General Field Research Articles

Carroll covariant scalar fields in two dimensions

Conformal Carroll symmetry generically arises on null manifolds and is important for holography of asymptotically flat spacetimes, generic black hole horizons and tensionless strings. In this paper, we focus on two dimensional (2d) null manifolds and hence on the 2d Conformal Carroll or equivalently the 3d Bondi-Metzner-Sachs (BMS) algebra. Using Carroll covariance, we write the most general free massless Carroll scalar field theory and discover three inequivalent actions. Of these, two viz. the time-like and space-like actions, have made their appearance in literature before. We uncover a third that we call the mixed-derivative theory. As expected, all three theories enjoy off-shell BMS invariance. Interestingly, we find that the on-shell symmetry of mixed derivative theory is a single Virasoro algebra instead of the full BMS. We discuss potential applications to tensionless strings and flat holography.

Interaction of Chondroitin and Hyaluronan Glycosaminoglycans with Surfaces of Carboxylated Carbon Nanotubes Studied Using Molecular Dynamics Simulations

Interaction of β-D-glucopyranuronic acid (GlcA), N-acetyl-β-D-glucosamine (GlcNAc), N-acetyl-β-D-galactosamine (GalNAc) and two natural decameric glycosaminoglycans, hyaluronic acid (HA) and Chondroitin (Ch) with carboxylated carbon nanotubes, were studied using molecular dynamics simulations in a condensed phase. The force field used for carbohydrates was the GLYCAM-06j version, while functionalized carbon nanotubes (fCNT) were described using version two of the general amber force field. We found a series of significant differences in carbohydrate-fCNT adsorption strength depending on the monosaccharide molecule and protonation state of surface carboxyl groups. GlcNAc and GalNAc reveal a strong adsorption on fCNT with deprotonated carboxyl groups, and a slightly weaker adsorption on the fCNT with protonated carboxyl groups. On the contrary, GlcA weakly adsorbs on fCNT. The change in protonation state of surface carboxyl groups leads to the reversal orientation of GlcNAc and GalNAc in reference to the fCNT surface, while GlcA is not sensitive to that factor. Adsorption of decameric oligomers on the surface of fCNT weakens with the increasing number of monosaccharide units. Chondroitin adsorbs weaker than hyaluronic acid and incorporation of four Ch molecules leads to partial detachment of them from the fCNT surface. The glycan-fCNT interactions are strong enough to alter the conformation of carbohydrate backbone; the corresponding conformational changes act toward a more intensive contact of glycan with the fCNT surface. Structural and energetic features of the adsorption process suggest the CH-π interaction-driven mechanism.

Fifth forces and frame invariance

I discuss how one can apply the covariant formalism developed by Vilkovisky and DeWitt to obtain frame invariant fifth force calculations for scalar-tensor theories. Fifth forces are severely constrained by astrophysical measurements. It was shown previously that for scale-invariant Higgs-dilaton gravity, in a particular choice of frame, the dilaton fifth force is dramatically suppressed, evading the observational constraints. Using a geometric approach I extend this result to all frames, and show that the usual dichotomy of ``Jordan frame'' versus ``Einstein frame'' is better understood as a continuum of frames: submanifold slices of a more general field space.

Approximate streamsurfaces for flow visualization

Instantaneous features of three-dimensional velocity fields are most directly visualized via streamsurfaces. It is generally unclear, however, which streamsurfaces one should pick for this purpose, given that infinitely many such surfaces pass through each point of the flow domain. Exceptions to this rule are vector fields with a non-degenerate first integral whose level surfaces globally define a continuous, one-parameter family of streamsurfaces. While generic vector fields have no first integrals, their vortical regions may admit local first integrals over a discrete set of streamtubes, as Hamiltonian systems are known to do over Cantor sets of invariant tori. Here we introduce a method to construct such first integrals approximately from velocity data, and show that their level sets indeed frame vortical features of the velocity field in examples in which those features are known from Lagrangian analysis. Moreover, we test our method in numerical datasets, including a flow inside a V-junction and a turbulent channel flow. For the latter, we propound an algorithm to pin down the most salient barriers to momentum transport up to a given scale providing a way out of the occlusion conundrum that typically accompanies other vortex visualization methods.

Amplitude/operator basis in chiral perturbation theory

We establish a systematic construction of the on-shell amplitude/operator basis for Chiral Perturbation Theory (ChPT) in D = 4 spacetime dimensions and with an arbitrary number of flavors Nf. For kinematic factors, we employ spinor-helicity variables to construct the soft blocks, which are local amplitudes satisfying the Adler’s zero condition, as well as to take into account the reduction in the kinematic basis due to the Gram determinant, which arises at O(p10) when the number of multiplicity N in an amplitude becomes large: N > D. For flavor factors, we include group-theoretic relations at small Nf, Nf≤ N, which decreases the flavor basis. The result is obtained by adapting the Young tensor method of constructing the operator basis for generic effective field theories to the case of non-linearly realized symmetries. Working in the massless quark limit, we present purely mesonic operators for both even- and odd-parity at O(p6) and O(p8) for N = 6 and arbitrary Nf, and establish a direct correspondence between the amplitude basis and the operator basis. Furthermore, the redundancy due to the Gram determinant is studied at O(p10) for N = 6, 8 and 10.

Vane–Probe Interactions in Transonic Flows

AbstractIn this article, a numerical investigation of the effect of a miniaturized five-hole probe downstream of a transonic low-pressure turbine vane row is presented. First, a numerical calibration of the probe was performed in uniform flow conditions, as is the case for any traditional calibration, for a wide range of Mach number, yaw angle, and pitch angle conditions. The effect of the probe on the general flow field throughout the turbine vane segments was then evaluated by performing a comparison between a setup with vanes only (no probe) and with vanes and probes. It was found that, as the probe traverses downstream the vane, the probe impact on the vane isentropic Mach number depends on the probe circumferential position. The highest impact was observed when the probe is located at the upper mid-passage (θ = 0.5), consisting of a relatively small reduction of the isentropic Mach number on the vane suction side of just 0.02. To assess the accuracy of the quantities “measured” by the probe, the probe-determined flow field was compared to the flow field of the vanes-only setup. A nonnegligible modification of the probe-determined local distributions of Mach number, yaw angle, and pitch angle is revealed with respect to the undisturbed flow. Further investigation involving stagnation point tracking showed that the artificial high circumferential variation of the yaw angle is not caused by a modification of the vane outlet flow angle, but is induced by nonuniform flow conditions downstream of the vanes. With knowledge of the above, a two-step correction is used to account for the effects of the nonuniformity of the flow, and its impact is evaluated on 2D and 3D flow regions. A significative effect of the correction was found on the probe-determined yaw angle, in which the difference from the vanes-only data was reduced to below 1 deg, except near the endwalls where larger discrepancies remain due to probe–endwall interactions. A shortfall of the correction was instead observed on the probe-determined Mach numbers. Finally, the pitch-wise averaged quantities were evaluated. It was observed that the highest differences between probe-determined and undisturbed data occur where radial gradients of total pressure are stronger and that the two-step correction had almost negligible impact on the pitch-wise averaged quantities.

Editorial: Nanocomposites with interfaces controlled by grafted or adsorbed polymers

adsorbing polymer molecules can modify both the interfacial physics and the filler structure, giving access 14 to improved macroscopic (mechanical, electrical, or optical) material properties.It is the aim of the present topical collection to focus on some aspects of recent research in this 16 highly active and evolving area. We review and summarize state-of-the-art investigations of polymer 17 nanocomposite materials which promote at a better understanding and control of the complex behavior of 18 nanocomposites. Two articles with original experimental approaches have been contributed, one presenting 19 an innovative application of microgel-nanoparticle composites in solvent, the other an in-depth study of the 20 structure and dynamics of a bulk polymer nanocomposite. In parallel, we have reviewed the general field 21 of particle and polymer structure and dynamics using scattering techniques, in particular neutron scattering, 22 and highlighted the role of interfacial polymer layers in the specific case of polymer-grafted nanoparticles 23 in a second review.Nanocomposites can have many faces and may serve for fundamental studies as well as applications.

Molecular Dynamics-Assisted Interaction of Vanadium Complex-AMPK: From Force Field Development to Biological Application for Alzheimer's Treatment.

A large part of the world's population is affected by Alzheimer's disease (AD) and diabetes mellitus type 2, which cause both social and economic impacts. These two conditions are associated with one protein, AMPK. Studies have shown that vanadium complexes, such as bis(N',N'-dimethylbiguanidato)-oxovanadium(IV), VO(metf)2·H2O, are potential agents against AD. A crucial step in drug design studies is obtaining information about the structure and interaction of these complexes with the biological targets involved in the process through molecular dynamics (MD) simulations. However, MD simulations depend on the choice of a good force field that could present reliable results. Moreover, general force fields are not efficient for describing the properties of metal complexes, and a VO(metf)2·H2O-specific force field does not yet exist; thus, the proper development of a parameter set is necessary. Furthermore, this investigation is essential and relevant given the importance for both the scientific community and the population that is affected by this neurodegenerative disease. Therefore, the present work aims to develop and validate the AMBER force field parameters for VO(metf)2·H2O since the literature lacks such information on metal complexes and investigate through classical molecular dynamics the interactions made by the complex with the protein. The proposed force field proved to be effective for describing the vanadium complex (VC), supported by different analyses and validations. Moreover, it had a great performance when compared to the general AMBER force field. Beyond that, MD findings provided an in-depth perspective of vanadium complex-protein interactions that should be taken into consideration in future studies.

Exploring the stellar populations of backsplash galaxies

Abstract Backsplash galaxies are those that traverse and overshoot cluster cores as they fall into these structures. They are affected by environment, and should stand out in contrast to the infalling population. We target galaxies in the vicinity of clusters (R≳R200) and select a sample in projected phase space (PPS), from the compilation of Sampaio et al. based on SDSS data. We present a statistical analysis, comparing two regions in PPS, with the same projected distance to the cluster but different velocity. The analysis relies on the presence of variations in the stellar population content of backsplash galaxies. We find a lower limit in the fractional contribution of ∼5 per cent with respect to the general sample of infalling galaxies at similar group-centric distance when using single line strength analysis, or ∼15-30 per cent when adopting bivariate distributions. The stellar populations show a subtle but significant difference towards older ages, and a higher fraction of quiescent galaxies. We also compare this set with a general field sample, where a substantially larger difference in galaxy properties is found, with the field sample being consistently younger, metal poorer and with a lower fraction of quiescent galaxies. Noting that our ‘cluster’ sample is located outside of the virial radius, we expect this difference to be caused by pre-processing of the infalling galaxies in the overall higher density regions.

The trilobite Pseudoblackwelderia lubrica (Damesellidae) from the Cambrian (Guzhangian) Changhia Formation of Northern Anhui, China, and its potential sexual dimorphism

The North China type Cambrian System is well developed in northern Anhui Province. A large number of specimens of the trilobite Pseudoblackwelderia lubrica were collected from the Guzhangian (later Cambrian) Changhia Formation at Fenghuangshan in northern Anhui, China, prompting a redefinition of the species. Our emended diagnosis includes: a cone-shaped glabella that is broadly to acutely rounded anteriorly; three pairs of glabellar furrows; the preglabellar field being absent or very short; the librigena with a narrow lateral border, a broad general field and long genal spine; the pygidium with four rings and a terminal piece on the axis; six or seven pairs of pygidial spines with the anterior five pairs being short, the posterolateral pair being long and stout, the seventh pair being small or absent. The new specimens suggest that Neimengguasps is a junior synonym of Pseudoblackwelderia. Moreover, the presence or absence of paired spines on the posterior margin of pygidium is attributed to potential sexual dimorphism. Qianping Lei [cicelyapple@126.com], Nature Department, Changzhou Museum, Changzhou, Jiangsu Province, 213022, PR China Qing Liu [qingliu1029@yeah.net], Room 104, Unit A, Building Six, Fenghuanghu No. 1, Xinbei District, Changzhou 213125, PR China Shanchi Peng [scpeng@nigpas.ac.cn], State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing 210008, China; Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, PR China.

Temporal-Domain Adaptation for Satellite Image Time-Series Land-Cover Mapping With Adversarial Learning and Spatially Aware Self-Training

Nowadays, Satellite Image Time Series (SITS) are commonly employed to derive land cover maps (LCM) to support decision makers in a variety of land management applications. In the most general workflow, the production of LCM strongly relies on available ground truth data to train supervised machine learning models. Unfortunately, this data is not always available due to time-consuming and costly field campaigns. In this scenario, the possibility to transfer a model learnt on a particular year ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">source domain</i> ) to a successive period of time ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">target domain</i> ), over the same study area, can save time and money. Such a kind of model transfer is challenging due to different acquisition conditions affecting each time period thus, resulting in possible distribution shifts between <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">source</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">target</i> domains. In the general field of machine learning, Unsupervised Domain Adaptation (UDA) approaches are well suited to cope with the learning of models under distribution shifts between <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">source</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">target</i> domains. While widely explored in the general computer vision field, they are still under investigated for SITS-based land cover mapping, especially for the temporal transfer scenario. With the aim to cope with this scenario in the context of SITS-based land cover mapping, here we propose Spatially Aligned Domain-Adversarial Neural Network, a framework that combines both adversarial learning and self-training to transfer a classification model from a time period (year) to a successive one on a specific study area. Experimental assessment on a study area located in Burkina Faso characterized by challenging operational constraints demonstrates the significance of our proposal. The obtained results have shown that our proposal outperforms all the UDA competing methods by 7 to 12 points of F1-score across three different transfer tasks.

General Extremal Field Method for Time-Optimal Trajectory Planning in Flow Fields

We present an algorithm to compute time-optimal trajectories for light vehicles in unsteady flow fields, with applications to long-range, low-power aircraft as well as underwater vehicles in ocean currents. The proposed approach aims at unifying various works from the literature on extremal fields and extends it by several features. First, we propose an exact scheme to deal with still obstacles. While being directly useful for pure obstacles, it is also of particular interest to ensure the validity of computation at the borders of the problem domain. Second, we demonstrate the method ability to deal with trajectory planning for long-range airborne missions with real weather data. Lastly, the source code, written in Python, is made open to the community to accelerate research in the domain.

The influence of force fields on the structure and dynamics of water confined in ZIF-8 from atomistic simulations.

The complexity of modeling flexible crystals, such as ZIF-8, mainly stems from the handling of intramolecular interactions. Numerous force fields have been proposed in the literature to describe the interactions between atoms in ZIF-8. We employ seven force fields to examine the structure and dynamic behavior of water molecules confined in ZIF-8, with the aim of investigating the impact of force fields on simulation results. Various structural characterization methods consistently indicate that the choice of different force fields has quantitative effects but no qualitative effects on the structural characteristics of confined water. Additionally, the force fields do not impact the qualitative description of the diffusion mechanism. Both mean-square displacement and van Hove autocorrelation function reveal two characteristic movements of water molecules diffusing in ZIF-8: a short-time intra-cavity hopping process and a long-time inter-cavity hopping process. However, the framework flexibility is found to play a crucial role in determining the order of spatial arrangement and local structure, self-diffusion coefficient and reorientational dynamics of confined water. Specifically, the DREIDING force field gives rise to an unrealistic stiff framework, enhancing the order of spatial arrangement and diminishing the local ordered structure of confined water. Meanwhile, it results in much slower translational and reorientational dynamics. Hence, the general DREIDING force field cannot be considered for providing a quantitative description of the water structure and dynamics.

METALINGUISTIC ASPECTS OF POLITE COMMUNICATION BETWEEN AUTHOR AND READER (based on 18th-century German art history texts)

The article aims to study the metalinguistic characteristics of polite communication. The analysis is carried out on the material of German art history texts of the 18th century. Through the comparison of art history texts written by J. J. Winckelmann, J. G. Herder and H. E. Lessing it is being revealed how and for what purpose the authors of these texts use formulas of politeness. The analysis is based on the theoretical foundations of pragmatic linguistics, sociolinguistics and metatext research. The results show that the actualisers of positive politeness include, for example, adjectives with the meaning of confidence, emotional expressions and the inclusive pronoun wir. By using these tools the author seeks to solidarise with the reader in the general academic field. Negative politeness strategies are used by the author to avoid imposing their views on the reader. The following negative politeness strategies were discovered: showing caution by hedging, demonstrating a lack of desire to impose one’s point of view and attributing all responsibility for what is written by personalisation. The results demonstrate that in research articles the reader is actively, albeit invisibly, present in the text. In general, positive politeness strategies are used by researchers to demonstrate solidarity with the fellow researchers and the research community at large. Negative strategies either depersonalise the information conveyed or, on the contrary, personalise it. Both approaches aim not to put any pressure on the reader.

Formation of a Plasma Layer During the Passage of the Moon through the Magnetic Ropes of the Solar Wind

In the absence of a dense atmosphere and a general magnetic field around the Moon, solar wind particles reach the lunar surface and are almost completely absorbed. When the Moon passes through the plasma medium of the solar wind magnetic ropes, the electric currents of the rope can strongly change the electric potential of the lunar surface on the day and night surfaces, and in the case when the current density vectors of the rope and the direction to the Sun are close to colinear, there is the possibility of sufficiently strong ring currents, the magnetic field of which tends to displace the magnetic field of the rope and lead to the formation of a plasma layer with a height of the order of the electron Larmor radius.

On Euler systems for the multiplicative group over general number fields

On Euler systems for the multiplicative group over general number fields

On the weighted Bojanov-Chebyshev problem and the sum of translates method of Fenton

Minimax and maximin problems are investigated for a special class of functions on the interval $[0,1]$. These functions are sums of translates of positive multiples of one kernel function and a very general external field function. Due to our very general setting the minimax, equioscillation and characterization results obtained extend those of Bojanov, Fenton, Hardin, Kendall, Saff, Ambrus, Ball and Erdélyi. Moreover, we discover a surprising intertwining phenomenon of interval maxima, which provides new information even in the most classical extremal problem of Chebyshev. Bibliography: 25 titles.

ONTOLOGY, DECISION-MAKING, AND VALUES, OR SEVERAL «PHILOSOPHICAL» REMINISCENCES

The paper continues a series of the author’s publications on relationships between philosophy and Welt-anschauung. Its subject is the mechanisms of interaction between ontological attitudes and values in deci-sion-making. It is assumed that philosophy has always, one way or another, strived for their comprehen-sion, and it was the increasing cultural significance of these efforts that contributed to the separation of ontology from the general metaphysical field. The article begins with an analysis of the concept of exist-ence and an explication of the evolutionary premises of situations where the need for decision-making arises. The author refers to the concept of a self-organizing system, the role of informationblocks and the place of selection and choice in its reproduction. Selection is based on predetermined criteria, while choice, with its greater or lesser certainty of the options, on the contrary, implies variability of the agent’s aspirations. In the mainpart of the article, the author introduces the idea of a decision scheme as a model that combines the dynamic and spatial aspects of this phenomenon; relations between being, possibility, and goals are explored. Special attention is given to the importance of spiritual values for the formation of goals and to the cognitive similarity between ontology and the picture of the world as a component of the worldview. Since values exist, the restructuring of metaphysics demanded clarification of the functions of values in decisions. The last section, based on the controversy of Locke and Leibniz over justice, shows that the law of sufficient reason was an epistemic prerequisite for the formation of axiology as a special area of philosophizing. All the material considered makes it possible to present the relationship between the picture of the world and values as the basis of the goal-setting.

Periodic solutions to a nonlinear Dirac-Klein-Gordon system with concave and convex nonlinearities

Using the variational method, we study the existence and multiplicity of periodic solutions to nonlinear Dirac-Klein-Gordon systems with two types of nonlinearities. Both the Dirac field and the Klein–Gordon field considered here are general nonlinear fields, different from previously considered models. Moreover, results for the regularity of the solutions are given. In addition, we obtain the soliton-like solution of Dirac-Klein-Gordon systems by approximation of periodic solutions.

Multifractal analysis of Gaussian multiplicative chaos and applications

Let $M_{\gamma}$ be a subcritical Gaussian multiplicative chaos measure associated with a general log-correlated Gaussian field defined on a bounded domain $D \subset \mathbb{R}^d$, $d \geq 1$. We find an explicit formula for its singularity spectrum by showing that $M_{\gamma}$ satisfies almost surely the multifractal formalism, i.e., we prove that its singularity spectrum is almost surely equal to the Legendre-Fenchel transform of its $L^q$-spectrum. Then, applying this result, we compute the lower singularity spectrum of the multifractal random walk and of the Liouville Brownian motion.