Over the past few years Personal Navigation Systems have become an established tool for route planning, but they are mainly designed for outdoor environments. Indoor navigation is still a challenging ...research area for several reasons: positioning is not very accurate, users can freely move between the interior boundaries of buildings, path network construction process may not be easy and straightforward due to complexity of indoor space configurations. Therefore the creation of a good network is essential for deriving overall connectivity of a building and for representing position of objects within the environment. This paper reviews current approaches to automatic derivation of route graphs for indoor navigation and discusses some of their limitations. Then, it introduces a novel algorithmic strategy for extracting a 3D connectivity graph for indoor navigation based on 2D floor plans.
Abstract
The ExoClock project is an inclusive, integrated, and interactive platform that was developed to monitor the ephemerides of the Ariel targets to increase the mission efficiency. The project ...makes the best use of all available resources, i.e., observations from ground telescopes, midtime values from the literature, and finally, observations from space instruments. Currently, the ExoClock network includes 280 participants with telescopes capable of observing 85% of the currently known Ariel candidate targets. This work includes the results of ∼1600 observations obtained up to 2020 December 31 from the ExoClock network. These data in combination with ∼2350 midtime values collected from the literature are used to update the ephemerides of 180 planets. The analysis shows that 40% of the updated ephemerides will have an impact on future scheduling as either they have a significantly improved precision or they have revealed biases in the old ephemerides. With the new observations, the observing coverage and rate for half of the planets in the sample has been doubled or more. Finally, from a population perspective, we identify that the differences in the 2028 predictions between the old and the new ephemerides have an STD that is double what is expected from Gaussian uncertainties. These findings have implications for planning future observations, where we will need to account for drifts potentially greater than the prediction uncertainties. The updated ephemerides are open and accessible to the wider exoplanet community both from our Open Science Framework repository and our website.
Blazars are active galactic nuclei (AGN) with relativistic jets whose non-thermal radiation is extremely variable on various timescales
. This variability seems mostly random, although some ...quasi-periodic oscillations (QPOs), implying systematic processes, have been reported in blazars and other AGN. QPOs with timescales of days or hours are especially rare
in AGN and their nature is highly debated, explained by emitting plasma moving helically inside the jet
, plasma instabilities
or orbital motion in an accretion disc
. Here we report results of intense optical and γ-ray flux monitoring of BL Lacertae (BL Lac) during a dramatic outburst in 2020 (ref.
). BL Lac, the prototype of a subclass of blazars
, is powered by a 1.7 × 10
M
(ref.
) black hole in an elliptical galaxy (distance = 313 megaparsecs (ref.
)). Our observations show QPOs of optical flux and linear polarization, and γ-ray flux, with cycles as short as approximately 13 h during the highest state of the outburst. The QPO properties match the expectations of current-driven kink instabilities
near a recollimation shock about 5 parsecs (pc) from the black hole in the wake of an apparent superluminal feature moving down the jet. Such a kink is apparent in a microwave Very Long Baseline Array (VLBA) image.
ABSTRACT
In 2021 BL Lacertae underwent an extraordinary activity phase, which was intensively followed by the Whole Earth Blazar Telescope (WEBT) Collaboration. We present the WEBT optical data in ...the BVRI bands acquired at 36 observatories around the world. In mid-2021 the source showed its historical maximum, with R = 11.14. The light curves display many episodes of intraday variability, whose amplitude increases with source brightness, in agreement with a geometrical interpretation of the long-term flux behaviour. This is also supported by the long-term spectral variability, with an almost achromatic trend with brightness. In contrast, short-term variations are found to be strongly chromatic and are ascribed to energetic processes in the jet. We also analyse the optical polarimetric behaviour, finding evidence of a strong correlation between the intrinsic fast variations in flux density and those in polarization degree, with a time delay of about 13 h. This suggests a common physical origin. The overall behaviour of the source can be interpreted as the result of two mechanisms: variability on time-scales greater than several days is likely produced by orientation effects, while either shock waves propagating in the jet, or magnetic reconnection, possibly induced by kink instabilities in the jet, can explain variability on shorter time-scales. The latter scenario could also account for the appearance of quasi-periodic oscillations, with periods from a few days to a few hours, during outbursts, when the jet is more closely aligned with our line of sight and the time-scales are shortened by relativistic effects.
Mammalian immunoglobulin VH families can be grouped into three distinct clans based upon sequence conservation in two of the three framework (FR) intervals. Through replacement/silent site ...substitution analysis, molecular modeling and mathematical evaluation of known immunoglobulin crystal structures, we demonstrate that this conservation reflects preservation of protein sequence and structure. Each clan contains a characteristic FR 1 interval that is solvent‐exposed and structurally separated from the antigen binding site. Families within a clan contain their own unique FR 3 interval that is capable of either influencing the conformation of the antigen binding site or interacting directly with antigen. Our results provide a structural context for theories that address differential use of VH families in the immune response.
Soluble factors produced by human marrow stroma or the murine marrow derived M2-10B4 cell line support ex vivo maintenance for 5-8 weeks of 50% of human long-term culture initiating cells (LTC-IC). ...As the AFT024 cell line supports LTC-IC cultured in contact conditions better than M2-10B4 feeders, we evaluated LTC-IC support in non-contact conditions above AFT024 feeders. We show that only 15% of LTC-IC were maintained for 5 weeks in AFT024 non-contact cultures (n=6, P<0.05). As AFT024-conditioned media added to M2-10B4 non-contact cultures did not inhibit LTC-IC maintenance, AFT024 cells do not secrete factors that inhibit LTC-IC growth. We next characterized heparan sulfate glycosaminoglycans (HS-GAGs) and cytokines produced by AFT024 cells, which are both required for LTC-IC maintenance in M2-10B4 non-contact cultures. The size and extent of O-sulfation of HS-GAGs in AFT024 and M2-10B4 conditioned medium were similar, indicating that absence of hematopoietic specific HS-GAGs is not responsible for the lack of hematopoietic in AFT024 non-contact cultures. Levels of 13 different cytokines secreted in AFT024- and M2-10B4-conditioned medium were similar. However, addition of human SCF, G-CSF, GM-CSF, LIF, MIP-1alpha and IL-6 in concentrations found in human marrow stroma-conditioned medium to AFT024 non-contact cultures increased LTC-IC-maintenance to 72% at 5 weeks. These cytokines improved LTC-IC maintenance in part through interaction with the progenitors and in part, through interaction with the AFT024 feeder. Thus, although LTC-IC maintenance is poor in AFT024 non-contact cultures, addition of human cytokines enhances LTC-IC maintenance in part through indirect effects on the AFT024 feeder. Characterization of known or novel growth factors secreted by AFT024 cells before and after cytokine stimulation may lead to the identification of cytokines that support growth of human hematopoietic stem cells.
The apparent complexity of biology increases as more biomolecular interactions that mediate function become known. We have used NMR spectroscopy and molecular modeling to provide direct evidence that ...tetrameric platelet factor-4 (PF4) and dimeric interleukin-8 (IL8), two members of the CXC chemokine family, readily interact by exchanging subunits and forming heterodimers via extension of their antiparallel β-sheet domains. We further demonstrate using functional assays that PF4/IL8 heterodimerization has a direct and significant consequence on the biological activity of both chemokines. Formation of heterodimers enhances the anti-proliferative effect of PF4 on endothelial cells in culture, as well as the IL8-induced migration of CXCR2 vector-transfected Baf3 cells. These results suggest that CXC chemokine biology, and perhaps cytokine biology in general, may be functionally modulated at the molecular level by formation of heterodimers. This concept, in turn, has implications for designing chemokine/cytokine variants with modified biological properties.
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