bluuebunny/crossref_metadata_2025 huggingface dataset:
Dearomatization of 3-cyanoindoles by (3 + 2) cycloaddition: from batch to flow chemistry
Authors: Manneveau Maxime , Tanii Saori , Gens Fanny , Legros Julien , Chataigner Isabelle
Published: April 2020

(3 + 2) Dearomatizing cycloaddition of 3-cyanoindoles occurs in smooth conditions with a non-stabilized azomethine ylide, to yield tricyclic indolines in only 1 min under microflow conditions using 3 equiv of the dipole precursorvs.6 equiv. in a batch reactor.
Highly elastic, strong, and reprocessable cross-linked polyolefin elastomers enabled by boronic ester bonds
Authors: Yang Fei , Pan Li , Ma Zhe , Lou Yahui , Li Yuanyuan , Li Yuesheng
Published: April 2020

Despite the development of new catalysts and synthetic strategies to prepare polyolefin elastomers (POEs), less progress has been made in balancing their elastomeric properties with processability and resistance to heat and solvents.
Enhanced energy efficiency for the complete mineralization of diclofenac by self-sequential ultrasound enhanced ozonation
Authors: Chen Zhen , Yang Shewei , Wang Yonghong , Zhu Mingshan , Wei Chaohai
Published: April 2020

Self-sequential ultrasound enhanced ozonation is a feasible energy-saving solution for the diclofenac mineralization, which is due to the combination of oxidative decomposition ability of ozone and continuous mineralization ability of ˙OH.
Developing an effective polarizable bond method for small molecules with application to optimized molecular docking
Authors: Duan Guanfu , Ji Changge , Zhang John Z. H.
Published: April 2020

Electrostatic interaction plays an essential role in protein–ligand binding.
A facile, practical and metal-free microwave-assisted protocol for mono- and bis-[1,2,4]triazolo[1,5-a]pyridines synthesis utilizing 1-amino-2-imino-pyridine derivatives as versatile precursors
Authors: Ibrahim Hamada Mohamed , Behbehani Haider , Ahmed Arafa Wael Abdelgayed
Published: April 2020

A novel and highly efficient, protocol for synthesizing mono- and bis-[1,2,4]triazolo[1,5-a]pyridines has been established utilizing the readily attainable 1-amino-2-imino-pyridines and microwave irradiation as green energy source.
Crystallographic facet selective HER catalysis: exemplified in FeP and NiP2 single crystals
Authors: Owens-Baird Bryan , Sousa Juliana P. S. , Ziouani Yasmine , Petrovykh Dmitri Y. , Zarkevich Nikolai A. , Johnson Duane D. , Kolen'ko Yury V. , Kovnir Kirill
Published: April 2020

The effect of the crystal structure of ordered transition-metal phosphide catalysts on the hydrogen-evolution reaction is investigated using single crystals of iron-phosphide (FeP) and monoclinic nickel-diphosphide (m-NiP2).
Tuning reactivity layer-by-layer: formic acid activation on Ag/Pd(111)
Authors: Karatok Mustafa , Duanmu Kaining , O'Connor Christopher R. , Boscoboinik Jorge Anibal , Sautet Philippe , Madix Robert J. , Friend Cynthia M.
Published: April 2020

Modified electronic structure of Ag monolayer on Pd(111) enhances reactivity of Ag towards formic acid.
Self-assembly and intracellular delivery of DNA by a truncated fragment derived from theTrojanpeptidePenetratin
Authors: Mello Lucas R. , Hamley Ian W. , Castelletto Valeria , Garcia Bianca B. M. , Lourenço Thiago C. , Vassiliades Sandra V. , Alves Wendel A. , Han Sang W. , Silva Emerson R.
Published: April 2020

A heptamer containing the longest noncationic amino acid sequence ofPenetratinis shown to form peptiplexes with DNA. The structure is characterized from molecular to nanoscopic scale and peptiplexes are shown to assist intracell delivery of DNA.
Self similarity of liquid droplet coalescence in a quasi-2D free-standing liquid-crystal film
Authors: Klopp Christoph , Trittel Torsten , Stannarius Ralf
Published: April 2020

Flat droplets coalescing on smectic free-standing films show self-similar dynamics.
High-performance silicon nanocomposite based ionic actuators
Authors: Lu Chao , Huang Quanzhang , Chen Xi
Published: April 2020

Ultrahigh ion-sensitive silicon nanocomposites are designed for powerful ionic actuators with highly efficient electromechanical conversion and long cycling life.
Plasma-induced on-surface sulfur vacancies in NiCo2S4 enhance the energy storage performance of supercapatteries
Authors: Wang Xiaoxiang , Zhou Rusen , Zhang Chunmei , Xi Shibo , Jones Michael W. M. , Tesfamichael Tuquabo , Du Aijun , Gui Ke , Ostrikov Kostya (Ken) , Wang Hongxia
Published: April 2020

Accurate tuning sulfur vacancy of NiCo2S4 nanoparticles enabled by plasma treatment provides a novel and efficient approach to enhance electrochemical performance of supercapattery.
Restricted lithiation into a layered V2O5 cathode towards building “rocking-chair” type Li-ion batteries and beyond
Authors: Natarajan Subramanian , Kim Sang-Jae , Aravindan Vanchiappan
Published: April 2020

Recent research progress on the full-cell evaluation of V2O5 with various types of anodes is discussed in detail.
Activation of a Pt-loaded Pb2Ti2O5.4F1.2 photocatalyst by alkaline chloride treatment for improved H2 evolution under visible light
Authors: Wakayama Haruki , Kato Kosaku , Kashihara Kodai , Uchiyama Tomoki , Miyoshi Akinobu , Nakata Hiroko , Lu Daling , Oka Kengo , Yamakata Akira , Uchimoto Yoshiharu , Maeda Kazuhiko
Published: April 2020

Improved activity of visible-light H2 evolution was reported using NaCl–CsCl-treated Pb2Ti2O5.4F1.2 photocatalyst, along with the underlying mechanism of activation.
Electrospun polyfunctional conductive anisotropic Janus-shaped film, derivative 3D Janus tube and 3D plus 2D complete flag-shaped structures
Authors: Qi Haina , Ma Qianli , Xie Yunrui , Song Yan , Tian Jiao , Yu Wensheng , Dong Xiangting , Li Dan , Liu Guixia , Yu Hui
Published: April 2020

Anisotropic conductive–magnetic–luminescent 2D di-layer Janus-shaped film, derivative 3D Janus tube and 3D plus 2D complete flag-shaped structures are constructed.
Impact of dehydration and mechanical amorphization on the magnetic properties of Ni(ii)-MOF-74
Authors: Muratović Senada , Karadeniz Bahar , Stolar Tomislav , Lukin Stipe , Halasz Ivan , Herak Mirta , Mali Gregor , Krupskaya Yulia , Kataev Vladislav , Žilić Dijana , Užarević Krunoslav
Published: April 2020

While desolvation process does not influence the magnetism of Ni-MOF-74, amorphization causes partial nickel(ii) spin-crossover fromS= 1 toS= 0 and the decrease of the bulk magnetization.
Synergetic magnetic and luminescence switching via solid state phase transitions of the dysprosium–dianthracene complex
Authors: Liu Jing-Cui , Huang Xin-Da , Zou Qian , Bao Song-Song , Wang Xi-Zhang , Ma Jing-Yuan , Zheng Li-Min
Published: April 2020

A dinuclear complex Dy2L2(depma2)Cl2 containing a pre-photodimerized dianthracene phosphonate ligand (depma2) undergoes consecutive two-step structural transformation upon heating depma2, accompanied by a synergetic switching of the photoluminescence and magnetic dynamics.
In situ growth of Au–Ag bimetallic nanorings on optical fibers for enhanced plasmonic sensing
Authors: Shi Se , Li Anran , Huang Renliang , Yu Jing , Li Shuzhou , Qi Wei , He Zhimin , Su Rongxin
Published: April 2020

Au–Ag bimetallic nanorings were grown in situ on an optical fiber surface via bioinspired PDA, a synergetic GRR and metal deposition, which exhibited enhanced LSPR sensitivity and oxidation resistance.
Evidence for dimerization of ferroportin in a human hepatic cell line using proximity ligation assays
Authors: Rishi Gautam , Secondes Eriza S. , Wallace Daniel F. , Subramaniam V. Nathan
Published: April 2020

Mutations in the only known iron exporter ferroportin (FPN) in humans are associated with the autosomal dominantly inherited iron overload disorder ferroportin disease or type IV hereditary hemochromatosis (HH). While our knowledge of the central role of FPN in iron homeostasis has grown in the last 20 years, there exist some questions surrounding the structure and membrane topology of FPN with conflicting data on whether this receptor acts as a monomer or a multimer. To investigate and determine if FPN dimerization occurs in cells, we used novel tools including a variety of different FPN constructs expressing different tagged versions of the protein, a novel antibody that only detects cell surface FPN and proximity ligation assays. The results of the present study suggest that both the carboxy- and amino-termini of the FPN protein are intracellular. We also show that exogenously transfected FPN forms dimers; these dimers can be formed between the wild-type and mutant FPN proteins. This is the first study to examine the intracellular dimerization of FPN protein. Using proximity ligation assays, we show intracellular localization of FPN dimers and the interaction between FPN and hepcidin proteins as well. These results have important implications in the field of iron metabolism and add to our knowledge about FPN membrane topology and physiology of iron transport. This will be of importance in understanding the clinical implications of FPN mutations and of interest to future research aimed at targeting FPN expression to modulate iron homeostasis.
The road to the structure of the mitochondrial respiratory chain supercomplex
Authors: Caruana Nikeisha J. , Stroud David A.
Published: April 2020

The four complexes of the mitochondrial respiratory chain are critical for ATP production in most eukaryotic cells. Structural characterisation of these complexes has been critical for understanding the mechanisms underpinning their function. The three proton-pumping complexes, Complexes I, III and IV associate to form stable supercomplexes or respirasomes, the most abundant form containing 80 subunits in mammals. Multiple functions have been proposed for the supercomplexes, including enhancing the diffusion of electron carriers, providing stability for the complexes and protection against reactive oxygen species. Although high-resolution structures for Complexes III and IV were determined by X-ray crystallography in the 1990s, the size of Complex I and the supercomplexes necessitated advances in sample preparation and the development of cryo-electron microscopy techniques. We now enjoy structures for these beautiful complexes isolated from multiple organisms and in multiple states and together they provide important insights into respiratory chain function and the role of the supercomplex. While we as non-structural biologists use these structures for interpreting our own functional data, we need to remind ourselves that they stand on the shoulders of a large body of previous structural studies, many of which are still appropriate for use in understanding our results. In this mini-review, we discuss the history of respiratory chain structural biology studies leading to the structures of the mammalian supercomplexes and beyond.
Profiles of Early Actions and Gestures in Infants With an Older Sibling With Autism Spectrum Disorder
Authors: West Kelsey L. , Roemer Emily J. , Northrup Jessie B. , Iverson Jana M.
Published: April 2020

Purpose

Infants with autism spectrum disorder (ASD) produce fewer play actions and gestures than neurotypical infants (e.g., Mastrogiuseppe et al., 2015; Veness et al., 2012; Zwaigenbaum et al., 2005). The purpose of this study was to investigate whether different “types” of actions and gestures are more or less likely to develop atypically in ASD.

Method

We examined eight types of actions and gestures longitudinally from ages 8 to 14 months in 80 infants with a heightened risk for developing ASD by virtue of having an affected older sibling (high risk [HR]; e.g., Ozonoff et al., 2011) and 25 infants with no such familial risk (low risk). Data were collected using the MacArthur–Bates Communicative Development Inventories (Fenson et al., 1994, 1993).

Results

HR infants later diagnosed with ASD showed less growth across nearly all types of actions and gestures compared to the low-risk comparison group. Importantly, these HR infants who were later diagnosed with ASD also exhibited reduced growth in frequent deictic gestures and in actions that involve object manipulation relative to HR infants with non-ASD language delay.

Conclusions

During infancy, it is challenging for clinicians to distinguish ASD from other early communicative delays (e.g., Camarata, 2014). Our results indicate that deictic gestures, as well as actions and gestures involving object manipulation, may be useful targets of surveillance strategies for HR infants and could support early detection efforts for ASD.
Bayesian multilevel random‐effects model for estimating noise in image sensors
Authors: Riutort‐Mayol Gabriel , Gómez‐Rubio Virgilio , Marqués‐Mateu Ángel , Lerma José Luis , López‐Quílez Antonio
Published: April 2020

Sensor noise sources cause differences in the signal recorded across pixels in a single image and across multiple images. This study presents a Bayesian approach to decomposing and characterising the sensor noise sources involved in imaging with digital cameras. A Bayesian probabilistic model based on the (theoretical) model for noise sources in image sensing is fitted to a set of a time‐series of images with different reflectance and wavelengths under controlled lighting conditions. The image sensing model is a complex model, with several interacting components dependent on reflectance and wavelength. The properties of the Bayesian approach of defining conditional dependencies among parameters in a fully probabilistic model, propagating all sources of uncertainty in inference, makes the Bayesian modelling framework more attractive and powerful than classical methods for approaching the image sensing model. A feasible correspondence of noise parameters to their expected theoretical behaviours and well‐calibrated posterior predictive distributions with a small root mean square error for model predictions have been achieved in this study, thus showing that the proposed model accurately approximates the image sensing model. The Bayesian approach could be extended to formulate further components aimed at identifying even more specific parameters of the imaging process.
Symbol positions‐based Slepian–Wolf coding with application to distributed video coding
Authors: Benierbah Said , Khamadja Mohammed
Published: April 2020

In this study, the authors will show that coding the positions of the symbols, instead of their values, can be a good way to implement efficient Slepian–Wolf (SW) coding and can reduce the complexity of both the encoder and the decoder. The authors will also propose a practical distributed video coding (DVC) system that exploits this idea. This system will use binary maps to indicate the positions of the most probable symbols, instead of separating them into bitplanes. Simulations show that this position‐based SW coding allows a simple and more efficient DVC system with improved rate‐distortion performance, compared to the bitplane‐based DVC system that uses the same side information. The memory requirements at the encoder are reduced by about 50% and the number of channel coding operations is also reduced. This DVC system also allows to use an easy way to control quantisation, reduces the decoding latency, and allows fast parallel decoding.
Approach to model human appearance based on sparse representation for human tracking in surveillance
Authors: Damotharasamy Sangeetha
Published: April 2020

In human tracking, sparse representation successfully localises the human in a video with minimal reconstruction error using target templates. However, the state‐of‐the‐art approaches use colour and local appearance of a human to discriminate the human from the background regions, and hence fail when the human is occluded and appears in the varying illumination environment. In this study, a robust tracking algorithm is proposed that utilises gradient orientation and fine and coarse sparse representation of the target template. Sparse representation‐based human appearance model utilises weighted gradient orientation that is insensitive to illumination variation. Coarse and fine representation of sparse code facilitates tracking under varying scales. Subspace learning from image gradient orientation is enforced with occlusion detection during the dictionary updation stage to capture the visual characteristics of the local human appearance that supports tracking under partial occlusion with lesser tracking error. The proposed human tracking algorithm is evaluated on various datasets and shows efficient human tracking performance when compared to the other state‐of‐the‐art approaches. Furthermore, the proposed human tracking algorithm is suitable for surveillance applications.
Accurate leukocoria predictor based on deep VGG‐net CNN technique
Authors: Subrahmanyeswara Rao Boyina
Published: April 2020

The most important part of digital image analysis is object classification. Nowadays, deep learning makes an enormous achievement in computer vision problems. So there has been a lot of interests in applying features learned by convolutional neural networks (CNNs) on general image recognition to more tasks such as object detection, segmentation and face recognition. Leukocoria detection is one of the serious challenges in infant retinal treatment. Leukocoria is represented as an abnormal white reflection appearing in the eyes of an infant suffering from retinoblastoma. This research proposes a deep Visual Geometry Group‐net CNN classifier for automatic detection of leukocoria. The proposed classifier comprises pre‐processing, feature extraction and classification. The deep CNN classifier contains convolution layer, pooling layer and fully connected layer with weights are developed on each image. Experimental results based on several eye images consist of ordinary and leukocoric from flicker, and it demonstrates that the proposed classifier provides better results with the accuracy of 98.5% and the error rate is below 2% which exceeds the current results.
Empirical greedy machine‐based automatic liver segmentation in CT images
Authors: Mourya Gajendra Kumar , Bhatia Dinesh , Handique Akash
Published: April 2020

Segmentation of the liver from 3D computed tomography volumes plays a significant role in trajectory development for computer‐assisted interventional surgery for the liver disease. Despite a lot of studies, liver segmentation remains a challenging task due to the lack of clear edges on most liver boundaries coupled with high variability of both anatomical and intensity patterns. In addition, there is a problem with the segmentation of the left portal vein, in which the size of this vein prominently estimates the liver tumour area. The empirical greedy machine is proposed to make the precise, automated segmentation of the liver as well as the left portal vein. In which the empirical robust nature trains the features of the liver proficiently thereby segmenting the liver from other organs without the omission of adjacent organs and liver lobe region. Hence this proposed method can achieve one of the highest accuracies compared to other segmentation methods and the performance is calculated using several parameters such as volumetric overlap error, relative absolute volume difference (RVD), average symmetric absolute surface distance (ASD), root mean square surface distance, maximum symmetric ASD.
Comparative analysis of texture feature extraction techniques for rice grain classification
Authors: Robert Singh Kshetrimayum , Chaudhury Saurabh
Published: April 2020

Classifications of eight different varieties of rice grain are discussed in this study based on various texture models. Four local texture feature extraction techniques are proposed and three sets of texture features (SET‐A, SET‐B and SET‐C) are formed, for the classification task. Performances of the proposed feature sets are compared with the existing techniques based on, run length matrix, co‐occurrence matrix, size zone matrix, neighbourhood grey tone difference matrix and wavelet decomposition, towards classification of rice grain using a back propagation neural network (BPNN). The proposed techniques are also tested against publicly available data from Brodatz's texture data set and their results are compared with other techniques. The classification accuracy by the BPNN classifier is also compared with other statistical classifiers namely, K‐nearest neighbour, linear discriminant classifier and Naive Bayes classifier. It is found that, the proposed feature sets yield better classification results on both rice data and Brodatz's data. Results show that, feature SET‐B, is able to classify rice grain with an average classification accuracy of 99.63% with a minimum of six features.
Multi‐head mutual‐attention CycleGAN for unpaired image‐to‐image translation
Authors: Ji Wei , Guo Jing , Li Yun
Published: April 2020

The image‐to‐image translation, i.e. from source image domain to target image domain, has made significant progress in recent years. The most popular method for unpaired image‐to‐image translation is CycleGAN. However, it always cannot accurately and rapidly learn the key features in target domains. So, the CycleGAN model learns slowly and the translation quality needs to be improved. In this study, a multi‐head mutual‐attention CycleGAN (MMA‐CycleGAN) model is proposed for unpaired image‐to‐image translation. In MMA‐CycleGAN, the cycle‐consistency loss and adversarial loss in CycleGAN are still used, but a mutual‐attention (MA) mechanism is introduced, which allows attention‐driven, long‐range dependency modelling between the two image domains. Moreover, to efficiently deal with the large image size, the MA is further improved to the multi‐head mutual‐attention (MMA) mechanism. On the other hand, domain labels are adopted to simplify the MMA‐CycleGAN architecture, so only one generator is required to perform bidirectional translation tasks. Experiments on multiple datasets demonstrate MMA‐CycleGAN is able to learn rapidly and obtain photo‐realistic images in a shorter time than CycleGAN.
Losses do not prevent wide band metamaterial true time delay line applications, GaAs MMIC experimental verification
Authors: Herbette Quentin , Géron Emmanuel , Dichi Thierry , Pillet Grégoire , Lucas Jerome
Published: April 2020

Losses are often the impairing feature of metamaterial true time delay line devices. In this study, the authors analytically demonstrate that ohmics losses in this kind of structures as well as impedance mismatch depend on the bandwidth. These results allow to consider wide band application for radar systems. It is verified experimentally that metamaterial delay line devices are fitted for wide band delay line applications for they allow low insertion losses, low return loss and tunable delay.
Compact dual‐band near/far‐field dipole antenna/tag
Authors: Jafargholi Amir , Salehi Mostafa , Bagheri Alireza
Published: April 2020

This study presents a compact printed dipole antenna/tag loaded by metamaterial (MTM) inclusions for portable near/far‐field communication/identification applications. It is shown that loading a printed dipole antenna by epsilon negative inclusions can lead to achieving the miniaturised, dual‐band, low‐profile antenna. To realise this concept, inductively loaded wire (ILW) has been proposed. To implement inductive loads a meander‐line structure is designed and manufactured. Simulation results show that placing the MTM cell in the vicinity of a dipole antenna causes to having an additional resonant frequency which is lower than the natural resonant frequency of a simple unloaded dipole antenna. With the aid of ILW‐MTM, a low‐frequency band at 2400 MHz for the wireless local area network (WLAN) and near‐field radio frequency identification applications is achieved. The higher frequency band is expanded for 5800 MHz services (4900–6500 MHz) WLAN and worldwide interoperability for microwave access band. The antenna prototype is fabricated and measured. Good agreement has been observed between the simulation and measurement results.
Compact and wideband filtenna for circularly polarised application
Authors: Wang Wenlei , Luo Guo Qing , Jin Huayan , Fan Kuikui , Hao Zhang Chen
Published: April 2020

A compact single M‐shaped probe fed circularly polarised filtenna (filtering antenna) without extra filtering circuit is presented in this study, in which three pair slots with different lengths are etched on its parasitic patch to produce radiation nulls at both band edges of its operating band. Furthermore, a single M‐shaped probe feeding structure is used to improve the selectivity, especially for the lower band edge. By merging the filtering circuit into a radiating element, a good selectivity in the gain response can be realised without influencing the operation band aperture efficiency. A sample is fabricated and results show that the proposed filtenna has an operating bandwidth of 13% (|S11| < −10 dB, AR < 3 dB) with a centre frequency of 5 GHz, a peak gain of 8.9 dBic, and an average gain of 8.3 dBic within its operating bandwidth. Radiation nulls at 3.93, 5.97 and 6.36 GHz introduced by the three pairs of slots have been successfully generated. The radiation patterns are stable within the whole wide operating band.
TEM‐TE11 mode converter antenna like a pelican beak
Authors: Hosseini Seyed Jalil , Oraizi Homayoon
Published: April 2020

In this study, a design, simulation, fabrication, and measurement of the TEM‐TE11 mode converter antenna (MCA) like a pelican beak are investigated. The working frequency of the pelican beak‐shaped MCA (PBMCA) is the frequency in the range of 3.9–4.6 GHz (700 MHz bandwidth). Due to increasing the antenna cross‐section, the probability of the electrical breakdown dramatically reduces. Electrical breakdown may occur at very high power outputs of the electromagnetic sources. The power‐handling capacity of the PBMCA is 829 MW, at the centre frequency. The antenna is simulated and measured at three frequencies. The simulation results are a good agreement with the measurement results.
Scaling relations and baryonic cycling in local star-forming galaxies
Authors: Ginolfi M. , Hunt L. K. , Tortora C. , Schneider R. , Cresci G.
Published: April 2020

Metallicity and gas content are intimately related in the baryonic exchange cycle of galaxies, and galaxy evolution scenarios can be constrained by quantifying this relation. To this end, we have compiled a sample of ∼400 galaxies in the local Universe, dubbed “MAGMA” (Metallicity And Gas for Mass Assembly), which covers an unprecedented range in parameter space, spanning more than 5 orders of magnitude in stellar mass (Mstar), star-formation rate (SFR), and gas mass (Mgas), and it has a factor of ∼60 in metallicity [Z, 12 + log(O/H)]. Stellar masses and SFRs were recalculated for all of the galaxies using IRAC, WISE, and GALEX photometry, and 12 + log(O/H) was transformed, where necessary, to a common metallicity calibration. To assess the true dimensionality of the data, we applied multidimensional principal component analyses (PCAs) to our sample. We find that even with the vast parameter space covered by MAGMA, the relations between Mstar, SFR, Z, and Mgas (MHI + MH2) require only two dimensions to describe the hypersurface, which confirms the findings of previous work. To accommodate the curvature in the Mstar–Z relation, we applied a piecewise 3D PCA that successfully predicts observed 12 + log(O/H) to an accuracy of ∼0.1 dex. MAGMA is a representative sample of isolated star-forming galaxies in the local Universe, and it can be used as a benchmark for cosmological simulations and to calibrate evolutionary trends with redshift.
Atmospheric stability and collapse on tidally locked rocky planets
Authors: Auclair-Desrotour P. , Heng K.
Published: April 2020

Context.Over large timescales, a terrestrial planet may be driven towards spin-orbit synchronous rotation by tidal forces. In this particular configuration, the planet exhibits permanent dayside and nightside, which may induce strong day-night temperature gradients. The nightside temperature depends on the efficiency of the day-night heat redistribution and determines the stability of the atmosphere against collapse.

Aims.To better constrain the atmospheric stability, climate, and surface conditions of rocky planets located in the habitable zone of their host star, it is thus crucial to understand the complex mechanism of heat redistribution.

Methods.Building on early works and assuming dry thermodynamics, we developed a hierarchy of analytic models taking into account the coupling between radiative transfer, dayside convection, and large-scale atmospheric circulation in the case of slowly rotating planets. There are two types of these models: a zero-dimensional two-layer approach and a two-column radiative-convective-subsiding-upwelling model. They yield analytical solutions and scaling laws characterising the dependence of the collapse pressure on physical features, which are compared to the results obtained by early works using 3D global climate models (GCMs).

Results.The analytical theory captures (i) the dependence of temperatures on atmospheric opacities and scattering in the shortwave and in the longwave, (ii) the behaviour of the collapse pressure observed in GCM simulations at low stellar fluxes that are due to the non-linear dependence of the atmospheric opacity on the longwave optical depth at the planet’s surface, (iii) the increase of stability generated by dayside sensible heating, and (iv) the decrease of stability induced by the increase of the planet size.
A distinct magnetic property of the inner penumbral boundary
Authors: Jurčák Jan , Schmassmann Markus , Rempel Matthias , Bello González Nazaret , Schlichenmaier Rolf
Published: April 2020

Context. Analyses of sunspot observations revealed a fundamental magnetic property of the umbral boundary: the invariance of the vertical component of the magnetic field.

Aims. We analyse the magnetic properties of the umbra-penumbra boundary in simulated sunspots and thus assess their similarity to observed sunspots. We also aim to investigate the role of the plasma β and the ratio of kinetic to magnetic energy in simulated sunspots in the convective motions because these quantities cannot be reliably determined from observations.

Methods. We used a set of non-gray simulation runs of sunspots with the MURaM code. The setups differed in terms of subsurface magnetic field structure and magnetic field boundary imposed at the top of the simulation domain. These data were used to synthesize the Stokes profiles, which were then degraded to the Hinode spectropolarimeter-like observations. Then, the data were treated like real Hinode observations of a sunspot, and magnetic properties at the umbral boundaries were determined.

Results. Simulations with potential field extrapolation produce a realistic magnetic field configuration on the umbral boundaries of the sunspots. Two simulations with a potential field upper boundary, but different subsurface magnetic field structures, differ significantly in the extent of their penumbrae. Increasing the penumbra width by forcing more horizontal magnetic fields at the upper boundary results in magnetic properties that are not consistent with observations. This implies that the size of the penumbra is given by the subsurface structure of the magnetic field, that is, by the depth and inclination of the magnetopause, which is shaped by the expansion of the sunspot flux rope with height. None of the sunspot simulations is consistent with the observed properties of the magnetic field and the direction of the Evershed flow at the same time. Strong outward-directed Evershed flows are only found in setups with an artificially enhanced horizontal component of the magnetic field at the top boundary that are not consistent with the observed magnetic field properties at the umbra-penumbra boundary. We stress that the photospheric boundary of simulated sunspots is defined by a magnetic field strength of equipartition field value.
Energy scaling laws for geometrically linear elasticity models for microstructures in shape memory alloys
Authors: Conti Sergio , Diermeier Johannes , Melching David , Zwicknagl Barbara
Published: April 2020

We consider a singularly-perturbed two-well problem in the context of planar geometrically linear elasticity to model a rectangular martensitic nucleus in an austenitic matrix. We derive the scaling regimes for the minimal energy in terms of the problem parameters, which represent the shape of the nucleus, the quotient of the elastic moduli of the two phases, the surface energy constant, and the volume fraction of the two martensitic variants. We identify several different scaling regimes, which are distinguished either by the exponents in the parameters, or by logarithmic corrections, for which we have matching upper and lower bounds.
Microclimatological conditions at the Imingfjell mountain, Norway: comparison of model results with observed data
Authors: Vasiakina Anastasiia , Renssen Hans , Aartsma Peter , Kurovskaia Viktoriia
Published: April 2020

Models are often used when data is insufficient. However, it is difficult to assess how well they perform, especially for mountainous areas. The Community Land Model 4.5 was selected for testing with the Imingfjell mountain in Norway as a research area. Weather parameters from two nearest meteorological stations and energy fluxes for lichens and shrubs on the Imingfjell were used for comparison with model input and output data, respectively. Calculated by the model temperature from the input was higher by 1-2 °C than from the stations meaning the model underestimates the Imingfjell elevation by 3 times, possibly due to its spatial resolution. As for output data comparison, mean values for modelled soil heat fluxes slightly differed from field data by only 1-3 W/m2. However, these similarities cannot be considered significant due to average correlation coefficients (0.63 for model/lichen and 0.51 – model/shrub).
Causes and consequences of the streambed restructuring of the Koiavgan Creek (North Caucasus, Russia)
Authors: Kharchenko Sergey , Tsyplenkov Anatoly , Petrakov Dmitry , Golosov Valentin
Published: April 2020

The restructuring of the lower reach of the Koiavgan Creek channel (the right bank tributary of the Djankuat River) occurred on 1 July 2015 after continuous rainfall with a total precipitation amount of 227 mm. This led to the breakthrough of the Djankuat Glacier lateral moraine. The lower reach of the creek channel was initially formed at the junction of the bedrock slopes and lateral moraine and descended sharply at the end of the moraine to a wide glacial valley of the Djankuat River. The part of the channel from the end of the moraine line to the creek’s outlet in the bottom of the glacial valley had a height difference of 125 m at a distance of about 250 m. The active landslide has been recorded in the place of future breakthrough based on interpretation of 2014 summer satellite image. The linear erosion began to form on the wall of the disruption. Thermokarst processes probably also contributed to this breakthrough. The total volume of sediment eroded during the breakthrough and for four years after is 156 500 m3. The breakthrough has formed the largest sediment cone 300 meters wide and more than 200 m long in the bottom of the Djankuat River valley.
Flash floods: formation, study and distribution
Authors: Kuksina Liudmila , Golosov Valentin
Published: April 2020

Flash floods are one of the most widespread and dangerous phenomenon on our planet. They are characterized by fast speed of development and short duration. However their study just begins because there is no one opinion what flash flood is, and there is no special term in many countries. The key reasons of their formation are intensive rainfall of short duration, location of river basin in mountain areas, and small catchment area, providing fast concentration of the runoff in river channel. Another significant factor is antecedent soil moisture. Flash floods are mostly spread in zones of subtropic, tropic and equatorial climate in the northern hemisphere. The study of flash floods is implemented in various fields of science due to hydrometeorological and lythogeomorphological causes of their formation. The important task is the differentiation of flash floods and debris flows. It can be based on the relations between sediment yield and sediments grain size and runoff characteristics with a glance of sediments concentration. The scheme of natural factors of flash floods formation is suggested with their differentiation from debris flows and floods of other types. The main issues of flash floods research and forecast are connected with small spatio-temporal scale of phenomenon and remoteness of river basins.
Detecting and Searching for subglacial lakes through airborne radio-echo sounding in Princess Elizabeth Land (PEL), Antarctica
Authors: Cui Xiangbin , Lang Shinan , Guo Jingxue , Sun Bo
Published: April 2020

Over 400 subglacial lakes were discovered in Antarctica through radio-echo sounding (RES) method and remote sensing. Subglacial lakes have significance in lubricating ice-bedrock interface and enhancing ice flow. Moreover, ancient lives may exist in the extreme environment. Since 2015, the “Snow Eagle 601” BT-67 airborne platform has been deployed and applied to map ice sheet and bedrock of Princess Elizabeth Land. One of great motivations of airborne surveys is to detect and search for subglacial lakes in the region. In this paper, we provided preliminary results of RES over both old and new discovered lakes, including Lake Vostok, a potential second large subglacial lake and other lakes beneath interior of the ice sheet in Antarctica.
Water tracks in the lower Lena River basin
Authors: Tarbeeva Anna , Lebedeva Lyudmila , Efremov Vladimir , Shamov Vladimir , Makarieva Olga
Published: April 2020

In the permafrost regions, where water filtration zone is limited by the shallow active layer, the surface flow forms a network of hollows, called «water tracks», oriented along the slope gradient. Water tracks are clearly distinguished on satellite images, but poorly defined in the field. The pattern of the water tracks network depends on geomorphological position, permafrost and geological conditions and dominant cryogenic processes. Surface flow could occur in the water tracks during the snowmelt and heavy rains, when the soil is entirely frozen or fully saturated by water. In dry periods, the water tracks form retention zones due to low filtration rates and significant capacity of thawed soil beneath the troughs. Our study of water tracks in the north-western Yakutia showed the changes of their morphology from upstream towards downstream. The water levels in the water tracks have a pronounced diurnal course in reverse phase to the water temperature variation. They are related to diurnal ground thawing dynamics. Hydrology of water tracks depends on the peat thickness, active layer properties and lithology. Water tracks formed by rubble rocks respond to a storm event with rapidly increasing water level. The deeper thawing layer, the smoother water levels rise and decrease.
Ice-covering hydrological and hydrochemical investigations on the Lena River delta
Authors: Fedorova Irina , Zdorovennov Roman , Zdorovennova Galina , Aksenov Aleksei
Published: April 2020

The study reported here was conducted on the channels of the Lena River delta in April 2019. The water temperature, specific conductivity, dissolved oxygen, PAR fluxes, and currents were measured on the cross-sections in the Olenekskaya and Bykovskaya channels, as well as in the main channel of the Lena River near Samoilov Island using the multiparameter probes CTD-48M, CTD-90M and RBR-Concerto. An analysis of the data showed that the water in the channels of the Lena River delta in winter is well saturated with oxygen (4.9-6.3 ml/l), has a very low temperature (from -0.1°C to +0.8°C). The specific conductivity of water Lena River delta channels changed from 460 to 530 )S/cm. A thick layer of snow 0.1-0.5 m with an ice thickness of more than 1.5 m prevents the penetration of solar radiation into the subglacial layer, where the PAR fluxes does not exceed 10 µmol/m2s. Current velocities reached 20–25 cm/s in the Bykovskaya channel, in Olenekskaya channel – 5-11 cm/s, and in the main channel – 12-18 cm/s. The currents data obtained made it possible to calculate the discharge in the channels during the ice-period.
Web GIS for analysis of the past and future of the climate and hydrological conditions in the North-West of Russia
Authors: Kazakov Eduard , Zhuravlev Sergey , Kurochkina Lyubov , Ayzel Georgy
Published: April 2020

This paper discusses the development of a specialized web GIS (geoportal) dedicated to the analysis of changes in climate conditions and hydrological regime in the North-West of Russia. One of the main goals of geoportal is to provide a tool to answer simple questions about climate for wide range of users. For example, how has the climate and hydrology changed in a particular city over the past 70 years? What will it be like in 50 years? The main functionality, data and creation technologies are presented. Geoportal offers the tools that allow interactive processing of daily data time series on minimum, average, maximum air temperatures, precipitation and surface runoff, represented by both reanalysis data from 1950 and predictive data up to 2100. Information about actual observations at weather stations and hydrological posts is also available. Access to the geoportal is provided through the user’s web GIS interface and through the HTTP interface for developers, which opens up opportunities for integrating data into third-party services.
Water bodies of Altai Krai (Russia): the condition analysis and quality improvement opportunities
Authors: Korovina Oksana , Somin Vladimir , Komarova Larisa
Published: April 2020

The characteristics of surface and groundwater of the Altai Territory (Russia) are considered, the possibility of using groundwater of various horizons for domestic use is evaluated. The pollution of water bodies by compounds of heavy metals and oil products is analyzed.
The main characteristics of slope and river runoff transformations under the conditions of degradation of natural complexes on the catchment
Authors: Gareev Aufar , Gainanshin Mansur
Published: April 2020

The article shows that conducting hydrological calculations in the basins of very small and small rivers and their catchments is associated with significant errors, which is accounted for not only by the drastic limitations of the observational materials, but is also due to significant slope and river runoff transformations depending on the impact of natural complexes degradation (plant communities, soil cover, etc.). In the meantime, it should be noted that the emergence of a number of adverse processes, such as the propagation of erosion and channel processes, floods, environmental and economic damage inflicted on natural and economic systems, etc. is largely associated with the slope and river runoff transformations. This predetermines the necessity of investigating the processes in question. Given the above-mentioned, the article serves to reflect the results of research conducted within the mountain forest area of the Southern Urals and the Cis-Urals by the academic staff of the Department of hydrometeorology and geoecology of the Bashkir state university from 1955 to 2012. The main factors contributing to the increased maximum water discharge during the spring flood are confined to an increase in the modules of runoff coefficients as the scale of anthropogenic load on natural complexes increases, and, consequently, to a decrease in the natural water-regulating capacity of the catchments. The above-mentioned processes have resulted in the increasing maximum values of slope and river runoff and account for the adverse effects observed in the natural, economic and ecological systems.
Dependence between infiltration capacity and karst processes in river catchments
Authors: Iofin Zinoviy
Published: April 2020

The article shows the empirical dependence between the cavern volume filled with water and infiltration capacity. This dependence makes it possible to estimate how karst influences infiltration capacity and run-off and water balance as well.
Identification of matter flows in marginal filters of rivers (based on the principles of thermodynamics)
Authors: Khaustov Aleksandr , Redina Margarita , Nemirovskaya Inna
Published: April 2020

Material and energy flows in the marginal filters of rivers identified based on the analyses of the environmental fate of polycyclic aromatic hydrocarbons (PAH): Anthracene (An), Phenanthrene (Phen), Naphthalene (Naph), Pyrene (Py), Fluoranthene (Flu), Chrysene (Chr), Benzo[a]pyrene (BaP), Perylene (Pl). Experimental data on the components of the aquatic system of the marginal filter of the Northern Dvina River allow us to consider the processes of phase transitions of PAHs at geochemical barriers (GCB). Based on the principles of thermodynamics, a phenomenological model of migration and the formation of the most persistent PAH associations on the barriers is formed. The predominant possibility of PAH migration on suspended material, including biota, is shown. The probability of PAH accumulation between the most important components of aquatic systems was assessed according to the conditions of their migration activity in various zones of the marginal filter. Active and passive PAHs were determined in terms of their migration and accumulation in the components of aquatic systems. The role of PAHs as a reliable indicator of thermodynamic processes, including the development of technogenesis, is estimated.
Channel processes of a small river heavily modified by human activities
Authors: Varenov Aleksandr , Tarbeeva Anna , Botavin Dmitriy , Mikhaylova Nadezhda , Turykin Leonid , Chalova Aleksandra
Published: April 2020

Widely-spread small rivers are very poorly studied in relation to channel processes. The influence of local factors, high sensitivity to human impact, close connection with basin processes, and relatively low rates of channel changes distinguish them from medium and large ones and make it necessary to form a special approach to studies. Based on collection of long-term maps and local residents’ interviews, we reconstructed the transformation of channels in the Kudma River basin (the Volga Upland) for the last 200 years. Based on the bank erosion monitoring during 2011-2019 the modern rates of channel changes were revealed. We found that significant human impact is associated with the artificial channels cutoffs and draining of ponds which led to channel incision of the Kudma and Ozerka Rivers in the middle reaches and the transformation of floodplain into terrace. Agriculture development caused siltation of the upper reaches of rivers. The rivers of the forested part of the basin experienced the least human changes. From 2011 to 2019 the maximum rates of bank erosion were found to be within range of 0.3 to 2.7 m/year and supposed to be driven by peak water discharge.
Magnetic studies of monoclinic Cu4O(SeO3)3, a copper-oxo-selenite derivative
Authors: Malta José F. , Henriques Marta S.C. , Paixão José A. , Gonçalves António P.
Published: April 2020

Cu4O(SeO3)3 is a copper-oxo-selenite belonging to the CuxO(SeO3)(x–1) family of the topological chiral magnet Cu2OSeO3. We report magnetometry and specific heat data measured in a monoclinic Cu4O(SeO3)3 single crystal grown through a Chemical Vapour Transport (CVT) reaction. Our study shows a typical antiferromagnetic behaviour, with a Néel temperature TN = 58 K, similar to that of the Cu2OSeO3 and an additional transition at 13 K. The effective magnetic moment per Cu atom is 1.84 μB, close to the expected theoretical value for Cu2+. The low-temperature M(H) curves, show a transition starting at Hc1 ~ 400 Oe at 1.8 K shifting to a lower value of ~ 280 Oe at 30 K, likely from a helical into a conical intermediate phase, and a second transition at Hc2 ~ 1 kOe, above which the net moment increases linearly with applied field. The magnetisation moment value in a 90 kOe field is 0.053 μB/Cu at 1.8 K and attains a maximum value of 0.061 μB at 13 K. Low-temperature specific heat measurements confirm the presence of the magnetic transition at 13 K, slightly shifting to lower temperatures under an applied magnetic field.