### Recent Submissions

• #### Chiral Helimagnetism and One-Dimensional Magnetic Solitons in a Cr-Intercalated Transition Metal Dichalcogenide

(Advanced Materials, Wiley, 2021-07-24) [Article]
Chiral magnets endowed with topological spin textures are expected to have promising applications in next-generation magnetic memories. In contrast to the well-studied 2D or 3D magnetic skyrmions, the authors report the discovery of 1D nontrivial magnetic solitons in a transition metal dichalcogenide 2H-TaS2 via precise intercalation of Cr elements. In the synthetic Cr1/3TaS2 (CTS) single crystal, the coupling of the strong spin–orbit interaction from TaS2 and the chiral arrangement of the magnetic Cr ions evoke a robust Dzyaloshinskii–Moriya interaction. A magnetic helix having a short spatial period of ≈25 nm is observed in CTS via Lorentz transmission electron microscopy. In a magnetic field perpendicular to the helical axis, the helical spin structure transforms into a chiral soliton lattice (CSL) with the spin structure evolution being consistent with the chiral sine-Gordon theory, which opens promising perspectives for the application of CSL to fast-speed nonvolatile magnetic memories. This work introduces a new paradigm to soliton physics and provides an effective strategy for seeking novel 2D magnets.
• #### Landslide size matters: A new data-driven, spatial prototype

(Engineering Geology, Elsevier BV, 2021-07-24) [Article]
The standard definition of landslide hazard requires the estimation of where, when (or how frequently) and how large a given landslide event may be. The geoscientific community involved in statistical models has addressed the component pertaining to how large a landslide event may be by introducing the concept of landslide-event magnitude scale. This scale, which depends on the planimetric area of the given population of landslides, in analogy to the earthquake magnitude, has been expressed with a single value per landslide event. As a result, the geographic or spatially-distributed estimation of how large a population of landslide may be when considered at the slope scale, has been disregarded in statistically-based landslide hazard studies. Conversely, the estimation of the landslide extent has been commonly part of physically-based applications, though their implementation is often limited to very small regions. In this work, we initially present a review of methods developed for landslide hazard assessment since its first conception decades ago. Subsequently, we introduce for the first time a statistically-based model able to estimate the planimetric area of landslides aggregated per slope units. More specifically, we implemented a Bayesian version of a Generalized Additive Model where the maximum landslide size per slope unit and the sum of all landslide sizes per slope unit are predicted via a Log-Gaussian model. These “max” and “sum” models capture the spatial distribution of (aggregated) landslide sizes. We tested these models on a global dataset expressing the distribution of co-seismic landslides due to 24 earthquakes across the globe. The two models we present are both evaluated on a suite of performance diagnostics that suggest our models suitably predict the aggregated landslide extent per slope unit. In addition to a complex procedure involving variable selection and a spatial uncertainty estimation, we built our model over slopes where landslides triggered in response to seismic shaking, and simulated the expected failing surface over slopes where the landslides did not occur in the past. What we achieved is the first statistically-based model in the literature able to provide information about the extent of the failed surface across a given landscape. This information is vital in landslide hazard studies and should be combined with the estimation of landslide occurrence locations. This could ensure that governmental and territorial agencies have a complete probabilistic overview of how a population of landslides could behave in response to a specific trigger. The predictive models we present are currently valid only for the 25 cases we tested. Statistically estimating landslide extents is still at its infancy stage. Many more applications should be successfully validated before considering such models in an operational way. For instance, the validity of our models should still be verified at the regional or catchment scale, as much as it needs to be tested for different landslide types and triggers. However, we envision that this new spatial predictive paradigm could be a breakthrough in the literature and, in time, could even become part of official landslide risk assessment protocols.
• #### Natural processes dominate the pollution levels during COVID-19 lockdown over India.

(Scientific reports, Springer Science and Business Media LLC, 2021-07-24) [Article]
The lockdown measures that were taken to combat the COVID-19 pandemic minimized anthropogenic activities and created natural laboratory conditions for studying air quality. Both observations and WRF-Chem simulations show a 20-50% reduction (compared to pre-lockdown and same period of previous year) in the concentrations of most aerosols and trace gases over Northwest India, the Indo Gangetic Plain (IGP), and the Northeast Indian regions. It is shown that this was mainly due to a 70-80% increase in the height of the boundary layer and the low emissions during lockdown. However, a 60-70% increase in the pollutants levels was observed over Central and South India including the Arabian sea and Bay of Bengal during this period, which is attributed to natural processes. Elevated (dust) aerosol layers are transported from the Middle East and Africa via long-range transport, and a decrease in the wind speed (20-40%) caused these aerosols to stagnate, enhancing the aerosol levels over Central and Southern India. A 40-60% increase in relative humidity further amplified aerosol concentrations. The results of this study suggest that besides emissions, natural processes including background meteorology and dynamics, play a crucial role in the pollution concentrations over the Indian sub-continent.
• #### Aerial Swarms: Recent Applications and Challenges

(Current Robotics Reports, 2021-07-23) [Article]
Purpose of Review Currently, there is a large body of research on multi-agent systems addressing their different system theoretic aspects. Aerial swarms as one type of multi-agent robotic systems have recently gained huge interest due to their potential applications. However, aerial robot groups are complex multi-disciplinary systems and usually research works focus on specific system aspects for particular applications. The purpose of this review is to provide an overview of the main motivating applications that drive the majority of research works in this field, and summarize fundamental and common algorithmic components required for their development. Recent Findings Most system demonstrations of current aerial swarms are based on simulations, some have shown experiments using few 10 s of robots in controlled indoor environment, and limited number of works have reported outdoor experiments with small number of autonomous aerial vehicles. This indicates scalability issues of current swarm systems in real world environments. This is mainly due to the limited confidence on the individual robot’s localization, swarm-level relative localization, and the rate of exchanged information between the robots that is required for planning safe coordinated motions. Summary This paper summarizes the main motivating aerial swarm applications and the associated research works. In addition, the main research findings of the core elements of any aerial swarm system, state estimation and mission planning, are also presented. Finally, this paper presents a proposed abstraction of an aerial swarm system architecture that can help developers understand the main required modules of such systems.
• #### Two Phases of Monolayer Tantalum Sulfide on Au(111)

(ACS Nano, American Chemical Society (ACS), 2021-07-23) [Article]
We prepared monolayers of tantalum sulfide on Au(111) by evaporation of Ta in a reactive background of H2S. Under sulfur-rich conditions, monolayers of 2H-TaS2 formed, whereas under sulfur-poor conditions TaS2–x with 0 ≤ x ≤ 1 were found. We identified this phase as TaS, a structure that can be derived from 2H-TaS2 by removal of the bottom S layer.
• #### Pushing the Limits of Flexibility and Stretchability of Solar Cells: A Review

(Advanced Materials, Wiley, 2021-07-23) [Article]
Emerging forms of soft, flexible, and stretchable electronics promise to revolutionize the electronics industries of the future offering radically new products that combine multiple functionalities, including power generation, with arbitrary form factor. For example, skin-like electronics promise to transform the human-machine-interface, but the softness of the skin is incompatible with traditional electronic components. To address this issue, new strategies toward soft and wearable electronic systems are currently being pursued, which also include stretchable photovoltaics as self-powering systems for use in autonomous and stretchable electronics of the future. Here recent developments in the field of stretchable photovoltaics are reviewed and their potential for various emerging applications are examined. Emphasis is placed on the different strategies to induce stretchability including extrinsic and intrinsic approaches. In the former case, engineering and patterning of the materials and devices are key elements while intrinsically stretchable systems rely on mechanically compliant materials such as elastomers and organic conjugated polymers. The result is a review article that provides a comprehensive summary of the progress to date in the field of stretchable solar cells from the nanoscale to macroscopic functional devices. The article is concluded by discussing the emerging trends and future developments.
• #### Ambiguities in solvation free energies from cluster-continuum quasichemical theory: lithium cation in protic and aprotic solvents.

(Physical chemistry chemical physics : PCCP, Royal Society of Chemistry (RSC), 2021-07-22) [Article]
Gibbs free energies for Li+ solvation in water, methanol, acetonitrile, DMSO, dimethylacetamide, dimethoxyethane, dimethylformamide, gamma-butyrolactone, pyridine, and sulfolane have been calculated using the cluster-continuum quasichemical theory. With n independent solvent molecules S initial state forming the "monomer" thermodynamic cycle, Li+ solvation free energies are found to be on average 14 kcal mol-1 more positive compared to those from the "cluster" thermodynamic cycle where the initial state is the cluster Sn. We ascribe the inconsistency between the "monomer" and "cluster" cycles mainly to the incorrectly predicted solvation free energies of solvent clusters Sn from the SMD and CPCM continuum solvation models, which is in line with the earlier study of Bryantsev et al., J. Phys. Chem. B, 2008, 112, 9709-9719. When experimental-based solvation free energies of individual solvent molecules and solvent clusters are employed, the "monomer" and "cluster" cycles result in identical numbers. The best overall agreement with experimental-based "bulk" scale lithium cation solvation free energies was obtained for the "monomer" scale, and we recommend this set of values. We expect that further progress in the field is possible if (i) consensus on the accuracy of experimental reference values is achieved; (ii) the most recent continuum solvation models are properly parameterized for all solute-solvent combinations and become widely accessible for testing.
• #### Biomass as source for hydrochar and biochar production to recover phosphates from wastewater: A review on challenges, commercialization, and future perspectives.

(Chemosphere, Elsevier BV, 2021-07-22) [Article]
• #### Decision trees based on 1-consequences

(Discrete Applied Mathematics, Elsevier BV, 2021-07-20) [Article]
In this paper, we study arbitrary infinite binary information systems each of which consists of an infinite set of elements and an infinite set of two-valued non-constant functions (attributes) defined on the set of elements. We consider the notion of a problem over information system, which is described by a finite number of attributes: for a given element, we should determine values of these attributes. As algorithms for problem solving, we study decision trees that use arbitrary attributes from the considered infinite set of attributes and solve the problem based on 1-consequences. In such a tree, we take into account consequences each of which follows from one equation of the kind “attribute value” obtained during the decision tree work and ignore consequences that can be derived only from at least two equations. As time complexity, we study the depth of decision trees. We prove that in the worst case, with the growth of the number of attributes in the problem description, the minimum depth of decision trees based on 1-consequences grows either as a logarithm or linearly.