bluuebunny/crossref_metadata_2025_split huggingface dataset:
NGTS-21b: an inflated Super-Jupiter orbiting a metal-poor K dwarf
Authors: Alves Douglas R , Jenkins James S , Vines Jose I , Nielsen Louise D , Gill Samuel , Acton Jack S , Anderson D R , Bayliss Daniel , Bouchy François , Breytenbach Hannes , Bryant Edward M , Burleigh Matthew R , Casewell Sarah L , Eigmüller Philipp , Gillen Edward , Goad Michael R , Günther Maximilian N , Henderson Beth A , Kendall Alicia , Lendl Monika , Moyano Maximiliano , Sefako Ramotholo R , Smith Alexis M S , Costes Jean C , Tilbrook Rosanne H , Thomas Jessymol K , Udry Stéphane , Watson Christopher A , West Richard G , Wheatley Peter J , Worters Hannah L , Osborn Ares 
Published: October 2022

ABSTRACT
We report the discovery of NGTS-21b , a massive hot Jupiter orbiting a low-mass star as part of the Next Generation Transit Survey (NGTS). The planet has a mass and radius of 2.36 ± 0.21 MJ and 1.33 ± 0.03 RJ, and an orbital period of 1.543 d. The host is a K3V (Teff = 4660 ± 41 K) metal-poor ([Fe/H] = −0.26 ± 0.07 dex) dwarf star with a mass and radius of 0.72 ± 0.04 M⊙ and 0.86 ± 0.04R⊙. Its age and rotation period of $10.02^{+3.29}_{-7.30}$ Gyr and 17.88 ± 0.08 d, respectively, are in accordance with the observed moderately low-stellar activity level. When comparing NGTS-21b with currently known transiting hot Jupiters with similar equilibrium temperatures, it is found to have one of the largest measured radii despite its large mass. Inflation-free planetary structure models suggest the planet’s atmosphere is inflated by $\sim \! 21{{\ \rm per\ cent}}$, while inflationary models predict a radius consistent with observations, thus pointing to stellar irradiation as the probable origin of NGTS-21b’s radius inflation. Additionally, NGTS-21b’s bulk density (1.25 ± 0.15 g cm–3) is also amongst the largest within the population of metal-poor giant hosts ([Fe/H] &lt; 0.0), helping to reveal a falling upper boundary in metallicity–planet density parameter space that is in concordance with core accretion formation models. The discovery of rare planetary systems such as NGTS-21 greatly contributes towards better constraints being placed on the formation and evolution mechanisms of massive planets orbiting low-mass stars.
Bark and sapwood water storage and the atypical pattern of recharge and discharge of water reservoirs indicate low vulnerability to drought inAraucaria araucana
Authors: Bucci Sandra Janet , Carbonell-Silletta Luisina , Cavallaro Agustin , Arias Nadia Soledad , Campanello Paula Inés , Goldstein Guillermo , Scholz Fabián Gustavo 
Published: October 2022

AbstractStored water in inner tissues influences the plant water economy, which might be particularly relevant for trees facing increasing dry conditions due to climate change. We studied the water storage in the inner bark and the sapwood of Araucaria araucana (Molina) K. Koch. This species has an extremely thick inner bark and thus it can be used as a model system to assess the impact of internal water storage on plant water balance. Specifically, we analyzed the water circulation pathways in and out of the elastic water storages by using simultaneously frequency domain moisture sensors and dendrometers inserted in the inner bark and in the sapwood, and sap flow determinations during the dry season. The daily patterns of water content and expansion and contraction of the stem tissues were similar to the sap flow pattern. The whole-stem water content and diameter increased in the morning and decreased in the afternoon, contrary to the typical pattern observed in most tree species. An osmotic gradient favoring the water influx from sapwood to inner bark was observed in the morning. There were no lags in the onset of sap flow between different stem heights at the time that recharge of reservoirs occurred. Sap flow at 6 m height was higher than basal sap flow in the afternoon, when the sapwood water content started to decline followed by the water content of the inner bark. Inner bark and sapwood contributed 5–11% to total daily transpiration, allowing the maintenance of high water potentials in the dry season. Our results suggest that the stored water in the stems, the atypical dynamic of recharge and discharge of water from reservoirs and the high tissue capacitance may make an important contribution to the survival of A. araucana during drought periods by maintaining the water balance.
Acoustic waves in saturated porous media with gas bubbles
Authors: Kurzeja Patrick , Steeb Holger 
Published: October 2022

The present framework employs various interface characteristics of gas bubbles into a continuum description of acoustics in porous media. It first extends the bubble compressibility in classic models by surface tension and higher-order curvature effects. This modelling extension is significantly relevant to estimate the impact of interface effects, e.g. on emerging nano-scale bubbles or pickering emulsions. The gas bubble dynamics is then homogenized to derive a manageable set of continuum equations. Respective assumptions and limitations are summarized in this process to provide a quick reference when choosing the compromise between a model’s complexity and applicability. The acoustic response of a water-saturated sandstone with gas bubbles is finally evaluated with respect to the practical importance at ambient and reservoir conditions. The shape of the bubble-size distribution is represented in the evolution of the inverse quality factor but less distinct in the dispersion of the phase velocity. The presented, rigorous framework thus allows to predict what frequencies and acoustic properties relate to specific gas bubble sizes and whether respective signals may be detected with current apparatus.
This article is part of the theme issue ‘Wave generation and transmission in multi-scale complex media and structured metamaterials (part 2)’.
Viscoelastic reduced enhanced isotropic continua as acoustic metamaterials
Authors: Grekova Elena F. 
Published: October 2022

We consider a linear enhanced viscoelastic continuum of general nature but of specific type. Namely, we consider a reduced elastic continuum, satisfying Lagrange equations, where the strain energy depends on a certain (special) vectorial generalized coordinate, but does not depend on its gradient, and then add linear dissipation to the existing elastic connections. We may also represent this model as a ‘bearing continuum’, where all the connections are present (described by one vectorial generalized coordinate), enriched in each point by a ‘distributed dynamic absorber’ (described by ‘special’ vectorial generalized coordinate). We look for free harmonic waves in this infinite medium and obtain a reduced spectral problem for the vectorial generalized coordinate of the bearing continuum, for an arbitrary number of degrees of freedom. It was shown earlier that under certain symmetry conditions in the elastic case we obtain a single negative acoustic metamaterial, i.e. a medium that has band gaps. Further, we consider isotropic and gyrotropic reduced media, described by two three-dimensional vectorial generalized coordinates. First, we generalize results of previous studies for more complex elastic coupling, discovering a polarized shear wave, which has both bandgaps and zones of anomalous refraction. Then we introduce linear dissipation of different kinds. We find that viscosity yields in existence of travelling harmonic waves for all frequencies, possibly except for some points. Logarithmic decrement, infinite for the elastic material in bandgaps, becomes finite and decreases as the dissipation increases, at least for small viscosity. An important observation is: an infinitesimal dissipation in most cases transforms bandgaps into zones of travelling evanescent waves that partially are zones of anomalous refraction (decreasing parts of dispersion curves), where the medium is a double negative acoustic metamaterial.
This article is part of the theme issue ‘Wave generation and transmission in multi-scale complex media and structured metamaterials (part 2)’.
Direction-selective non-reciprocal mechanical energy splitter
Authors: Rakhimzhanova Anar , Brun Michele 
Published: October 2022

A direction-selective elastic micro-structured medium is proposed. The lattice model combines constitutive nonlinearity, a threshold activation displacement and the gyroscopic effect of an isolated spinner to induce a tunable wave deviation on a selected direction in a full non-reciprocal way. The direction-selective effect is quantified in terms of energy flux dependence on gyricity and propagation velocity of the incident wave. Three different regimes are identified, addressed as passing, highly directive and barrier. The nonlinear system sustains solitary waves, described both numerically and through an analytical approximation, which show that the wave is univocally determined by the propagation velocity. A final analysis demonstrates the non-reciprocal mechanism originated by the proposed micro-structured medium.
This article is part of the theme issue ‘Wave generation and transmission in multi-scale complex media and structured metamaterials (part 2)’.
Bioinspired periodic panels optimized for acoustic insulation
Authors: Dal Poggetto Vinícius F. , Pugno Nicola M. , Arruda José Roberto de F. 
Published: October 2022

The design of structures that can yield efficient sound insulation performance is a recurring topic in the acoustic engineering field. Special attention is given to panels, which can be designed using several approaches to achieve considerable sound attenuation. Previously, we have presented the concept of thickness-varying periodic plates with optimized profiles to inhibit flexural wave energy propagation. In this work, motivated by biological structures that present multiple locally resonant elements able to cause acoustic cloaking, we extend our shape optimization approach to design panels that achieve improved acoustic insulation performance using either thickness-varying profiles or locally resonant attachments. The optimization is performed using numerical models that combine the Kirchhoff plate theory and the plane wave expansion method. Our results indicate that panels based on locally resonant mechanisms have the advantage of being robust against variation in the incidence angle of acoustic excitation and, therefore, are preferred for single-leaf applications.
This article is part of the theme issue ‘Wave generation and transmission in multi-scale complex media and structured metamaterials (part 2)’.
Dynamic fracture regimes for initially prestressed elastic chains
Authors: Nieves Michael J. , Livasov Pavlos , Mishuris Gennady 
Published: October 2022

We study the propagation of a bridge crack in an anisotropic multi-scale system involving two discrete elastic chains that are interconnected by links and possess periodically distributed inertia. The bridge crack is represented by the destruction of every other link between the two elastic chains, and this occurs with a uniform speed. This process is assumed to be sustained by energy provided to the system through its initial configuration, corresponding to the alternating application of compression and tension to neighbouring links. The solution, based on the Wiener–Hopf technique and presented in Ayzenberg-Stepanenko
et a
l
. (Ayzenberg-Stepanenko
et al.
2014
Proc. R. Soc. A
470
, 20140121 (
doi:10.1098/rspa.2014.0121
)) is used to compute the profile of the medium undergoing failure. We investigate when this solution, representing the steady failure process, is physically acceptable. It is shown that the analytical solution is not always physically applicable and can be used to determine the onset of non-steady failure regimes. These arise from the presence of critical deformations in the wake of the crack front at the sites of the intact links. Additionally, we demonstrate that the structural integrity of the discrete elastic chains can significantly alter the range of speeds for which the bridge crack can propagate steadily.

This article is part of the theme issue ‘Wave generation and transmission in multi-scale complex media and structured metamaterials (part 2)’.
On the adoption of canonical quasi-crystalline laminates to achieve pure negative refraction of elastic waves
Authors: Chen Zhijiang , Morini Lorenzo , Gei Massimiliano 
Published: October 2022

A way to achieve negative refraction of elastic anti-plane shear waves is a transmission across an interface between a homogeneous substrate and a periodic transverse laminate. To achieve
pure
negative refraction, the frequency of the source should be lower than the upper limit of the second transition zone (TZ) of the harmonic spectrum of the laminate. An effective way to control the location of TZ is to consider a
canonical
configuration for the laminate, a concept that originates from the properties of quasi-crystalline sequences among which the Fibonacci one is a particular case. Based on the universal structure of frequency spectrum, we provide a method based on the reduced torus to study the effect of a change in canonical ratio on the limits of the TZ. A further contribution consists in the analytical estimate of the angle of refraction for a linear relationship between frequency and longitudinal wavenumber. This is achieved by determining the components of the in-plane Poynting vector. The outcome provides a tool for the selection of a suitable laminate-substrate combination to accomplish a particular angle of the refracted wave. Finally, it is shown that for some particular configurations, the transmitted energy displays a peak that can be exploited to maximize the amount of energy travelling across the laminate.

This article is part of the theme issue ‘Wave generation and transmission in multi-scale complex media and structured metamaterials (part 2)’.
Models for resonant acoustic metasurfaces with application to moth wing ultrasound absorption
Authors: Wang Yao-Ting , Shen Zhiyuan , Neil Thomas R. , Holderied Marc W. , Skelton Elizabeth A. , Craster Richard V. 
Published: October 2022

Taking as bioinspiration the remarkable acoustic absorption properties of moth wings, we develop a simple analytical model that describes the interaction between acoustic pressure fields, and thin elastic plates incorporating resonant sub-structures. The moth wing is an exemplar of a natural acoustic metamaterial; the wings are deeply subwavelength in thickness at the frequencies of interest, the absorption is broadband and the tiny scales resonate on the moth wing acting in concert. The simplified model incorporates only the essential physics and the scales are idealized to flat rigid rectangular plates coupled via a spring to an elastic plate that forms the wing; all the components are deep-subwavelength at desired frequencies. Based on Fourier analysis, complemented by phenomenological modelling, our theory shows excellent agreement with simulation mimicking the moth-wing structure. Moth wings operate as broadband sound absorbers employing a range of scale sizes. We demonstrate that a random distribution of scale sizes generates a broadband absorption spectrum. To further illustrate the potential of the model, we design a deeply sub-wavelength acoustic counterpart of electromagnetically induced reflectance.
This article is part of the theme issue ‘Wave generation and transmission in multi-scale complex media and structured metamaterials (part 2)’.
Active exterior cloaking of an inclusion with evanescent multipole devices for flexural waves in thin plates
Authors: Allison F. J. P. , Selsil Ö. , Haslinger S. G. 
Published: October 2022

We present an active exterior cloak for flexural waves propagating in a Kirchhoff plate of infinite extent. The evanescent multipole devices are characterized by Macdonald functions

K
n

of the required order, which, assuming time-harmonic vibrations, are solutions of the fourth-order biharmonic equation. It is shown that in the region of interfering waves, which emanate from the devices, a field is recreated which cancels the incident wave to yield a region of ‘stillness’. An inclusion is then positioned in this region for further investigation, with additional attention given to the boundary condition.

This article is part of the theme issue ‘Wave generation and transmission in multi-scale complex media and structured metamaterials (part 2)’.
Active exterior cloaking for the two-dimensional Helmholtz equation with complex wavenumbers and application to thermal cloaking
Authors: Cassier Maxence , DeGiovanni Trent , Guenneau Sébastien , Guevara Vasquez Fernando 
Published: October 2022

We design sources for the two-dimensional Helmholtz equation that can cloak an object by cancelling out the incident field in a region, without the sources completely surrounding the object to hide. As in previous work for real positive wavenumbers, the sources are also determined by the Green identities. The novelty is that we prove that the same approach works for complex wavenumbers which makes it applicable to a variety of media, including media with dispersion, loss and gain. Furthermore, by deriving bounds on Graf’s addition formulas with complex arguments, we obtain new estimates that allow to quantify the quality of the cloaking effect. We illustrate our results by applying them to achieve active exterior cloaking for the heat equation.This article is part of the theme issue ‘Wave generation and transmission in multi-scale complex media and structured metamaterials (part 2)’.
The Herschel-Quincke tube with modulated branches
Authors: Papathanasiou T. K. , Tsolakis E. , Spitas V. , Movchan A. B. 
Published: October 2022

The Herschel-Quincke (HQ) tube concept for transmission loss in pipe systems is expanded to include cases of branches with modulated properties. Modulated waveguides, featuring corrugations in their geometry or speed of sound, are known to produce significant reflection even without the parallel branch of the HQ tube. The HQ tube, in its classical form, produces narrow banded transmission loss at frequencies related to the length, wavenumber and cross-section area of the parallel branch. The modulated Herschel-Quincke (MHQ) tube combines these attributes to produce enhanced transmission loss characteristics in terms of both width and number of transmission loss bands. Several modulated profiles for the speed of sound in different branches of the tube are considered and analytical expressions for the transmission loss and resonant conditions are derived. Detailed analysis of periodically stratified branch profiles demonstrates the effectiveness of the MHQ tube for fluid-borne noise attenuation in pipe systems.
This article is part of the theme issue 'Wave generation and transmission in multi-scale complex media and structured metamaterials (part 2)'.
An advanced sequence clustering and designation workflow reveals the enzootic maintenance of a dominant West Nile virus subclade in Germany
Authors: Santos Pauline Dianne , Günther Anne , Keller Markus , Homeier-Bachmann Timo , Groschup Martin H. , Beer Martin , Höper Dirk , Ziegler Ute 
Published: October 2022

AbstractWest Nile virus (WNV) is the most widespread arthropod-borne (arbo) virus and the primary cause of arboviral encephalitis globally. Members of WNV species genetically diverged and are classified into different hierarchical groups below species rank. However, the demarcation criteria for allocating WNV sequences into these groups remain individual, inconsistent, and the use of names for different levels of the hierarchical levels is unstructured. In order to have an objective and comprehensible grouping of WNV sequences, we developed an advanced grouping workflow using the “affinity propagation clustering”-algorithm and newly included the “agglomerative hierarchical clustering”-algorithm for the allocation of WNV sequences into different groups below species rank. In addition, we propose to use a fixed set of terms for the hierarchical naming of WNV below species level and a clear decimal numbering system to label the determined groups. For validation, we applied the refined workflow to WNV sequences that have been previously grouped into various lineages, clades, and clusters in other studies. Although our workflow regrouped some WNV sequences, overall, it generally corresponds with previous groupings. We employed our novel approach to the sequences from the WNV circulation in Germany 2020, primarily from WNV-infected birds and horses. Besides two newly defined minor (sub)clusters comprising only of three sequences each, subcluster 2.5.3.4.3c was the predominant WNV sequence group detected in Germany from 2018-20. This predominant subcluster was also associated with at least five human WNV-infections in 2019-20. In summary, our analyses imply that the genetic diversity of the WNV population in Germany is shaped by enzootic maintenance of the dominant WNV subcluster accompanied by sporadic incursions of other rare clusters and subclusters. Moreover, we show that our refined approach for sequence grouping yields meaningful results. Although we primarily aimed at a more detailed WNV classification, the presented workflow can also be applied to the objective genotyping of other virus species.
Super-resolution ultrasound imaging of cerebrovascular impairment in a mouse model of Alzheimer’s disease
Authors: Lowerison Matthew R. , Chandra Sekaran Nathiya Vaithiyalingam , Dong Zhijie , Chen Xi , You Qi , Llano Daniel A. , Song Pengfei 
Published: October 2022

AbstractIncreasing evidence has suggested a link between cerebrovascular disease and the cognitive impairment of patients with Alzheimer’s disease. However, cerebrovascular disease and Alzheimer’s disease share several risk factors making it unclear whether cerebrovascular deficiency and Alzheimer’s disease pathology have additive effects on cognition or if cerebrovascular impairment merely exacerbates existing Alzheimer’s disease-associated cognitive decline. Additionally, early-stage Alzheimer’s disease typically involves hippocampal atrophy, complicating most efforts to elucidate the interplay between cerebral microvascular function and Alzheimer’s disease progression due to the necessity of probing deep-brain structures. The purpose of this study was to demonstrate the use of ultrasound localization microscopy on the 5xFAD mouse model of Alzheimer’s disease (3-month and 6-month-old cohorts) in comparison to age-matched wild-type controls, revealing microvascular scale reconstructions throughout the whole brain depth, to visualize and quantify Alzheimer’s disease-associated vascular impairments. We found that functional decreases in hippocampal and entorhinal flow velocity preceded structural derangements in regional vascular density. In addition to providing global vascular quantifications of deep brain structures with a high local resolution, this technology also permitted hierarchical analysis of individual vessels and, in some cases, potentially allowed for decoupling of arteriole and venous flow contributions. Co-registered histological sectioning confirmed the regionalized hypo-perfusion deficits seen on ultrasound imaging, which were co-localized with amyloid beta plaque deposition.Significance statementThe study of the impact of cerebrovascular disease on Alzheimer’s disease pathology is complicated by the need to image deep-brain structures with high vascular fidelity. We demonstrate that ultrasound localization microscopy, a super-resolution acoustic imaging technique, is capable of imaging cerebrovasculature throughout the entire depth of the brain at a microvascular scale. This technology was applied to the 5xFAD mouse model of Alzheimer’s disease, where it was found that 5xFAD animals have significant impairments in vascular function in the entorhinal cortex and hippocampal region in comparison to age matched controls at the 3-month timepoint. Structural derangements in cerebrovasculature were only observed in the 6-month-old animal cohorts, with a maintained impairment in vascular function.