Using solar panels is one of the cleanest ways to generate electricity ever created by mankind. The efficiency of rapidly expanding solar panels decreases during their lifetime for several reasons, ...such as photodegradation, hot spots, potentially induced degradation, etc. Dirt and debris accumulation on the surface of the solar panels can also significantly contribute to their performance degradation due to the diminishing of the solar radiation reaching their active surfaces. Numerous degradation mitigation methods are cited in the literature. This article briefly outlines these basic measures.
In recent years, there has been considerable interest in icariin (ICA) and its derivates, icariside II (ICS) and icaritin (ICT), due to their wide range of potential applications in preventing ...cancer, cardiovascular disease, osteoporosis, delaying the effects of Alzheimer’s disease, treating erectile dysfunction, etc. However, their poor water solubility and membrane permeability, resulting in low bioavailability, dampens their potential beneficial effects. In this regard, several strategies have been developed, such as pharmaceutical technologies, structural transformations, and absorption enhancers. All these strategies manage to improve the bioavailability of the above-mentioned flavonoids, thus increasing their concentration in the desired places. This paper focuses on gathering the latest knowledge on strategies to improve bioavailability for enhancing the efficacy of icariin, icariside II, and icaritin. We conclude that there is an opportunity for many further improvements in this field. To the best of our knowledge, no such review articles scoping the bioavailability improvement of icariin and its derivates have been published to date. Therefore, this paper can be a good starting point for all those who want to deepen their understanding of the field.
Abstract
The K2 mission of the Kepler Space Telescope allowed the observations of light curves of small solar system bodies throughout the whole solar system. In this paper, we present the results of ...a collection of K2 trans-Neptunian object observations between campaigns C03 (2014 November–2015 February) and C19 (2018 August–September), which includes 66 targets. Due to the faintness of our targets, the detectability rate of a light-curve period is ∼56%, notably lower than in the case of other small-body populations, like Hildas or Jovian Trojans. We managed to obtain light-curve periods with an acceptable confidence for 37 targets; the majority of these cases are new identifications. We were able to give light-curve amplitude upper limits for the other 29 targets. Several of the newly detected light-curve periods are longer than ∼24 hr, in many cases close to ∼80 hr; i.e., these targets are slow rotators. This relative abundance of slowly rotating objects is similar to that observed among Hildas, Jovian Trojans, and Centaurs in the K2 mission, as well as among main belt asteroids measured with the TESS space telescope. Trans-Neptunian objects show notably higher light-curve amplitudes at large (
D
≳ 300 km) sizes than found among large main belt asteroids, in contrast to the general expectation that due to their lower compressive strength, they reach hydrostatic equilibrium at smaller sizes than their inner solar system counterparts.
Abstract
Various properties of Jovian Trojan asteroids such as composition, rotation periods, and photometric amplitudes, or the rate of binarity in the population, can provide information and ...constraints on the evolution of the group and of the solar system itself. Here we present new photometric properties of 45 Jovian Trojans from the K2 mission of the Kepler space telescope, and present phase-folded light curves for 44 targets, including (11351) Leucus, one of the targets of the Lucy mission. We extend our sample to 101 asteroids with previous K2 Trojan measurements, then compare their combined amplitude and frequency distributions to other ground-based and space data. We show that there is a dichotomy in the periods of Trojans with a separation at ∼100 hr. We find that 25% of the sample are slow rotators (
P
≥ 30 hr), an excess that can be attributed to binary objects. We also show that 32 systems can be classified as potential detached binary systems. Finally, we calculate density and rotation constraints for the asteroids. Both the spin barrier and fits to strengthless ellipsoid models indicate low densities and thus compositions similar to populations of comets and trans-Neptunian objects throughout the sample. This supports the scenario of outer solar system origin for Jovian Trojans.
Hilda asteroids orbit at the outer edge, or just outside of the Main Belt, occupying the 2:3 mean motion resonance with Jupiter. It is known that the group shows a mixed taxonomy that suggests the ...mixed origin of Hilda members, having migrated to the current orbit both from the outer Main Belt and from the Trojans swarms. But there are still few observations for comparative studies to help us understand the Hilda group in deeper detail. We identified 125 individual light curves of Hilda asteroids observed by the K2 mission. We found that despite of the mixed taxonomies, the Hilda group highly resembles the Trojans in the distribution of rotation periods and amplitudes, and even the LR group (mostly C- and X-type) Hildas follow this rule. Contrary to the Main Belt, the Hilda group lacks the very fast rotators. The ratio of extremely slow rotators (P > 100 hr) is a surprising 18%, which is unique in the solar system. The occurrence rate of asteroids with multiple periods (4%) and asteroids with three maxima in the light curves (5%) can be signs of a high rate of binarity, which we can estimate as 25% within the Hilda group.
ABSTRACT We present the first comprehensive thermal and rotational analysis of the second most distant trans-Neptunian object (TNOs) (225088) 2007 OR10. We combined optical light curves provided by ...the Kepler Space Telescope-K2 extended mission and thermal infrared data provided by the Herschel Space Observatory. We found that (225088) 2007 OR10 is likely to be larger and darker than derived by earlier studies: we obtained a diameter of d = 1535 − 225 + 75 km which places (225088) 2007 OR10 in the biggest top three TNOs. The corresponding visual geometric albedo is p V = 0.089 − 0.009 + 0.031 . The light-curve analysis revealed a slow rotation rate of Prot = 44.81 0.37 hr, superseded by very few objects. The most likely light-curve solution is double-peaked with a slight asymmetry; however, we cannot safely rule out the possibility of having a rotation period of Prot = 22.40 0.18 hr, which corresponds to a single-peaked solution. Due to the size and slow rotation, the shape of the object should be a MacLaurin ellipsoid, so the light variation should be caused by surface inhomogeneities. Its newly derived larger diameter also implies larger surface gravity and a more likely retention of volatiles-CH4, CO, and N2-on the surface.
ABSTRACT
There is a lack of exoplanets with sizes similar to Neptune orbiting their host stars with periods ≲3 d – hence the name ‘sub-Jovian/Neptune desert’. Recently, several exoplanets have been ...confirmed to reside in the desert, transforming it into a ‘savanna’ with several ‘giraffe’ planets (such as LTT 9779 b and TOI-674 b). The most prominent scenarios put forward for the explanation of the formation of the desert are related to the stellar irradiation destroying the primary atmosphere of certain specific exoplanets. We aim to present three targets (LTT 9779 b, TOI-674 b, and WASP-156 b) that, when observed at wide wavelength ranges in infrared (IR), could prove the presence of these processes, and therefore improve the theories of planetary formation/evolution. We simulate and analyse realistic light curves of the selected exoplanets with PLATO/N-CAM and the three narrow-band filters of Ariel (VISPhot, FGS1, and FGS2) based on TESS observations of these targets. We improved the precision of the transit parameters of the three considered planets from the TESS data. We find that the combination of the three narrow-band filters of Ariel can yield an inner precision of ${\lesssim}1.1\ \hbox{per cent}$ for the planetary radii. Data from the three telescopes together will span decades, allowing the monitoring of changes in the planetary atmosphere through radius measurements. The three selected ‘giraffe’ planets can be golden targets for Ariel, whereby the loss of planetary mass due to stellar irradiation could be studied with high precision, multiwavelength (spectro-)photometry.
Abstract
Proper photometric data are challenging to obtain in the K2 mission of the Kepler space telescope due to strong systematics caused by the two-wheel-mode operation. It is especially true for ...variable stars wherein physical phenomena occur on timescales similar to the instrumental signals. We originally developed a method with the aim to extend the photometric aperture to be able to compensate the motion of the telescope which we named Extended Aperture Photometry (EAP). Here we present the outline of the automatized version of the EAP method, an open-source pipeline called
autoEAP
. We compare the light curve products to other photometric solutions for examples chosen from high-amplitude variable stars. In addition to the photometry, we developed a new detrending method, which is based on phase dispersion minimization and is able to eliminate long-term instrumental signals for periodic variable stars.
The unprecedented photometric precision along with the quasi-continuous sampling provided by the
Kepler
space telescope revealed new and unpredicted phenomena that reformed and invigorated RR Lyrae ...star research. The discovery of period doubling and the wealth of low-amplitude modes enlightened the complexity of the pulsation behavior and guided us toward nonlinear and nonradial studies. Searching and providing theoretical explanation for these newly found phenomena became a central question, as well as understanding their connection to the oldest enigma of RR Lyrae stars, the Blazhko effect. We attempt to summarize the highest impact RR Lyrae results based on or inspired by the data of the
Kepler
space telescope both from the nominal and from the K2 missions. Besides the three most intriguing topics, the period doubling, the low-amplitude modes, and the Blazhko effect, we also discuss the challenges of
Kepler
photometry that played a crucial role in the results. The secrets of these amazing variables, uncovered by
Kepler
, keep the theoretical, ground-based, and space-based research inspired in the post-
Kepler
era, since light variation of RR Lyrae stars is still not completely understood.
Abstract
In this paper, we describe a project we initiated to investigate individual pixels in downloaded Kepler apertures in order to find objects in the background of the main targets with variable ...brightness. In the first paper of this series, we discovered and investigated 547 short-period eclipsing binaries. Here we present the independent discovery of 26 new RR Lyrae stars in the Kepler background pixels obtained during the primary mission and provide continuous and precise photometry for these objects. Twenty-one of these stars were already noted by the Gaia or the Pan-STARRS survey. This new population of dominantly faint and distant RR Lyrae stars increases by 50% and complements nicely the 52 already known main target RR Lyrae stars in the original Kepler field. Despite their faintness, the four-year quasi-uninterrupted light curves of these stars allow an unprecedented view of these faint halo objects. We present an analysis of the light curves of the new RR Lyrae sample, verify their classification using Fourier parameters, and discuss the properties of these newly found pulsating variable stars. Most notably, this is the first time that such faint RR Lyrae stars have been investigated with the help of a photometric data set with outstanding cadence and precision. Interestingly, these objects share the properties of their brighter siblings in terms of subclass characteristics, additional mode content, and modulation occurrence rates.
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