F Ring Core Stability: Corotation Resonance Plus Antiresonance

The decades-or-longer stability of the narrow F Ring core in a sea of orbital chaos appears to be due to an unusual combination of traditional corotation resonance and a novel kind of "antiresonance". At a series of specific locations in the F Ring region, apse precession between synodic encounters with Prometheus allows semimajor axis perturbations to promptly cancel before significant orbital period changes can occur. This cancellation fails for particles that encounter Prometheus when it is near its apoapse, especially during periods of antialignment of its apse with that of the F Ring. At these times, the strength of the semimajor axis perturbation is large (tens of km) and highly nonsinusoidal in encounter longitude, making it impossible to cancel promptly on a subsequent encounter and leading to chaotic orbital diffusion. Only particles that consistently encounter Prometheus away from its apoapse can use antiresonance to maintain stable orbits, implying that the true mean motion nF of the stable core must be defined by a corotational resonance of the form nF = nP(-kappa)P/m, where (nP, kappaP) are Prometheus' mean motion and epicycle frequency. To test this hypothesis we used the fact that Cassini RSS occultations only sporadically detect a "massive" F Ring core, composed of several-cm-and-larger particles. We regressed the inertial longitudes of 24 Cassini RSS (and VGR) detections and 43 nondetections to a common epoch, using a comb of candidate nP, and then folded them modulo the anticipated m-number of the corotational resonance (Prometheus m = 110 outer CER), to see if clustering appears. We find the "true F Ring core" is actually arranged in a series of short longitudinal arcs separated by nearly empty longitudes, orbiting at a well determined semimajor axis of 140222.4 km (from 2005-2012 at least). Small particles seen by imaging and stellar occultations spread quickly in azimuth and obscure this clumpy structure. Small chaotic variations in the mean motion and/or apse longitude of Prometheus quickly become manifest in the F Ring core, and we suggest that the core must adapt to these changes for the F Ring to maintain stability over timescales of decades and longe

Biological characteristics of Cadra cautella (Lep.: Pyralidae) on different varieties of stored date palm fruit of Iran

The postharvest pests, including the dried fruit moth Cadra cautella Walker, are important limiting factors in the exportation of dates. The biology of C. cautella, its survivorship, developmental time, fecundity, oviposition, post oviposition period, as well as longevity of the adults were studied on four date palm varieties of Zahedi, Piarom, Rabbi, and Deyri under laboratory conditions in Iran. The experiments were carried out at constant temperature room (29 ± 1 °C, 60 ± 5% RH and photoperiod 16L: 8D hrs.). The highest survivorship of egg and larval stages was recorded 92.66%, 85.89% on Zahedi and 100% for pupal stage on Rabbi. The shortest larval period was 32.93 ± 1.41 days and 33.37 ± 1.87 days on Deyri and Zahedi respectively. The shortest total development time for males from egg to adult was 40.91 ± 1.15 days and 40.97 ± 1.59 days on Zahedi and Deyri respectively and for females was 43.76 ± 2.47 days on Deyri. The longest total development time for males was 47.61 ± 1.50 days on Piarom and for female was 55.88 ± 2.31 and 55.37 ± 3.87 days on Piarom and Rabbi respectively. The highest (247.00 ± 8.53 eggs per female) and lowest (147.40 ± 12.06 eggs per female) fecundity occurred on Zahedi and Piarom, respectively. The date palm varieties Zahedi, Deyri, Rabbi and Piarom are found to be on preferrence order for C. cautella. The results of this study would be useful for planning pest management strategies in date palm fruit storages

The Rings of Saturn

One could become an expert on Saturn's iconic rings pretty easily in the early 1970s, as very little was known about them beyond the distinction between the A, B, and C rings, and the Cassini Division or "gap" between rings A and B (Alexander, 1962; Bobrov, 1970). Water ice was discovered spectroscopically on the ring particle surfaces, and radar and microwave emission observations proved that the particles must be centimeters to meters in size, consisting primarily, not just superficially, of water ice (Pollack, 1975). While a 2:1 orbital resonance with Mimas had long been suspected of having something to do with the Cassini Division, computers of the time were unable to model the subtle dynamical effects that we now know to dominate ring structure. This innocent state of affairs was exploded by the Voyager 1 and 2 encounters in 1980 and 1981. Spectacular images revealed filigree structure and odd regional color variations, and exquisitely detailed radial profiles of fluctuating particle abundance were obtained from the first stellar and radio occultations, having resolution almost at the scale of single particles. Voyager-era understanding was reviewed by Cuzzi et al. (1984) and Esposito et al. (1984). While the Voyager data kept ring scientists busy for decades, planning which led to the monumentally successful NASA-ESA-ASI Cassini mission, which arrived in 2004, had been under way even before Voyager got to Saturn. A review of pre-Cassini knowledge of Saturn's Rings can be found in Orton et al. (2009). This chapter will build on recent topical and process-specific reviews that treat the gamut of ring phenomena and its underlying physics in considerable detail (Colwell et al., 2009; Cuzzi et al., 2009; Horányi et al., 2009; Schmidt et al., 2009; Esposito, 2010; Tiscareno, 2013b; Esposito, 2014). We will follow and extend the general organization of Cuzzi et al. (2010), the most recent general discussion of Saturn's rings. For brevity and the benefit of the reader, we will frequently refer to the above review articles instead of directly to the primary literature they discuss. We will focus on new work since 2010, within a general context, and will connect our high-level discussions with more detailed chapters in this volume

Spatio-Temporal Pattern of Saturn's Equatorial Oscillation

Recent ground-based and Cassini CIRS thermal-infrared data have characterized the spatial and temporal characteristics of an equatorial oscillation in the middle atmosphere of Saturn above the 100-mbar level. The CIRS data [I] indicated a pattern of warm and cold anomalies near the equator, stacked vertically in alternating fashion. The ground-based observations s2, although not having the altitude range or vertical resolution of the CIRS observations, covered several years and indicated an oscillation cycle of approx.15 years, roughly half of Saturn's year. In Earth's middle atmosphere, both the quasi-biennial (approx.26 months) and semi-annual equatorial oscillations have been extensively observed and studied (see e.g., [3]), These exhibit a pattern of alternating warmer and cooler zonal-mean temperatures with altitude, relative to those at subtropical latitudes. Consistent with the thermal wind equation, this is also associated with an alternating pattern of westerly and easterly zonal winds. Moreover, the pattern of winds and temperatures descends with time. Momentum deposition by damped vertically propagating waves is thought to play a key role m forcing both types of oscillation, and it can plausibly account for the descent. Here we report the direct observation of this descent in Saturn's equatorial atmosphere from Cassini radio occultation soundings in 2005 and 2009. The retrieved temperatures are consistent with a descent of 0.7 x the pressure scale height. The descent rate is related to the magnitude of the wave forcing, radiative damping, and induced meridional circulations. We discuss possible implications

Antenne Microruban Miniature Ultra Large Bande ULB pour Imagerie Micro-onde

Ce travail consiste à concevoir une antenne répondant aux exigences des systèmes Ultra Large Bande ULB. Ces derniers sont très présents dans différentes applications, à titre non exhaustif, nous citerons l’imagerie médicale microonde, les communications sans fil, les systèmes de positionnement et systèmes Radars. Pour cela, l’antenne doit présenter de bonnes performances sur la bande de fréquence 3.1- 10.6 GHz, spectre alloué à l’ULB par la commission FCC (Federal Communications Commission). Nous proposons une antenne imprimée miniature de forme rectangulaire qui satisfait les caractéristiques ULB en termes de bande passante et de coefficient de réflexion. Cette antenne est destinée à un système de détection de tumeurs malignes par imagerie microondes. Nous exploitons certaines techniques de miniaturisation et d’élargissement de la bande passante afin de réaliser notre objectif

Saturn's Equatorial Oscillation: Evidence of Descending Thermal Structure from Cassini Radio Occultations

Ground-based and Cassini CIRS thermal-infrared data have characterized the spatial and temporal characteristics of an equatorial oscillation in Saturn's middle atmosphere above the 100-mbar level. The CIRS data indicate a vertical pattern of alternating warm and cold anomalies at the equator. From the thermal wind equation this implies a concomitant reversal of zonal winds with attitude, relative to the cloud-top winds, with peak-to-peak amplitude approximately 200 meters per second. The ground-based observations do not having the altitude range or vertical resolution of the CIRS observations, but they cover several years and indicate an oscillation cycle of 1 years, roughly half of Saturn's year. Equatorial oscillations in Earth's middle atmosphere have primarily exhibited either quasi-biennial or semi-annual "periodicities," and both types have been extensively observed and modeled. They exhibit a vertical pattern of alternating warmer and cooler zonal-mean temperatures and zonal winds analogous to that described above for Saturn. Moreover, the pattern of winds and temperatures descends with time. Momentum deposition by damped vertically propagating easterly and westerly waves is thought to play a key role in forcing both types of oscillation, and it can plausibly account for the descent. Here we report the direct observation of this descent in Saturn's equatorial atmosphere from Cassini radio occultation soundings in 2005 and 2009. The retrieved temperatures are consistent with a descent of 0.6 x the pressure scale height over this time period. The descent rate is related to the magnitude of the wave forcing, radiative damping, and induced meridional circulations. A simple calculation implies that vertical wave fluxes of zonal momentum approximately 0.05 square meters per square second could account for the observed vertical descent on Saturn, which is comparable to the magnitude of the wave fluxes associated with the terrestrial quasi-biennial oscillation

Association between periodontitis and severity of COVID-19 infection: A case–control study

Aim: COVID-19 is associated with an exacerbated inflammatory response that can result in fatal outcomes. Systemic inflammation is also a main characteristic of periodontitis. Therefore, we investigated the association of periodontitis with COVID-19 complications. Materials and Methods: A case–control study was performed using the national electronic health records of the State of Qatar between February and July 2020. Cases were defined as patients who suffered COVID-19 complications (death, ICU admissions or assisted ventilation), and controls were COVID-19 patients discharged without major complications. Periodontal conditions were assessed using dental radiographs from the same database. Associations between periodontitis and COVID 19 complications were analysed using logistic regression models adjusted for demographic, medical and behaviour factors. Results: In total, 568 patients were included. After adjusting for potential confounders, periodontitis was associated with COVID-19 complication including death (OR = 8.81, 95% CI 1.00–77.7), ICU admission (OR = 3.54, 95% CI 1.39–9.05) and need for assisted ventilation (OR = 4.57, 95% CI 1.19–17.4). Similarly, blood levels of white blood cells, D-dimer and C Reactive Protein were significantly higher in COVID-19 patients with periodontitis. Conclusion: Periodontitis was associated with higher risk of ICU admission, need for assisted ventilation and death of COVID-19 patients, and with increased blood levels of biomarkers linked to worse disease outcomes