bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exoplanet cartography using convolutional neural networks
Authors: Meinke K. , Stam D. M. , Visser P. M. 
Published: May 2022

Context. In the near future, dedicated telescopes will observe Earth-like exoplanets in reflected parent starlight, allowing their physical characterization. Because of the huge distances, every exoplanet will remain an unresolved, single pixel, but temporal variations in the pixel’s spectral flux contain information about the planet’s surface and atmosphere.
Aims. We tested convolutional neural networks for retrieving a planet’s rotation axis, surface, and cloud map from simulated single-pixel observations of flux and polarization light curves. We investigated the influence of assuming that the reflection by the planets is Lambertian in the retrieval while in reality their reflection is bidirectional, and the influence of including polarization.
Methods. We simulated observations along a planet’s orbit using a radiative transfer algorithm that includes polarization and bidirectional reflection by vegetation, deserts, oceans, water clouds, and Rayleigh scattering in six spectral bands from 400 to 800 nm, at various levels of photon noise. The surface types and cloud patterns of the facets covering a model planet are based on probability distributions. Our networks were trained with simulated observations of millions of planets before retrieving maps of test planets.
Results. The neural networks can constrain rotation axes with a mean squared error (MSE) as small as 0.0097, depending on the orbital inclination. On a bidirectionally reflecting planet, 92% of ocean facets and 85% of vegetation, deserts, and cloud facets are correctly retrieved, in the absence of noise. With realistic amounts of noise, it should still be possible to retrieve the main map features with a dedicated telescope. Except for face-on orbits, a network trained with Lambertian reflecting planets yields significant retrieval errors when given observations of bidirectionally reflecting planets, in particular, brightness artifacts around a planet’s pole. Including polarization improves the retrieval of the rotation axis and the accuracy of the retrieval of ocean and cloudy map facets.
O’TRAIN: A robust and flexible ‘real or bogus’ classifier for the study of the optical transient sky
Authors: Makhlouf K. , Turpin D. , Corre D. , Karpov S. , Kann D. A. , Klotz A. 
Published: May 2022

Context. Scientific interest in studying high-energy transient phenomena in the Universe has risen sharply over the last decade. At present, multiple ground-based survey projects have emerged to continuously monitor the optical (and multi-messenger) transient sky at higher image cadences and covering ever larger portions of the sky every night. These novel approaches are leading to a substantial increase in global alert rates, which need to be handled with care, especially with regard to keeping the level of false alarms as low as possible. Therefore, the standard transient detection pipelines previously designed for narrow field-of-view instruments must now integrate more sophisticated tools to deal with the growing number and diversity of alerts and false alarms.
Aims. Deep machine learning algorithms have now proven their efficiency in recognising patterns in images. These methods are now used in astrophysics to perform different classification tasks such as identifying bogus from real transient point-like sources. We explore this method to provide a robust and flexible algorithm that could be included in any kind of transient detection pipeline.
Methods. We built a convolutional neural network (CNN) algorithm in order to perform a ‘real or bogus’ classification task on transient candidate cutouts (subtraction residuals) provided by different kinds of optical telescopes. The training involved human-supervised labelling of the cutouts, which are split into two balanced data sets with ‘true’ and ‘false’ point-like source candidates. We tested our CNN model on the candidates produced by two different transient detection pipelines. In addition, we made use of several diagnostic tools to evaluate the classification performance of our CNN models.
Results. We show that our CNN algorithm can be successfully trained on a large and diverse array of images on very different pixel scales. In this training process, we did not detect any strong over- or underfitting with the requirement of providing cutouts with a limited size no larger than 50 × 50 pixels. Tested on optical images from four different telescopes and utilising two different transient detection pipelines, our CNN model provides a robust ‘real or bogus’ classification performance accuracy from 93% up to 98% for well-classified candidates.
The dusty heart of Circinus
Authors: Isbell J. W. , Meisenheimer K. , Pott J.-U. , Stalevski M. , Tristram K. R. W. , Sanchez-Bermudez J. , Hofmann K.-H. , Gámez Rosas V. , Jaffe W. , Burtscher L. , Leftley J. , Petrov R. , Lopez B. , Henning T. , Weigelt G. , Allouche F. , Berio P. , Bettonvil F. , Cruzalebes P. , Dominik C. , Heininger M. , Hogerheijde M. , Lagarde S. , Lehmitz M. , Matter A. , Meilland A. , Millour F. , Robbe-Dubois S. , Schertl D. , van Boekel R. , Varga J. , Woillez J. 
Published: May 2022

Context.Active galactic nuclei play a key role in the evolution of galaxies, but their inner workings and physical connection to the host are poorly understood due to a lack of angular resolution. Infrared interferometry makes it possible to resolve the circumnuclear dust in the nearby Seyfert 2 galaxy, the Circinus Galaxy. Previous observations have revealed complex structures and polar dust emission but interpretation was limited to simple models. The new Multi AperTure mid-Infrared Spectro-Scopic Experiment (MATISSE) makes it possible to image these structures for the first time.Aims.We aim to precisely map the morphology and temperature of the dust surrounding the supermassive black hole through interferometric imaging.Methods.We observed the Circinus Galaxy with MATISSE at the Very Large Telescope Interferometer (VLTI), producing 150 correlated flux spectra and 100 closure phase spectra. The novel inclusion of closure phases makes interferometric imaging possible for the first time. We reconstructed images in theN-band at ∼10 mas resolution. We fit blackbody functions with dust extinction to several aperture-extracted fluxes from the images to produce a temperature distribution of central dusty structures.Results.We find significant substructure in the circumnuclear dust: central unresolved flux of ∼0.5 Jy, a thin disk 1.9 pc in diameter oriented along ∼45°, and a ∼4 × 1.5 pc polar emission extending orthogonal to the disk. The polar emission exhibits patchiness, which we attribute to clumpy dust. Flux enhancements to the east and west of the disk are seen for the first time. We distinguish the temperature profiles of the disk and of the polar emission: the disk shows a steep temperature gradient indicative of denser material; the polar profile is flatter, indicating clumpiness and/or lower dust density. The unresolved flux is fitted with a high temperature, ∼370 K. The polar dust remains warm (∼200 K) out to 1.5 pc from the disk. We attribute approximately 60% of the 12 μm flux to the polar dust, 10% to the disk, and 6% is unresolved; the remaining flux was resolved out. The recovered morphology and temperature distribution resembles modeling of accretion disks with radiation-driven winds at large scales, but we placed new constraints on the subparsec dust.Conclusions.The spatially resolved subparsec features imaged here place new constraints on the physical modeling of circumnuclear dust in active galaxies; we show strong evidence that the polar emission consists of dust clumps or filaments. The dynamics of the structures and their role in the Unified Model remain to be explored.
Institutionalized democracy and the shadow economy in the short- and long-run: empirical analysis from Uganda
Authors: Esaku Stephen 
Published: May 2022

AbstractThis paper investigates the relationship between institutionalized democracy and the shadow economy in both the long- and short-run. Using time series data from Uganda that cover the period from 1991 to 2015, this paper applies autoregressive distributed lag method to investigate this relationship. How democracy affects the shadow economy in less developed countries like Uganda is not well understood. This paper aims to fill the above knowledge gap. The findings show that the shadow economy and institutionalized democracy are negatively correlated in both the short- and long-run. This implies that improvement in institutionalized democracy significantly hinders the rise of shadow activities. This indicates that institutions regulate the conduct of economic agents and determine how entrepreneurs engage in economic activities. Moreover, institutions are crucial in resource allocation which in turn leads to welfare improvement. Improvement in welfare of citizens reduces their incentive to engage in informal sector activities since the formal sector provides the necessary support needed to operate legally. These findings are robust to alternative econometric methods. Two practical implications of these findings stand out. First, these findings indicate that reforming the governance system to facilitate efficient resource allocation could be one way of addressing widespread informality in developing economies. Second, these results also indicate that minimizing informality in the economy should gradually move away from emphasis on tackling proximate causes of informality to democratic reforms that change the authority patterns. In this case institutionalized democracy is another important channel of mitigating the rise of the shadow economy.
Transcriptome analysis of maize pollen grains under drought stress during flowering
Authors: Zhang Yinping , Soualihou Soualiou , Li Juan , Xu Yonghan , Rose Ray J. , Ruan Yong-Ling , Li Jincai , Song Youhong 
Published: May 2022

Drought stress is detrimental to male reproduction in maize (Zea mays L.), largely through reducing the quantity and quality of pollen grains. However, transcriptional response of maize pollen grains to drought stress has not been well documented. We compared pollen gene expression for a maize hybrid (ZhongDan909) under well-watered and drought-stress conditions, based on RNA-Seq validated by quantitative real-time PCR analysis. Expression of 6424 genes and 1302 transcripts was altered in pollen grains of maize subjected to 7 days of drought during flowering. Gene Ontology annotations showed 308 differentially expressed genes, annotated and classified into 50 primary functional categories. Kyoto Encyclopedia of Genes and Genomes analyses revealed 44 differentially expressed genes in nine metabolic pathways. In relation to carbohydrate metabolism pathways, there was downregulation of a polygalacturonase gene, which could reduce cell wall lysis in early pollen germination, and an increase in callose synthase transcripts along with reduced cellulase transcripts. These altered gene expressions responsible for cell wall integrity may inhibit the initiation of pollen tube growth. The onset of tube growth could be further impeded by observed changes in gene expression that potentially influence hormone metabolism (including downregulation of AUXIN RESPONSE FACTOR 18 and EIN3-BINDING F-BOX), reduce mitochondrial function, and alter protein translation. Genes with potential roles in adaptation were also altered in their transcript levels. These included genes encoding the upregulated transcription factor ZmNF-YC2, and the downregulated ZmbHLH13, a negative regulator of jasmonic acid responses. The upregulated flavin enzyme gene DIHYDROLIPOYL DEHYDROGENASE 1, associated with increased levels of reactive oxygen species, is of interest in relating redox homeostasis to stress adaptation. Overall, the analyses identified a suite of genes involved in the development of pollen grains and tubes and responsive to drought stress. The findings enhance understanding of the gene networks underlying compromised pollen viability under drought stress.
Full adoption of the most effective strategies to mitigate methane emissions by ruminants can help meet the 1.5 °C target by 2030 but not 2050
Authors: Arndt Claudia , Hristov Alexander N. , Price William J. , McClelland Shelby C. , Pelaez Amalia M. , Cueva Sergio F. , Oh Joonpyo , Dijkstra Jan , Bannink André , Bayat Ali R. , Crompton Les A. , Eugène Maguy A. , Enahoro Dolapo , Kebreab Ermias , Kreuzer Michael , McGee Mark , Martin Cécile , Newbold Charles J. , Reynolds Christopher K. , Schwarm Angela , Shingfield Kevin J. , Veneman Jolien B. , Yáñez-Ruiz David R. , Yu Zhongtang 
Published: May 2022

Significance
Agricultural methane emissions must be decreased by 11 to 30% of the 2010 level by 2030 and by 24 to 47% by 2050 to meet the 1.5 °C target. We identified three strategies to decrease product-based methane emissions while increasing animal productivity and five strategies to decrease absolute methane emissions without reducing animal productivity. Globally, 100% adoption of the most effective product-based and absolute methane emission mitigation strategy can meet the 1.5 °C target by 2030 but not 2050, because mitigation effects are offset by projected increases in methane. On a regional level, Europe but not Africa may be able to meet their contribution to the 1.5 °C target, highlighting the different challenges faced by high- and middle- and low-income countries.
Information geometry, Pythagorean-theorem extension, and Euclidean distance behind optical sensing via spectral analysis
Authors: Zheltikov A M 
Published: May 2022

Abstract
We present an information-geometric perspective on a generic spectral-analysis task pertaining to a vast class of optical measurements in which a parameter θ needs to be evaluated from θ-dependent spectral features in a measurable optical readout. We show that the spectral shift and line broadening driven by small Δθ variations can be isolated as orthogonal components in a Pythagorean-theorem extension for a Euclidean distance in the space of probability distributions, representing the Δθ-induced information gain, expressible via the relative entropy and the pertinent Fisher information. This result offers important insights into the limits of optical signal analysis, as well as into the ultimate spectral resolution and the limiting sensitivity of a vast class of optical measurements. As one example, we derive a physically transparent closed-form analytical solution for the information-theory bound on the precision of all-optical temperature sensors based on color centers in diamond.
Near field radio link design in fat phantom for Wireless Capsule Endoscopy application
Authors: Kamaruddin Nur Amalina , Kamardin Kamilia , Yamada Yoshihide , Zainudin Norsiha , Arima Takuji , Michishita Naobumi , Takahashi Masaharu 
Published: May 2022

Abstract
Medical devices such as Wireless Capsule Endoscopy (WCE) that need wireless imaging and monitoring, operating at 402 MHz, is considered to be in the near field region due to the distance being shorter than the wavelength. In this paper, the radio link calculation method in the near field region is investigated. Normal Mode Helical Antenna (NMHA) is used as the transmitter antenna which is placed inside of a fat phantom of 11.6 F/m and the receiver antenna at distance 0.1 to 1.0 m apart. For link budget establishment, parameters such as power density, W and receiver antenna effective area, Ae
are investigated through electromagnetic simulation. The distance dependency of W is examined and the result of W∝ 1/(distance)2 is obtained. The relation of Ae
of the receiver antenna is found to be the size of the cross-section area of the antenna. A radio link equation is formed by employing W, Ae
and other propagation loss factors of a medium and is then compared with the power received, PR
and S21
obtained from simulation. The agreement between calculated and simulated results shows that this equation can be used in the near field region.
Biocompatible Sago Aerogel Material as A Substrate for Antenna Application
Authors: Adnan M A , Kamilia K , Yamada Y , Idris I H , Ali A A , Hamdan H. 
Published: May 2022

Abstract
This paper presents a patch antenna that operates at 2.4 GHz for body communication applications. New biocompatible material is proposed named Sago Aerogel is used as the antenna substrate. As a new substrate material is proposed, a simple patch antenna with a total size of substrate size of 60 mm × 66.2 mm × 1.6 mm size designed and simulated. The antenna performances in terms of S11 value, radiation pattern, gain, and input impedance are studied and discussed.
Focal Region Ray Tracing for Slanted Incident Rays on Spherical Reflector Antenna
Authors: Arjunaidi Ayuni Afiqah , Yamada Yoshihide , Kamardin Kamilia 
Published: May 2022

Abstract
Multi beam antenna system is required at base station for fifth-generation (5G) mobile communication and also to cover large portions of field of view for the satellite antenna. A spherical reflector antenna is promising to give high gain directivity of each independent beams for its multiple beam capabilities. The study of the feed elements system is carried out by analysing the focus of slanted incident rays in receiving mode from 0° to 30° at step angle 10°. Simple analytical equations are derived to find the incident and reflected rays. This focal region of spherical reflector is studied in MATLAB program. Accuracy of the MATLAB results are validated by examining the focal region using an electromagnetic simulator, FEKO. The locus of feed of spherical reflector antenna for certain angles of the incident rays are presented in this study.
Fabrication and characterisation of Frequency Selective Surface (FSS) for Terahertz Sensing Application
Authors: Ishak N S , Zainal N , Seman F C , Shah S M 
Published: May 2022

Abstract
A frequency selective surface (FSS) structure based on a circular slot with 28 to 31 μm was fabricated using Electron Beam Lithography combined with wet etching technique on a 400 μm thick quartz substrate. The circular slot pattern, designed using the CST software, was transferred during the Electron Beam (EBL) exposure with 100 kV voltage acceleration, 2 nA of e-beam current, and line dosage of 1000 μC2. A 0.5 μm thick aluminium layer was deposited on a quartz substrate using the thermal evaporator technique. The aluminium thickness was confirmed by laser microscope and surface profiler measurement. The investigation shows that 20 seconds is the optimal etching time for producing the desired FSS circular slot structure compared to 40 and 60 seconds. The fabricated samples surface metrology was examined using an optical microscope, Field Emission Scanning Electron Microscope (FESEM) and Atomic Force Microscope (AFM). The material compositions of the samples were confirmed by using the Energy Dispersive X-ray (EDX) measurement. Results show that, on average, there are ±1.5 μm of tolerance produced for fabricated sample size on the circular slot pattern compared to the CST simulation results. FSS performance slightly shifted in the frequency from actual 1.80 THz to 1.79 THz, whereas the transmission magnitude has increased by 0.03 from 0.91 to 0.94.
Near Field on Inductor Loops for Inductive Couple Fed Antenna
Authors: Azmi N Q , Murad N A , Samsuri N A , Tanvir A R , Nizam A A Z A 
Published: May 2022

Abstract
This paper presents an evaluation on the near field of square loop and circular loop for inductive couple fed RFID Tag antenna. The loop is simulated with different diameter and width The turns number (N) of the loop is varies up to three number of turns for each loop length. The magnetic fields and inductance are simulated to estimate the signal strength that can be coupled to the tag antenna. To evaluate the performance, the inductive feeding loop is designed to operate at RFID UHF band (860 MHz - 960 MHz) and simulated using CST software. It is confirmed that 6 mm loop length of the square and circular loop has higher magnetic field values as the surface area of the loop is bigger. The loop with different overall dimension gives out different reactance, inductance and magnetic field, dipole antenna, CST, and loop antenna.
Design of a Flexible T-Matched Feed UHF RFID Tag Antenna
Authors: Miswadi NF. , Abd Rahman NH , Subahir S. , Aris M.A. , Awang RA , Lim E.H. 
Published: May 2022

Abstract
A flexible radio frequency identification (RFID) tag antenna with a T-match feeder is proposed in this paper. The T-match feed acts as the conjugate network matching of the tag antenna and 0.99 of power transfer coefficient was achieved. By incorporating a meander line and capacitive tip loading technique, the compact size is realized with a wide bandwidth of 44MHz that can cover the RFID spectrum allocated for the Malaysia region, from 919 to 923 MHz. The proposed antenna is printed on the flexible polyethene terephthalate (PET) substrate with a dimension of 90mm × 24mm × 0.143mm. By employing 4W EIRP power, the detection distance of 29.15m in free space. The proposed meandered line and capacitive tip loading tag antenna with T-match feed line is beneficial to be part of the RFID systems because of their compactness, wide bandwidth and high-power transfer coefficient.
Utilizing Logistic Map to Enhance the Population Diversity of PSO
Authors: Ajibade S M , Chweya R , Ogunbolu M O , Fadipe S R 
Published: May 2022

Abstract
Particle swarm optimization (PSO) is a high-quality, nature-inspired global optimization algorithm that can be applied to a variety of real-world optimization problems. PSO, on the other hand, has some flaws, such as slow convergence, premature convergence, and the ability to become stuck at local optimum solutions. This research aims to address the issue of population diversity in the PSO search process, which leads to premature convergence. As a result, in this study, a method is introduced to PSO in order to avoid early stagnation, which leads to premature convergence. A chaotic dynamic weight particle swarm optimization (CTPSOA) is proposed, in which a chaotic logistic map is delivered to increase the population range within the PSO search technique by editing the inertia weight of PSO to avoid premature convergence. This study also looks into the overall performance and viability of the proposed CTPSOA as a set of function selection rules for solving optimization issues. There are eight traditional benchmark functions that are used to assess the overall results and obtain the accuracy of the proposed (CTPSOA) algorithms when compared to a few other meta-heuristics optimization rules. The test results reveal that the CTPSOA outperforms other meta-heuristics algorithms in solving optimization problems by 85% and has established itself as a reliable and superior metaheuristics algorithm for feature selection.
Galactic cosmic rays above the Earth’s atmosphere
Authors: Buchvarova Marusya 
Published: May 2022

AbstractGalactic cosmic rays (GCRs) originate from sources outside the solar system and reach the Earth’s environment from all directions. More than 100 years after the first detection of cosmic rays, the origin of high-energy cosmic rays is still a mystery. Although our knowledge of the origin and propagation of cosmic rays is relatively limited, we can study the radiation conditions in the near-Earth space environment in more detail. The origin, composition, and energy spectra of cosmic rays are briefly discussed in this paper. A brief review of the transport of galactic cosmic rays in the heliosphere is given. The geomagnetic effects on galactic cosmic rays and the atmospheric interactions of primary particles are also discussed in the paper.