Abstract The chemical composition of an extrasolar planet is fundamental to its formation, evolution, and habitability. In this study, we explore a new way to measure the chemical composition of the ...building blocks of extrasolar planets by measuring the gas composition of the disrupted planetesimals around white dwarf stars. As a first attempt, we used the photoionization code Cloudy to model the circumstellar gas emission around white dwarf Gaia J0611−6931 under some simplified assumptions. We found that most of the emission lines are saturated, and the line ratios approach the ratios of thermal emission; therefore, only lower limits to the number density can be derived. Silicon is the best-constrained element in the circumstellar gas, and we derived a lower limit of 10 10.3 cm −3 . In addition, we placed a lower limit on the total amount of gas to be 1.8 × 10 19 g. Further study is needed to better constrain the parameters of the gas disk and connect it to other white dwarfs with circumstellar gas absorption.
The No Free Lunch Theorem tells us that no algorithm can beat other algorithms on all types of problems. The algorithm selection structure is proposed to select the most suitable algorithm from a set ...of algorithms for an unknown optimization problem. This paper introduces an innovative algorithm selection approach called the CNN-HT, which is a two-stage algorithm selection framework. In the first stage, a Convolutional Neural Network (CNN) is employed to classify problems. In the second stage, the Hypothesis Testing (HT) technique is used to suggest the best-performing algorithm based on the statistical analysis of the performance metric of algorithms that address various problem categories. The two-stage approach can adapt to different algorithm combinations without the need to retrain the entire model, and modifications can be made in the second stage only, which is an improvement of one-stage approaches. To provide a more general structure for the classification model, we adopt Exploratory Landscape Analysis (ELA) features of the problem as input and utilize feature selection techniques to reduce the redundant ones. In problem classification, the average accuracy of classifying problems using CNN is 96%, which demonstrates the advantages of CNN compared to Random Forest and Support Vector Machines. After feature selection, the accuracy increases to 98.8%, further improving the classification performance while reducing the computational cost. This demonstrates the effectiveness of the first stage of the CNN-HT method, which provides a basis for algorithm selection. In the experiments, CNN-HT shows the advantages of the second stage algorithm as well as good performance with better average rankings in different algorithm combinations compared to the individual algorithms and another algorithm combination approach.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
WD 1145+017 is a unique white dwarf system that has a heavily polluted atmosphere, an infrared excess from a dust disk, numerous broad absorption lines from circumstellar gas, and changing transit ...features, likely from fragments of an actively disintegrating asteroid. Here, we present results from a large photometric and spectroscopic campaign with Hubble Space Telescope, Keck, Very Large Telescope (VLT), Spitzer, and many other smaller telescopes from 2015 to 2018. Somewhat surprisingly the ultraviolet (UV) transit depths are always shallower than those in the optical. We develop a model that can quantitatively explain the observed "bluing" and confirm the previous finding that: (1) the transiting objects, circumstellar gas, and white dwarf are all aligned along our line of sight; (2) the transiting object is blocking a larger fraction of the circumstellar gas than of the white dwarf itself. Because most circumstellar lines are concentrated in the UV, the UV flux appears to be less blocked compared to the optical during a transit, leading to a shallower UV transit. This scenario is further supported by the strong anticorrelation between optical transit depth and circumstellar line strength. We have yet to detect any wavelength-dependent transits caused by the transiting material around WD 1145+017.
Fluidic soft sensors have been widely used in wearable devices for human motion capturing. However, thus far, the biocompatibility of the conductive liquid, the linearity of the sensing signal, and ...the hysteresis between the loading and release processes have limited the sensing quality as well as the applications of these sensors. In this paper, silicone based strain and force sensors composed of a novel biocompatible conductive liquid (potassium iodide and glycerol solution) are introduced. The strain sensors exhibit negligible hysteresis up to 5 Hz, with a gauge factor of 2.2 at 1 Hz. The force sensors feature a novel multifunctional layered structure, with microcylinder‐filled channels to achieve high linearity, low hysteresis (5.3% hysteresis at 1 Hz), and good sensitivity (100% resistance increase at a 5 N load). The sensors' gauge factors are stable at various temperatures and humidity levels. These biocompatible, low hysteresis, and high linearity sensors are promising for safe and reliable diagnostic devices, wearable motion capture, and compliant human–computer interfaces.
A new biocompatible electrolyte solution for wearable devices is introduced. This solution is not only safe to the human body, but also has higher conductivity and lower viscosity compared to previously used biocompatible liquids. Fluidic strain and force sensors developed with this new solution have high sensitivities and low hysteresis, are highly linear, and have bandwidths appropriate for human motion detection.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
ABSTRACT
A large fraction of white dwarfs are accreting or have recently accreted rocky material from their planetary systems, thereby ‘polluting’ their atmospheres with elements heavier than helium. ...In recent years, the quest for mechanisms that can deliver planetesimals to the immediate vicinity of their central white dwarfs has stimulated a flurry of modelling efforts. The observed time evolution of the accretion rates of white dwarfs through their multi-Gyr lifetime is a crucial test for dynamical models of evolved planetary systems. Recent studies of cool white dwarf samples have identified a significant decrease of the mass accretion rates of cool, old white dwarfs over Gyr time-scales. Here, we revisit those results using updated white dwarf models and larger samples of old polluted H- and He-atmosphere white dwarfs. We find no compelling evidence for a strong decrease of their time-averaged mass accretion rates for cooling times between 1 and 8 Gyr. Over this period, the mass accretion rates decrease by no more than a factor of the order of 10, which is one order of magnitude smaller than the decay rate found in recent works. Our results require mechanisms that can efficiently and consistently deliver planetesimals inside the Roche radius of white dwarfs over at least 8 Gyr.
From the perspective of network attackers, finding attack sequences that can cause significant damage to network controllability is an important task, which also helps defenders improve robustness ...during network constructions. Therefore, developing effective attack strategies is a key aspect of research on network controllability and its robustness. In this paper, we propose a Leaf Node Neighbor-based Attack (LNNA) strategy that can effectively disrupt the controllability of undirected networks. The LNNA strategy targets the neighbors of leaf nodes, and when there are no leaf nodes in the network, the strategy attacks the neighbors of nodes with a higher degree to produce the leaf nodes. Results from simulations on synthetic and real-world networks demonstrate the effectiveness of the proposed method. In particular, our findings suggest that removing neighbors of low-degree nodes (i.e., nodes with degree 1 or 2) can significantly reduce the controllability robustness of networks. Thus, protecting such low-degree nodes and their neighbors during network construction can lead to networks with improved controllability robustness.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Large-scale, dense arrays of plasmonic nanodisks on low-modulus, high-elongation elastomeric substrates represent a class of tunable optical systems, with reversible ability to shift key optical ...resonances over a range of nearly 600 nm at near-infrared wavelengths. At the most extreme levels of mechanical deformation (strains >100%), nonlinear buckling processes transform initially planar arrays into three-dimensional configurations, in which the nanodisks rotate out of the plane to form linear arrays with “wavy” geometries. Analytical, finite-element, and finite-difference time-domain models capture not only the physics of these buckling processes, including all of the observed modes, but also the quantitative effects of these deformations on the plasmonic responses. The results have relevance to mechanically tunable optical systems, particularly to soft optical sensors that integrate on or in the human body.
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IJS, KILJ, NUK, PNG, UL, UM
Titanium dioxide nanoparticles (TiO
2
NPs) are widely found in consumer and industrial products, contributing to their prevalent presence in our surroundings. In this study, several miRNAs in the ...immuno-related pathways were found to be dysregulated in RAW264.7 cells after 24-h exposure to TiO
2
NPs, including
miR-29b-3p
, which had not been previously found to be associated with the dysregulation of immunity after exposure to TiO
2
NPs. The KEGG pathway and GO enrichment analysis suggested that
miR-29b-3p
functioned both in the T and B cell receptor signaling pathways. The NFAT5 gene was predicted to regulate
miR-29b-3p
using the MiRDB online database. The expression of
miR-29b-3p
and NFAT5 was found to be inversely correlated using qRT-PCR and western blotting analysis. Dual-luciferase reporter gene assays demonstrated the precise regulatory relationship between
miR-29b-3p
and NFAT5. The upregulation of
miR-29b-3p
was found to reinforce the apoptosis of cells, while no changes were found in terms of the cell cycle or cell proliferation, using MTT, cell apoptosis, and cycle detection experiments. Our results demonstrate that
miR-29b-3p
is involved in the response of RAW264.7 cells to exposure to TiO
2
, proving evidence for the further study of the toxicity and mechanisms of nano-TiO
2
exposure.
Alzheimer’s disease (AD) is the most common neurodegenerative disorder leading to dementia in the elderly, and the mechanisms of AD are not fully defined. MicroRNAs (miRNAs) have been shown to ...contribute to memory deficits in AD. In this study, we identified that miR-204-3p was downregulated in the hippocampus and plasma of 6-month-old APPswe/PS1dE9 (APP/PS1) mice. miR-204-3p overexpression attenuated memory and synaptic deficits in APP/PS1 mice. The amyloid levels and oxidative stress were decreased in the hippocampus of APP/PS1 mice after miR-204-3p overexpression. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (Nox4) was a target of miR-204-3p, and Nox4 inhibition by GLX351322 protected neuronal cells against Aβ1–42-induced neurotoxicity. Furthermore, GLX351322 treatment rescued synaptic and memory deficits, and decreased oxidative stress and amyloid levels in the hippocampus of APP/PS1 mice. These results revealed that miR-204-3p attenuated memory deficits and oxidative stress in APP/PS1 mice by targeting Nox4, and miR-204-3p overexpression and/or Nox4 inhibition might be a potential therapeutic strategy for AD treatment.
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Zhu and colleagues demonstrate that miR-204-3p attenuates memory and synaptic deficits in APPswe/PS1dE9 (APP/PS1) mice via inhibition of NADPH oxidase 4 (Nox4). In addition, Nox4 inhibition by GLX351322 rescues memory deficits in APP/PS1 mice, suggesting that miR-204-3p overexpression and/or Nox4 inhibition is a potential therapeutic strategy for Alzheimer’s disease treatment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
We present observations and analyses of eight white dwarf stars (WDs) that have accreted rocky material from their surrounding planetary systems. The spectra of these helium-atmosphere WDs ...contain detectable optical lines of all four major rock-forming elements (O, Mg, Si, and Fe). This work increases the sample of oxygen-bearing WDs with parent body composition analyses by roughly 33%. To first order, the parent bodies that have been accreted by the eight WDs are similar to those of chondritic meteorites in relative elemental abundances and oxidation states. Seventy-five percent of the WDs in this study have observed oxygen excesses implying volatiles in the parent bodies with abundances similar to those of chondritic meteorites. Three WDs have oxidation states that imply more reduced material than found in CI chondrites, indicating the possible detection of Mercury-like parent bodies, but are less constrained. These results contribute to the recurring conclusion that extrasolar rocky bodies closely resemble those in our solar system, and do not, as a whole, yield unusual or unique compositions.
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