bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new generalized θ-conformable calculus and its applications in mathematical physics
Authors: Hyder Abd-Allah , Soliman Ahmed H 
Published: November 2020

Abstract
In this work, a new generalized concept of conformable derivative is given and named generalized θ–conformable derivative (GTCD). Several properties are studied such as the chain rule, the quotient rule, the product rule, the Rolle’s theorem, the mean value theorem and the fundamental theorems of calculus. Also, the geometrical and physical interpretations of the GTCD are presented. It is very easy to see that the GTCD is comprehensive and includes many past derivatives as special cases. An application of the generalized θ–conformable derivatives (GTCDs) is presented along with the

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–approach to construct a novel gathering of exact solutions for the nonlinear (2+1)-dimensional biological population model (BPM) involving GTCDs. Moreover, some comparisons and graphical interpretations are given to support our results related to the (2+1)-dimensional BPM. All acquired results regarding the GTCD show its validity to applying in many problems in mathematical physics, engineering, biology and others.
Bio-inspired compact swarms of unmanned aerial vehicles without communication and external localization
Authors: Petráček Pavel , Walter Viktor , Báča Tomáš , Saska Martin 
Published: November 2020

Abstract
This article presents a unique framework for deploying decentralized and infrastructure-independent swarms of homogeneous aerial vehicles in the real world without explicit communication. This is a requirement in swarm research, which anticipates that global knowledge and communication will not scale well with the number of robots. The system architecture proposed in this article employs the ultraviolet direction and ranging technique to directly perceive the local neighborhood for direct mutual localization of swarm members. The technique allows for decentralization and high scalability of swarm systems, such as can be observed in fish schools, bird flocks, or cattle herds. The bio-inspired swarming model that has been developed is suited for real-world deployment of large particle groups in outdoor and indoor environments with obstacles. The collective behavior of the model emerges from a set of local rules based on direct observation of the neighborhood using onboard sensors only. The model is scalable, requires only local perception of agents and the environment, and requires no communication among the agents. Apart from simulated scenarios, the performance and usability of the entire framework is analyzed in several real-world experiments with a fully-decentralized swarm of unmanned aerial vehicles (UAVs) deployed in outdoor conditions. To the best of our knowledge, these experiments are the first deployment of decentralized bio-inspired compact swarms of UAVs without the use of a communication network or shared absolute localization. The entire system is available as open-source at https://github.com/ctu-mrs.
Flow turning effect and laminar control by the 3D curvature of leading edge serrations from owl wing
Authors: Muthuramalingam Muthukumar , Talboys Edward , Wagner Hermann , Bruecker Christoph 
Published: November 2020

Abstract
This work describes a novel mechanism of laminar flow control of straight and backward swept wings with a comb-like leading edge (LE) device. It is inspired by the LE comb on owl feathers and the special design of its barbs, resembling a cascade of complex 3D-curved thin finlets. The details of the geometry of the barbs from an owl feather were used to design a generic model of the comb for experimental and numerical flow studies with the comb attached to the LE of a flat plate. Due to the owls demonstrating a backward sweep of the wing during gliding and flapping from live recordings, our examinations have also been carried out at differing sweep angles. The results demonstrate a flow turning effect in the boundary layer inboards, which extends downstream in the chordwise direction over distances of multiples of the barb lengths. The inboard flow-turning effect described here, counter-acts the outboard directed cross-span flow typically appearing for backward swept wings. This flow turning behaviour is also shown on SD7003 airfoil using precursory LES investigations. From recent theoretical studies on a swept wing, such a way of turning the flow in the boundary layer is known to attenuate crossflow instabilities and delay transition. A comparison of the comb-induced cross-span velocity profiles with those proven to delay laminar to turbulent transition in theory shows excellent agreement, which supports the laminar flow control hypothesis. Thus, the observed effect is expected to delay transition in owl flight, contributing to a more silent flight.
A new estimate for oceanic precipitation amount and distribution using complementary precipitation observations from space and comparison with GPCP
Authors: Behrangi Ali , Song Yang 
Published: November 2020

Abstract
This study produces near global (81°S/N) spatial and seasonal maps of oceanic precipitation rate using complementary information from advanced precipitation measuring sensors and provides an independent reference that can be used to assess current precipitation products. The Merged CloudSat, Tropical Rainfall Measuring Mission (TRMM), and Global Precipitation Measurement (GPM) (MCTG) estimate uses light rainfall and snowfall estimates from CloudSat and merges them with the combined radar-radiometer products available from the TRMM and the GPM mission. The merging process is performed at grid level and for each season, so maps of the merged products can be constructed. MCTG was then compared with the most recent Global Precipitation Climatology Project (GPCP) product (V2.3) to identify regional, seasonal, and annual differences between the two products. Several areas of major differences were highlighted, among those are regions near 5°N/S, 20°N/S, 40°N/S and 60°N/S. These regions also show seasonal variations in the magnitude and exact location of the differences. The largest differences between GPCP and MCTG occur around 40°S and 60°S, showing an under- and overestimation of MCTG, respectively. Overall, MCTG suggests that GPCP underestimates the annual oceanic precipitation rate by 9.03%, while seasonal rates are underestimated by 7.14%, 9.71%, 9.96%, and 9.73% for winter, spring, summer, and fall, respectively. Such differences in global oceanic precipitation rates need to be considered in the future updates in water and energy budget calculations and in future updates of GPCP.
Caspian Sea is eutrophying: the alarming message of satellite data
Authors: Modabberi Anahita , Noori Roohollah , Madani Kaveh , Ehsani Amir Houshang , Danandeh Mehr Ali , Hooshyaripor Farhad , Kløve Bjørn 
Published: November 2020

Abstract
The competition over extracting the energy resources of the Caspian Sea together with the major anthropogenic changes in the coastal zones have resulted in increased pollution and environmental degradation of the sea. We provide the first evaluation of the spatiotemporal variation of chlorophyll-a (Chl-a) across the Caspian Sea. Using remotely sensed data from 2003 to 2017, we found that the Caspian Sea has suffered from a growing increase in Chl-a, especially in warmer months. The shallow parts of the sea, near Russia and Kazakhstan, especially where the Volga and Terek rivers discharge large nutrient loads (nitrogen- and phosphorus-rich compounds) into the sea, have experienced the highest variations in Chl-a. The Carlson’s trophic state index showed that during the study period, on average, about 12%, 26%, and 62% of the Caspian Sea’s area was eutrophic, mesotrophic, and oligotrophic, respectively. The identified trends reflect an increasing rate of environmental degradation in the Caspian Sea, which has been the subject of conflict among its littoral states that since the collapse of the Soviet Union have remained unable to agree on a legal regime for governing the sea and its resources.
Experimental investigation of Kramers–Kronig relations in chiral metasurfaces with reduced rotational symmetry
Authors: Singh Leeju , David Epstein Eliav , Cheskis Dima , Sternklar Shmuel , Gorodetski Yuri 
Published: November 2020

Abstract
We examine the Kramers–Kronig relations between the circular dichroism and the optical rotation dispersion in the k-space obtained from a chiral metasurface with a reduced rotational symmetry. We operate a leakage-radiation microscopy system to probe the near-field plasmonic modes and measure the polarization effects of the grating. By using our system we were able to capture and analyze the plasmonic modes at both air/gold and gold/glass interfaces. The k-space mapping of the chirality parameters allows us to fully analyze the optical activity of the metasurface. We experimentally find that the reduction in rotational symmetry affects the locality condition which unavoidably leads to the deviation from the Kramers–Kronig relation.
Phase transformation of a vortex beam in a liquid-based inferior mirage
Authors: Cisowski Claire M , Correia Ricardo R B 
Published: November 2020

Abstract
We study how a liquid-based inferior mirage, obtained by layering distilled water and ethanol, transforms the phase structure of a light beam possessing a helical wave front. An inferior mirage amounts for one total internal reflection, which effectively reverses the handedness of the wave front. We show that this transformation is accompanied by smooth unidirectional astigmatic changes and variations of the non-canonical strength of the phase singularity nested in the beam. A skew in the beam intensity distribution is observed where the phase singularity is inverted and allows the direct measurement of the topological charge of the beam. Freely propagating, partially inverted beams possessing spatially varying orbital fluxes can be obtained at the exit plane of the solution by adjusting the incidence conditions of the beam. This work lays the foundations for phase engineering of light beams in liquid-based optical mirages.
Two-dimensional materials applied for room-temperature thermoelectric photodetectors
Authors: Wang Jiaqi , Xie Zhemiao , Yeow John T W 
Published: November 2020

Abstract
Due to the practical demand in many fields, room-temperature photodetectors in mid/long-wavelength and terahertz ranges have attracted much attention. Photothermoelectric (PTE) detectors based on photothermal conversion and thermoelectric effect can realize ultra-broadband detection of a photon without external bias. In recent years, two-dimensional (2D) materials open up revolutionary opportunities in rapid and sensitive photodetection by virtue of their remarkable electronic and optical properties. Here, we provide a brief review of state-of-the-art photodetectors based on PTE effect and 2D materials. It is worth noting that emerging PTE detectors based on 2D materials, including graphene, transition metal dichalcogenides (TMDCs), black phosphorus (BP) and MXenes, are proposed systematically. Next, we will discuss the existing challenges and prospects in PTE detectors, followed by a conclusion of this review.
Electrical transport properties and impedance analysis of Au/ZnO nanorods/ITO heterojunction device
Authors: Guruprasad Kuppuswamy , Marappan Gobinath , Elangovan Surya , Velappa Jayaraman Surya , Kamala Bharathi K , Venugopal Gunasekaran , Di Natale Corrado , Sivalingam Yuvaraj 
Published: November 2020

Abstract
Our work involves the growth of well aligned vertical nanorods of ZnO on transparent indium doped tin oxide (ITO) conductive substrate and fabrication of Au/ZnO Nanorods/ITO Heterojunction device. The observation of non-ideal diode current density-voltage (J-V) characteristics of the device has been evaluated with various conduction mechanisms [Ohmic, space-charge limited conduction (SCLC)]. The charge carrier mobility is estimated to be ∼0.05 cm2/Vs. The presence of deep level defects in the ZnO nanorods is accountable for these two different transport mechanisms and it is backed by photoluminescence, distinctly. The estimated density of deep trap states is ntrap ∼ 5.76 × 1013 cm−3. The charge carrier density and built-in potential of this device are obtained from electrochemical impedance spectroscopy (EIS). The average work function of vertical ZnO nanorods is found out to be ∼4.93 eV. Henceforth, our results explain the charge transport mechanism which plays a key role in optoelectronic based devices for various applications.
Spatial allocation without spatial recruitment in bumblebees
Authors: Incorvaia Darren C , Hintze Arend , Dyer Fred C 
Published: November 2020

AbstractAny foraging animal is expected to allocate its efforts among resource patches that vary in quality across time and space. For social insects, this problem is shifted to the colony level: the task of allocating foraging workers to the best patches currently available. To deal with this task, honeybees rely upon differential recruitment via the dance language, while some ants use differential recruitment on odor trails. Bumblebees, close relatives of honeybees, should also benefit from optimizing spatial allocation but lack any targeted recruitment system. How bumblebees solve this problem is thus of immense interest to evolutionary biologists studying collective behavior. It has been thought that bumblebees could solve the spatial allocation problem by relying on the summed individual decisions of foragers, who occasionally sample and shift to alternative resources. We use field experiments to test the hypothesis that bumblebees augment individual exploration with social information. Specifically, we provide behavioral evidence that, when higher-concentration sucrose arrives at the nest, employed foragers abandon their patches to begin searching for the better option; they are more likely to accept novel resources if they match the quality of the sucrose solution experienced in the nest. We explored this strategy further by building an agent-based model of bumblebee foraging. This model supports the hypothesis that using social information to inform search decisions is advantageous over individual search alone. Our results show that bumblebees use a collective foraging strategy built on social modulation of individual decisions, providing further insight into the evolution of collective behavior.
Treed distributed lag nonlinear models
Authors: Mork Daniel , Wilson Ander 
Published: November 2020

Summary
In studies of maternal exposure to air pollution, a children’s health outcome is regressed on exposures observed during pregnancy. The distributed lag nonlinear model (DLNM) is a statistical method commonly implemented to estimate an exposure–time–response function when it is postulated the exposure effect is nonlinear. Previous implementations of the DLNM estimate an exposure–time–response surface parameterized with a bivariate basis expansion. However, basis functions such as splines assume smoothness across the entire exposure–time–response surface, which may be unrealistic in settings where the exposure is associated with the outcome only in a specific time window. We propose a framework for estimating the DLNM based on Bayesian additive regression trees. Our method operates using a set of regression trees that each assume piecewise constant relationships across the exposure–time space. In a simulation, we show that our model outperforms spline-based models when the exposure–time surface is not smooth, while both methods perform similarly in settings where the true surface is smooth. Importantly, the proposed approach is lower variance and more precisely identifies critical windows during which exposure is associated with a future health outcome. We apply our method to estimate the association between maternal exposures to PM$_{2.5}$ and birth weight in a Colorado, USA birth cohort.
A synopsis of the androgynous species ofCarexsubgenusVignea(Cyperaceae) in South America
Authors: Jiménez-Mejías Pedro , Martín-Bravo Santiago , Márquez-Corro José Ignacio , Donadío Sabina , Roalson Eric H , Naczi Robert F C 
Published: November 2020

AbstractThis is the first work of a series of thorough studies into the taxonomy and systematics of Carex in South America. Here, we present the systematic placement, biogeographic insights, taxonomic accounts, formal typifications and summarized distributions for the 24 species of Carex subgenus Vignea with androgynous spikes in the continent. We performed a phylogenetic study using the barcode markers ETS, ITS and matK to check the placement of 22 of these species on a previous tree with &gt; 1000 Carex spp. We examined &gt; 600 specimens from 38 herbaria and conducted an exhaustive nomenclatural survey consulting all pertinent literature. South American androgynous species of subgenus Vignea are grouped in seven distinct lineages, corresponding with the same number of inferred colonizations. Most groups seem to have colonized South America during the Plio-Pleistocene, except for species of section Bracteosae, a local radiation that dates back to the Late Miocene. All colonizations by native species seem to have originated from North America. The two putatively introduced taxa are western Palaearctic species. An identification key is provided for the studied species. We make 19 new typifications and a new species (Carex pedicularis) is described.
Spatiotemporal features of β-γ phase-amplitude coupling in Parkinson’s disease derived from scalp EEG
Authors: Gong Ruxue , Wegscheider Mirko , Mühlberg Christoph , Gast Richard , Fricke Christopher , Rumpf Jost-Julian , Nikulin Vadim V , Knösche Thomas R , Classen Joseph 
Published: November 2020

Abstract
Abnormal phase-amplitude coupling between β and broadband-γ activities has been identified in recordings from the cortex or scalp of patients with Parkinson’s disease. While enhanced phase-amplitude coupling has been proposed as a biomarker of Parkinson’s disease, the neuronal mechanisms underlying the abnormal coupling and its relationship to motor impairments in Parkinson’s disease remain unclear. To address these issues, we performed an in-depth analysis of high-density EEG recordings at rest in 19 patients with Parkinson’s disease and 20 age- and sex-matched healthy control subjects. EEG signals were projected onto the individual cortical surfaces using source reconstruction techniques and separated into spatiotemporal components using independent component analysis. Compared to healthy controls, phase-amplitude coupling of Parkinson’s disease patients was enhanced in dorsolateral prefrontal cortex, premotor cortex, primary motor cortex and somatosensory cortex, the difference being statistically significant in the hemisphere contralateral to the clinically more affected side. β and γ signals involved in generating abnormal phase-amplitude coupling were not strictly phase-phase coupled, ruling out that phase-amplitude coupling merely reflects the abnormal activity of a single oscillator in a recurrent network. We found important differences for couplings between the β and γ signals from identical components as opposed to those from different components (originating from distinct spatial locations). While both couplings were abnormally enhanced in patients, only the latter were correlated with clinical motor severity as indexed by part III of the Movement Disorder Society Unified Parkinson’s Disease Rating Scale. Correlations with parkinsonian motor symptoms of such inter-component couplings were found in premotor, primary motor and somatosensory cortex, but not in dorsolateral prefrontal cortex, suggesting motor domain specificity. The topography of phase-amplitude coupling demonstrated profound differences in patients compared to controls. These findings suggest, first, that enhanced phase-amplitude coupling in Parkinson’s disease patients originates from the coupling between distinct neural networks in several brain regions involved in motor control. Because these regions included the somatosensory cortex, abnormal phase-amplitude coupling is not exclusively tied to the hyperdirect tract connecting cortical regions monosynaptically with the subthalamic nucleus. Second, only the coupling between β and γ signals from different components appears to have pathophysiological significance, suggesting that therapeutic approaches breaking the abnormal lateral coupling between neuronal circuits may be more promising than targeting phase-amplitude coupling per se.
Facilitating Water electrolysers for electricity-grid services in Europe through establishing standardized testing protocols
Authors: You Shi , Reissner Regine , Imboden Christoph , Bourasseau Cyril , Marcuello Pablo , Greenhalgh Daniel , Green Ben , Abadía Laura , Gil Vanesa , Bornstein Marius , Zong Yi , Chen Xu , Træholt Chresten 
Published: November 2020

Abstract
Electrolysers, which convert electricity into hydrogen, have the potential to offer a variety of electrical-grid services, therefore facilitating the integration of intermittent renewables into electrical grids. Among various activities that aim to unlock this hidden value, the 3-year European Union project QualyGridS launched in 2017 aims to establish standardized testing protocols for electrolysers to perform electricity-grid services. This paper shares experience and intermediate results of QualyGridS with respect to the testing protocols, test benches and testing results. The results of this work facilitate mutual understanding between the electricity industry and the hydrogen industry, support further development of the cross-sector testing standards, guide the design and selection of grid-service-oriented electrolyser applications and foster the transition towards a fossil-free-energy future based on high shares of hydrogen and other renewable solutions.
Sulphite measurement and its influence on Hg behaviour in wet-limestone flue-gas desulphurization
Authors: Masoomi Ida , Bruttel Sophia , Schmid Marc Oliver , Scheffknecht Günter 
Published: November 2020

Abstract
The most abundant and typical reducing agent for oxidized mercury in the slurry of wet flue-gas desulphurization (FGD) is the absorbed sulphur dioxide (SO2), which is present as different species of bisulphite or sulphite, depending on the pH of the slurry. In this study, two different measurement principles for continuous sulphite measurement in the slurry of lab-scale FGD were investigated to check their feasibility to be implemented in a wet FGD. The first method is based on light absorbance at the characteristic wavelength of sulphite measurement using a spectrophotometer and, in the second method, sulphite is measured as sulphur dioxide using a gas sensor. In addition, the correlation of sulphite concentration and mercury (Hg) in the slurry can be shown by measuring sulphite semi-continuously. It was concluded that using a spectrophotometer leads to distorted results. In contrast, measuring sulphite as SO2 in the gas phase proved to be more selective. The implementation of the measurement technique in the lab-scale FGD showed promising results for sulphite measurement. Thus, the correlation of Hg and sulphite concentration could be shown at different synthetic slurries containing different halides. Using a slurry without halides demonstrated the ambivalent influence of sulphite in reactions involving Hg, in which sulphite acts as a ligand for Hg complexes as well as a reducing agent, depending on the existing concentration. However, in the presence of halides, the role of sulphite was less significant.