10.7 yr period in the peak activity for the
η
-Aquariids needs to be investigated with future meteor observations. The extension of our model to future years predicts no significant Orionid outbursts through 2050 and four significant
η
-Aquariid outbursts, in 2023, 2024, 2045, and 2046.
Context.
Several authors predicted an outburst of the Draconid meteor shower in 2018, but with an uncertain level of activity.
Aims.
Optical meteor observations were used to derive the population and ...mass indices, flux, and radiant positions of Draconid meteors.
Methods.
We performed 90 min of multi-station observations after the predicted peak of activity using highly sensitive Electron Multiplying Charge Coupled Device cameras. The data calibration is discussed in detail. A novel maximum likelihood estimation method was developed to compute the population and mass index with robust error estimation. We applied the method to observed Draconids and used the values to derive the flux. Meteor trajectories were computed and compared to predicted radiant positions from meteoroid ejection models.
Results.
We find a mass index of 1.74 ± 0.18 in the 30 min bin after the predicted peak, and 2.32 ± 0.27 in the subsequent 60 min. The location and the dispersion of the radiant are a good match to modeled values, but there is an offset of 0.4° in solar longitude.
Aims.
We present a multi-instrumental, multidecadal analysis of the activity of the Eta-Aquariid and Orionid meteor showers for the purpose of constraining models of 1P/Halley’s meteoroid streams.
...Methods.
The interannual variability of the showers’ peak activity and period of duration is investigated through the compilation of published visual and radar observations prior to 1985 and more recent measurements reported in the International Meteor Organization (IMO) Visual Meteor DataBase, by the IMO Video Meteor Network and by the Canadian Meteor Orbit Radar (CMOR). These techniques probe the range of meteoroid masses from submilligrams to grams. The
η
-Aquariids and Orionids activity duration, shape, maximum zenithal hourly rates values, and the solar longitude of annual peaks since 1985 are analyzed. When available, annual activity profiles recorded by each detection network were measured and are compared.
Results.
Observations from the three detection methods show generally good agreement in the showers’ shape, activity levels, and annual intensity variations. Both showers display several activity peaks of variable location and strength with time. The
η
-Aquariids are usually two to three times stronger than the Orionids, but the two showers display occasional outbursts with peaks two to four times their usual activity level. CMOR observations since 2002 seem to support the existence of an ~12 yr cycle in Orionids activity variations; however, additional and longer term radar and optical observations of the shower are required to confirm such periodicity.
ABSTRACT
The goal of this work is to determine if the dynamics of individual Taurid Complex (TC) objects are consistent with the formation of the complex via fragmentation of a larger body, or if the ...current orbital affinities between the TC members result from other dynamical processes. To this end, the orbital similarity through the time of comet 2P/Encke, 51 near-Earth asteroids (NEAs), and 16 Taurid fireballs was explored. Clones of each body were numerically simulated backwards in time, and epochs when significant fractions of the clones of any two bodies approached each other with both a low Minimum Orbit Intersection Distance and small relative velocity were identified. Only 12 pairs of bodies in our sample show such an association in the past 20 000 yr, primarily circa 3200 BCE. These include 2P/Encke and NEAs 2004 TG10, 2005 TF50, 2005 UR, 2015 TX24, and several Southern Taurid fireballs. We find this orbital convergence to be compatible with the fragmentation of a large parent body 5000–6000 yr ago, resulting in the separation of 2P/Encke and several NEAs associated with the TC, as well as some larger meteoroids now recorded in the Taurid stream. However, the influence of purely dynamical processes may offer an alternative explanation for this orbital rapprochement without requiring a common origin between these objects. In order to discriminate between these two hypotheses, future spectral surveys of the TC asteroids are required.
The existence of multiple forms of malnutrition is a growing problem in developing countries. Children living in the Eastern Cape have a relatively high prevalence of cardiovascular disease (CVD) ...risk factors and food insecurity, suggesting the possibility of the several coexisting forms of malnutrition. Due to the negative long-term consequences of undernutrition, overnutrition and, to a greater extent, a combination of both, it is important for this issue to be identified early in children and addressed.
This study was undertaken to investigate the prevalence of the different forms of malnutrition in children living in the Eastern Cape province.
Secondary analysis of a cross-sectional sample of 237 school-aged children, aged 6-18 years, in the Eastern Cape province of South Africa was conducted. The variables included in the analysis were the demographic data, anthropometric data and biochemical data, specifically blood profiles related to micronutrient deficiencies and CVD risk factors. Fisher's exact test was used to compare the prevalence rates of several coexisting forms of malnutrition in the children. All data analysis was conducted in R version 4.0.3 and statistical significance was set at 0.05.
In children with overweight/obesity, 13.6% had a micronutrient deficiency, while 37.71% of the children within the normal weight range had coexisting micronutrient deficiencies and CVD risk factors. The prevalence of folate deficiency was 73.0%, iron deficiency 6.3%, and hyperglycaemia was at 10.6%. Fisher's exact test was used to compare the prevalence rates between genders and no statistically significant differences were observed.
Further research is needed to understand the relatively high prevalence of CVD risk factors in these children within the normal weight range and to investigate how dietary intake contributes to the overall double burden of malnutrition in children.
In the fields of psychology and psychiatry, the use of the terms impulsivity, sensation-seeking and ordalie to refer to risk-taking behaviors can sometimes be confusing.
The objective of this study ...was to establish a clinical definition of the concepts of ordalie, sensation-seeking and impulsivity, in order to analyze the similarities and differences between these concepts.
We prioritized literature review articles with or without meta-analysis from the Medline database and supplemented with the Google-Scholar database. The articles were included in this review if their objectives were in line with ours. The research was conducted in November 2018.
Twenty-seven articles were selected. There are similarities in the clinical definitions of these concepts with measurable heterogeneous constructions, and an exacerbation in adolescence for engagement in harmful behaviors, but there are also nuances that highlight their differences.
We were able to describe areas of divergence and convergence between these three concepts but not to establish a quantitative diagram of the areas of divergence and convergence. It would seem that the coexistence of sensation-seeking and impulsivity in the same individual could explain that individual's involvement in ordalique behaviors. Further studies approaching this hypothesis would seem useful in terms of preventing risk-taking behaviors such as addictive behaviors.
Control over the average length of single-walled carbon nanotubes (SWNTs) in suspension is of critical importance to characterizing and developing flexible, transparent thin films that use ...percolative transport to achieve reproducibility in electronic properties. This paper demonstrates how the average length of SWNTs in aqueous suspensions can be controlled by the conditions used to form (sonication) and purify (low-G centrifugation) the dispersions. The effect of ultrasonic probe sonication, which was used to disperse SWNT bundles into suspension, on the length and extent of defects on the nanotubes was investigated via atomic force microscopy (AFM) and confocal Raman spectroscopy, respectively. Quantitative information about the suspension concentration and the effect of sonication power on unbundling the SWNTs was obtained via UV−vis and near-IR spectroscopy, respectively. To obtain a clear understanding of the effect of sonication power on SWNT suspensions, repeated low-G centrifugation cycles were used to remove impurities such as bundles of SWNTs, amorphous carbon, and catalyst nanoparticles. This nonoxidizing purification method, which was performed prior to all analyses, allows direct determination of the effect of sonication power on defect formation.
Numerous systemic diseases (vasculitis, connective tissue disease or sarcoidosis) can display an involvement of the perianal skin, the rectum and/or the anus. Such knowledge is important in order to ...treat these complications specifically when possible. Lesions of the anorectum arising from systemic diseases can sometimes cause perforations in the peritoneal cavity (if concerning the higher portion of the rectum) and/or fistulization to the anal margin. Differential diagnosis, mostly infectious or inflammatory (Crohn's disease) must be ruled out in every case. Other systemic diseases can display specific manifestations as this is the case in scleroderma which can lead to anal incontinence. Despite the relative rarity of these manifestations, their ignorance would forbid global management of these complex diseases. It should thus be detected in each consultation and a regular follow-up must be provided with a proctologist and/or a gastroenterologist when needed.
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