bluuebunny/crossref_metadata_2025 huggingface dataset:
Robust temporal low‐rank representation for traffic data recovery via fused lasso
Authors: Mao Ruyong , Chen Zhengyu , Hu Guobing
Published: January 2021

Achieving complete and accurate traffic data as input is crucial for most intelligent transportation systems. However, due to hardware or software malfunction, traffic data is inevitably faced with missing and noise problems. Most of the existing representation‐based traffic data recovery methods adopt sparse representation theory, which well models the local association properties of traffic data, but ignores their global correlation. To overcome this shortcoming, a robust low‐rank representation method that incorporates temporal prior information to impute the missing traffic data is proposed. Specifically, the low‐rank representation theory is first employed to model the global spatial correlation of traffic data, and then the fused lasso regularisation is utilized to fit the temporal correlation of traffic data. In addition, to make the proposed model more robust, F‐norm regularisation is used to smooth the Gaussian noise of traffic data. Furthermore, an efficient optimisation algorithm based on ADMM is developed to solve the proposed model. Finally, the extensive experiments performed on real dataset validate the effectiveness of the proposed method.
An approximate approach to estimation of dissociation rate of gas hydrate in porous rock bed
Authors: Dreus Andrii , Gubin Oleksandr , Bondarenko Volodymyr , Lysenko Roman , Liu Baochang
Published: January 2021

Development of deep shelf or onshore gas hydrate fields involves drilling wells with subsequent thermal, decompression or chemical action on the bed. In this case, the radius of thermal or decompression action is limited. As the field develops, recovery efficiency decreases, and necessity arises for drilling a new well that influences the cost of the technology. To determine the rational wells location, it is necessary to predict the advance of the phase transformation rate front into the depth of the bed. In this work, to study the movement dynamics of the gas hydrates dissociation front in a porous layer of rock, the Stefan problem solution is used. The method adequacy is substantiated by comparing the calculated results with known experimental data. The temperature fields are modelled in a porous bed during the methane hydrate dissociation. The temperature field dynamics for 200 days in a porous bed during the methane hydrate dissociation caused by thermal action is shown. The influence of porosity and excess temperature on the dissociation front movement rate is revealed.
Method for determining the starting moment of hydrate formation on the basis of optical effects
Authors: Pedchenko Nazar , Vynnykov Yuriy , Pedchenko Larysa , Pedchenko Mykhailo
Published: January 2021

The problem is analyzed of hydrate formation in the systems of gathering and treating of oil and gas products. The methods are studied for prevention of complications associated with the gas hydrates accumulation in the pipelines and process lines. Attention is focused on the significant material costs to prevent the hydrate formation and ways to reduce them. The necessity of constant laboratory monitoring for reservoir systems at industrial facilities to determine the hydrate formation parameters has been substantiated. The need to improve the method for determining the hydrate formation parameters for complex reservoir systems based on a mixture of hydrate-forming gases has also been proved. The purpose of the work is to improve the research method of reservoir systems immediately at the facilities of products mining and treatment. The peculiarities are analyzed of the method of visual laboratory observation in the study of gas hydrates. During experimental studies, optical effects of image distortion are observed due to the formation of a gas hydrate layer in the form of a film on the interphase surface. The mechanism of their formation, as well as the processes determining them have been substantiated. Based on this effect, a method of fixing the hydrate formation initial stage (beginning of crystal growth – mass crystallization) is proposed. For increasing the informative ability of the obtained images of hydrate formation processes, it is proposed to “paint” them with the help of colored light sources, as well as to regulate the intensity and direction of illumination. A number of photos are presented, which clearly illustrate the processes described in the paper.
Mud-volcanic deposits of methane gas hydrates in the Black Sea
Authors: Shnyukov Yevgeny , Kobolev Volodymyr , Yanko Valentina
Published: January 2021

This paper discusses the formation of a special mud-volcanic type of gas hydrate accumulation in the deep-water part of the Black Sea. The main conclusions are based on the results of geological and geophysical studies of mud volcanoes carried out in the course of numerous scientific cruises between 1970-2015. Comparison of the Black Sea submarine mud volcanoes with their on-land analogues indicates the possible use of compensatory depressions, called “recessed synclines”, accompanying mud volcanoes, which is revealed in the course of prospecting and exploration of mineral deposits. In the sea they are represented by ring deposits of methane gas hydrates.
Mining of methane from deposits subaquatic gas hydrates using OTEС
Authors: Klymenko Vasyl , Denysov Yuriy , Skrypnyk Oleksandr , Kononchuk Skrypnyk , Teliuta Ruslan
Published: January 2021

The article proposes to using Ocean Thermal Energy Conversion (OTEC) to increase the energy efficiency mining of methane from deposits subaquatic gas hydrates on the gas hydrate cycle (GHET), that will allow not to spend 10-15% of the extracted methane for power supply of a gas-producing complex (GPC). The circuit-technological solution GPC is described, according to which carbon dioxide is introduced into the gas hydrate layer to extract methane from gas hydrates. To improve the kinetics of the process of replacement of methane with carbon dioxide in gas hydrates, it is proposed do recirculation part of CO2. The scheme and cycle of gas-hydrate energy-technological installation GHET are given, which operates using OTEC and generates together with electricity for GPC, fresh water and cold. Based on the method proposed in this paper, a comparative thermodynamic analysis of installations using OTEC for Black Sea conditions was performed. by GHET and Anderson cycles and it is shown that the specific useful work obtained in the GHET cycle, approximately 3 times more, and energetic efficiency 1.5 times more.
Investigation of the efficiency of gas condensate reservoirs waterflooding at different stages of development
Authors: Burachok Oleksandr , Kondrat Oleksandr , Matkivskyi Serhii
Published: January 2021

The study of flooding gas condensate reservoirs at different stages of depletion (25, 50, 75% of the dew point pressure and at the maximum condensation pressure) with different potential hydrocarbon content of 100, 300 and 500 g/m3 and different voidage replacement by using injection (50, 100 and 150%). The results showed a positive effect of water injection on the increase of the condensate recovery factor, but a decrease in gas production compared to the basic options of development at depletion drive. Thus, for formation systems with medium and high potential yield of liquid hydrocarbons C5+, the largest incremental production is obtained in the case when water injection begins with minimum depletion of formation energy. While for a formation system with a low potential yield (100 g/m3) the maximum technological effect is obtained under the condition of maximum depletion. In the case of medium and high C5+ yield in the formation gas, with a slight decrease in the formation pressure by 25 or 50% of the dew point pressure, the maximum increase in the condensate recovery factor is achieved at high injection rates with 100 or 150% voidage replacement. The obtained results can be used for rapid screening of potential methods of impact on the gas condensate reservoir, and the final decision concerning the technological parameters of production and injection wells operation will be made due to the results of optimization of multivariate hydrodynamic calculations using geological and technological models.
Geothermal heat use to eliminate hydrate formations in oil deposit injection wells
Authors: Fyk Мykhailo , Biletskyi Volodymyr , Аbbood Madjid , Аnzian Fabris
Published: January 2021

The article is devoted to an actual issue: the development of internal downhole heat exchangers technology to combat hydration in injection wells. Purpose: development of conceptual solutions for the use of geothermal coolant in the internal well heat exchanger of the injection well. A scheme of an internal downhole heat exchanger with a geothermal heat carrier has been developed, and includes a supply line of a geothermal carrier through the heat exchange surface of the injection well into the productive reservoir of the oil field. The scheme provides targeted utilization of thermobaric energy of a geothermal source to combat hydration in the injection well. A mathematical apparatus for describing the process of heat utilization and heat exchange in injection well is proposed. It is established that the capacity of one geothermal well discovered at the oil depths in the Dnipro-Donetsk basin is sufficient to eliminate hydration in 1-3 injection wells, and determines the feasibility of their joint work.
Effects of Normobaric Hypoxia on Matched-severe Exercise and Power-duration Relationship
Authors: Sousa Ana Catarina , Millet Gregoire P. , Viana João , Milheiro Jaime , Reis Vítor
Published: January 2021

We investigated the effects of hypoxia on matched-severe intensity exercise and on the parameters of the power-duration relationship. Fifteen trained subjects performed in both normoxia and normobaric hypoxia (FiO2=0.13, ~3000 m) a maximal incremental test, a 3 min all-out test (3AOT) and a transition from rest to an exercise performed to exhaustion (Tlim) at the same relative intensity (80%∆). Respiratory and pulmonary gas-exchange variables were continuously measured (K5, Cosmed, Italy). Tlim test’s V̇O2 kinetics was calculated using a two-component exponential model. V̇O2max (44.1±5.1 vs. 58.7±6.4 ml.kg-1.min-1, p<0.001) was decreased in hypoxia. In Tlim, time-to-exhaustion sustained was similar (454±130 vs. 484±169 s) despite that V̇O2 kinetics was slower (τ1: 31.1±5.8 vs. 21.6±4.7 s, p<0.001) and the amplitude of the V̇O2 slow component lower (12.4±5.4 vs. 20.2±5.7 ml.kg-1.min-1, p<0.05) in hypoxia. CP was reduced (225±35 vs. 270±49 W, p<0.001) but W’ was unchanged (11.3±2.9 vs. 11.4±2.7 kJ) in hypoxia. The changes in CP/V̇O2max were positively correlated with changes in W’ (r = 0.58, p<0.05). The lower oxygen availability had an impact on aerobic related physiological parameters, but exercise tolerance is similar between hypoxia and normoxia when the relative intensity is matched despite a slower V̇O2 kinetics in hypoxia.
Sekundärdatenanalyse initial vollstationär behandelter Patienten mit Schizophrenie in einem Berliner Modellprojekt (nach § 64b SGB V)
Authors: Budnick Andrea , Kuhnert Ronny , Schmidt Helen , Wienprecht Lars , Kuhlmey Adelheid , Blüher Stefan
Published: January 2021

Ziel der Studie Schizophrenie zählt zu den schwersten psychiatrischen Erkrankungen. Das deutsche Versorgungssystem weist jedoch für diese und andere chronisch psychisch Erkrankte mit einem intensiven Behandlungsbedarf nach wie vor Lücken auf. Der vorliegende Beitrag fokussiert die Veränderung der Versorgung von initial vollstationär behandelten Patienten mit Schizophrenie, die an den St. Hedwig Kliniken in Berlin in einem Modellprojekt nach § 64b SGB V versorgt werden, im Vergleich zu Patienten in der Regelversorgung.

Methodik Die Zielgrößen wurden mittels Routinedaten erfasst. Dabei wurden 3 Patientenkohorten analysiert. Mittels Propensity Score Matching wurde je Kohorte eine Vergleichsgruppe gebildet.

Ergebnisse Es zeigt sich, dass im Modellprojekt die Anzahl der Krankenhausaufenthalte reduziert wurde, die Gesamtverweildauer gesenkt und Gesamtkosten teilweise gesenkt wurden. Zudem verlängerte sich die Dauer bis zur nächsten Rehospitalisierung, während sich die Gesamtzahl der Kontakte zum ambulanten Sektor erhöhte.

Schlussfolgerung Die angestrebte Verlagerung der Versorgung in den ambulanten Bereich wurde für Patienten mit Schizophrenie in diesem Modellprojekt erreicht.
The Rate of Influenza Vaccination after Face-to-Face Interview in Pregnancy
Authors: Orgul Gokcen , Keles Ayse Istek , Yucel Aykan , Sahin Dilek
Published: January 2021

Purpose Most societies recommend routine influenza vaccine to all pregnant women. In Turkey, the Ministry of Health provides the influenza vaccine free of charge to pregnant women during the second and third trimesters. Pregnant women may not be willing to accept vaccination despite their knowledge and attitudes. We aimed to investigate the rate and determining factors of influenza vaccine acceptance after receipt of face-to-face information.

Methods Pregnant women were informed about the benefits of the influenza vaccine and asked if they would get the vaccine.

Results A total of 353 Turkish women were involved, and 191 (54.1%) accepted influenza vaccination. There was no statistically significant difference in terms of maternal age, body mass index, gravida, number of children, socioeconomic status, smoking and occupation between groups. Women in the third trimester had lower vaccination rates compared to first- and second-trimester pregnancies (35.7% vs. 67.7–64.2%). Women with at least a university degree also had lower vaccine uptake rates (58.1% vs. 59.5–36.8%). While 82.2% of women who accepted vaccination believed the benefit of the vaccine to the baby, the rate was 54.9% in the non-vaccinated group. The most common reason for refusal was the belief that influenza was not a serious disease. Vaccination uptake was higher especially for women who understood the benefits of the influenza vaccine for the baby (OR=3.79, 95%Cl=2.34–6.14).

Conclusion Women who had enough information, who had a lower education level, who had a previous history of influenza infection, and who had decided to have their babies vaccinated were more likely to accept influenza vaccine.
Homogeneous Catalyzed Aryl–Aryl Cross-Couplings in Flow
Authors: Nagaki Aiichiro , Ashikari Yosuke
Published: January 2021

Aryl–aryl cross-coupling reactions are important reactions for the production of various biaryl compounds. This short review covers the various aryl–aryl cross-coupling reactions carried out in flow, focusing on the metal species of the aryl nucleophiles used in the cross-coupling reactions.

1 Introduction

2 Suzuki–Miyaura Coupling (B)

3 Migita–Kosugi–Stille Coupling (Sn)

4 Negishi Coupling (Zn)

5 Kumada–Tamao–Corriu Coupling (Mg)

6 Murahashi Coupling (Li)

7 Conclusion
Societies within peace systems avoid war and build positive intergroup relationships
Authors: Fry Douglas P. , Souillac Geneviève , Liebovitch Larry , Coleman Peter T. , Agan Kane , Nicholson-Cox Elliot , Mason Dani , Gomez Frank Palma , Strauss Susie
Published: January 2021

A comparative anthropological perspective reveals not only that some human societies do not engage in war, but also that peaceful social systems exist. Peace systems are defined as clusters of neighbouring societies that do not make war with each other. The mere existence of peace systems is important because it demonstrates that creating peaceful intergroup relationships is possible whether the social units are tribal societies, nations, or actors within a regional system. Peace systems have received scant scientific attention despite holding potentially useful knowledge and principles about how to successfully cooperate to keep the peace. Thus, the mechanisms through which peace systems maintain peaceful relationships are largely unknown. It is also unknown to what degree peace systems may differ from other types of social systems. This study shows that certain factors hypothesised to contribute to intergroup peace are more developed within peace systems than elsewhere. A sample consisting of peace systems scored significantly higher than a comparison group regarding overarching common identity; positive social interconnectedness; interdependence; non-warring values and norms; non-warring myths, rituals, and symbols; and peace leadership. Additionally, a machine learning analysis found non-warring norms, rituals, and values to have the greatest relative importance for a peace system outcome. These results have policy implications for how to promote and sustain peace, cohesion, and cooperation among neighbouring societies in various social contexts, including among nations. For example, the purposeful promotion of peace system features may facilitate the international cooperation necessary to address interwoven global challenges such as global pandemics, oceanic pollution, loss of biodiversity, nuclear proliferation, and climate change.
Source and sink activity of Holcus lanatus in response to absolute and relative supply of nitrogen and phosphorus
Authors: Wang Shuqiong , van Dijk Jerry , de Boer Hugo J. , Wassen Martin J.
Published: January 2021

Mineral nutrients influence photosynthesis and tissue formation; a shift from nitrogen (N)-limited to phosphorus (P)-limited growth induced by high N deposition may change plant growth in terms of physiology and morphology. This experiment showed that absolute and relative N and P supply affected net photosynthesis (source activity) and biomass formation (sink activity), and the relationship between source and sink activities of Holcus lanatus L. under various nutrient treatments. H. lanatus was grown at three N:P ratios (5, 15, 45) with two absolute supply levels of N and P. Between N:P 5 at low level and N:P 45 at high level, and between N:P 45 at low level and N:P 5 at high level, there was a nine-fold difference in N and P supply. Maximum light-saturated net photosynthesis rate (Amax), specific leaf area (SLA), leaf area, and shoot and root biomass were determined during and after the growth process. Amax was minimal at N:P 5 and increased only with increasing absolute N supply. Neither SLA nor leaf area were affected by N:P; increasing absolute P supply significantly increased leaf area. Shoot and root biomass were minimal at N:P 45 and increased dramatically with increasing absolute P supply. Plant biomass was not correlated with Amax. Our results highlight that H. lanatus growth is predominantly controlled by P supply and to a lesser extent by N, whereas net photosynthesis exerted no apparent control on growth under these sink-limited growth conditions. Our findings contribute to understanding of plant growth under sink-limited conditions.
Self‐efficacy and stereotype threat effects on handgrip strength performance in less active people living with HIV
Authors: Gray Laura , d'Arripe‐Longueville Fabienne , Deshayes Maxime , Colson Serge S.
Published: January 2021

People living with HIV (PLHIV) are not physically active enough. As nonexercisers are perceived as less healthy, less active and less strong, it is likely that PLHIV would be subject to a nonexerciser stereotype threat. We looked to elucidate the effect of the emerging nonexerciser stereotype on handgrip strength performance among less active PLHIV. We also sought to observe the modulating role of self‐efficacy in the relationship between stereotype activation and performance.

Eighteen PLHIV were recruited to participate in two experimental sessions in which both a stereotypical context and self‐efficacy were manipulated. Participants performed a handgrip task comprising a 15‐s fatiguing maximal voluntary isometric contraction (MVC) exercise preceded (Pre) and followed (Post) by 5‐s MVCs. In each session, (i.e. high and low self‐efficacy), four experimental conditions (i.e. Control 1; Control 2; Stereotypical; Self‐Efficacy) were performed.

A significant performance decrease of the 15‐s fatiguing MVC exercise was systematically observed when the nonexerciser stereotype was induced (0.01 < p < 0.001). In addition, this performance re‐increased after a high self‐efficacy manipulation (p < 0.001). Pre‐ and post‐ 5‐s MVCs were also significantly depressed after the stereotypical condition (0.01 < p < 0.001) and improved following high self‐efficacy manipulation (p < 0.001).

Our results revealed a detrimental stereotype threat effect on performance during a handgrip task when the nonexerciser stereotype was activated. A high self‐efficacy feedback increased performances significantly whereas no significant difference was observed between the stereotypical and low self‐efficacy conditions. These results indicate that self‐efficacy can modulate the deteriorating effect of a negative exercise stereotype on task performance in less active PLHIV.

Highlights

Handgrip strength was decreased and performance fatigability increased when a negative exercise stereotype was induced.

Performance fatigability and handgrip strength were restored after positive performance feedback was given.

Positive task performance feedback could temper the detrimental effects of a negative stereotypical context among less active people living with HIV.
Linking ecosystem services and economic development for optimizing land use change in the poverty areas
Authors: Xu Yinan , Wei Jianing , Li Zhijun , Zhao Yingxing , Lei Xinyu , Sui Peng , Chen Yuanquan
Published: January 2021

For the sustainable development of human beings and society, it is important to conserve the ecosystems and alleviate poverty in the low agricultural productivity or ecologically vulnerable areas. To avoid the decrease in ecosystem services (ES) under the effects associated with reducing poverty, we need to carefully consider the relationship between land use changes and the economic development in economically poor areas. We selected the Lingqiu County as our study area, which is a national impoverished county in China, and analyzed the impact of poverty alleviation efforts on the ecological and economic sustainability in the region through ES evaluation. The results showed that land use change in the Lingqiu County has not changed the ES significantly during 2007–2016. The gross domestic product (GDP) growth rate (15.81%) during 2001–2016, indicates the effectiveness of the poverty alleviation efforts implemented. The rise in the index of ecological and economic relationship during 2001–2016 (from 0.2389 to 0.3629) maintains in a harmonious coordination situation. Presently, the value of ES has not been converted to market-based benefits, and therefore, it is indispensable to find a marketplace for ES (in an innovative way) to promote the high-quality sustainable development of a local economy.
Golden or pink – Stalin as an embattled memory site
Authors: Kekelia Elene , Reisner Oliver
Published: January 2021

Today, Stalin still haunts the Georgian public. Recent studies have focused solely on “collected” quantitative surveys, rather than “collective” memory on Stalin in Georgia. This paper approaches the Stalin puzzle differently by introducing specific social frameworks and by going beyond a generational analysis. This study illustrates a case of contested memory around Stalin monuments. Drawing on fieldwork (ethnography and interviews) conducted in the Kakheti region and the city of Gori, we analyse how the Stalin cult developed into a memory site. This transformation happened by applying a specific narrative template, which was adapted to different political environments, from the Stalin era until today. We conclude that two opposing interpretations of the narrative template for Stalin as a memory site rely on the same forms, while containing totally different content that we label as an affirmative “golden” variant and an unfavourable “pink” one.
Dynamics of gravitational collapse in the axisymmetric Einstein–Vlasov system
Authors: Ames Ellery , Andréasson Håkan , Rinne Oliver
Published: January 2021

We numerically investigate the dynamics near black hole formation of solutions to the Einstein–Vlasov system in axisymmetry. Our results are obtained using a particle-in-cell and finite difference code based on the (2 + 1) + 1 formulation of the Einstein field equations in axisymmetry. Solutions are launched from non-stationary initial data and exhibit type I critical behaviour. In particular, we find lifetime scaling in solutions containing black holes, and support that the critical solutions are stationary. Our results contain examples of solutions that form black holes, perform damped oscillations, and appear to disperse. We prove that complete dispersal of the solution implies that it has nonpositive binding energy.
Strong gravitational lensing by DHOST black holes
Authors: Chagoya Javier , Ortiz C , Rodríguez Benito , Roque Armando A
Published: January 2021

The gravitational deflection of light in the strong field limit is an important test for alternative theories of gravity. However, solutions for the metric that allow for analytic computations are not always available. We implement a hybrid analytic-numerical approximation to determine the deflection angle in static, spherically symmetric spacetimes. We apply this to a set of numerical black hole solutions within the class of modified gravity theories known as degenerate higher order scalar–tensor theories (DHOST). Comparing our results to a more time consuming full numerical integration, we find that we can accurately describe the deflection angle for light rays passing at arbitrary distances from the photon sphere with a combination of two analytic-numerical approximations. Furthermore, we find a range of parameters where our DHOST black holes predict strong lensing effects whose size is comparable with the uncertainty in the properties of the supermassive black hole in M87 reported by the event horizon telescope, showing that strong lensing is a viable alternative to put constraints on these models of modified gravity.
On the language of elementary mechanics
Authors: Young-Ziegler Ariel , Pérez Patricia E , Binder P-M
Published: January 2021

We performed word frequency analysis of the mechanics portion of an algebra-based introductory physics text. We identified about 400 physics and auxiliary words that constitute the core vocabulary of this subject. We present and discuss our findings especially as they inform physics instruction and communication in English, indigenous, and sign languages. This includes the Hawaiian language, our initial motivation for undertaking this work.
Oscillator strengths and integral cross-sections of the valence-shell excitations of CH3Cl studied by fast electron scattering
Authors: Li Tian-Jun , Xu Yuan-Chen , Du Xiao-Jiao , Wang Li-Han , Ma Zi-Ru , Wang Shu-Xing , Zhu Lin-Fan
Published: January 2021

The generalized oscillator strengths (GOSs) of the valence-shell excitations of CH3Cl have been determined at an incident electron energy of 1500 eV and an energy resolution of about 70 meV. The momentum transfer dependence behaviors of the GOSs of the valence-shell excitations have been carefully analyzed, and the A band shows a strong dipole-forbidden characteristic. By extrapolating the GOSs to the limit of a zero squared momentum transfer, the optical oscillator strengths have been obtained, which provide an independent cross-check for the previous experimental and theoretical results. The BE-scaled integral cross sections (where B is the binding energy and E is the excitation energy) of the valence-shell excitations of CH3Cl have been derived systematically from the threshold to 5000 eV with the aid of a BE-scaling method. The results provide the fundamental spectroscopic data of CH3Cl and have important applications in photochemical modeling for atmospheric physics.
Underwater imaging enhancement based on a polarization filter and histogram attenuation prior
Authors: Hu Haofeng , Qi Pengfei , Li Xiaobo , Cheng Zhenzhou , Liu Tiegen
Published: January 2021

Underwater images always suffer from low contrast and inaccurate colors due to scattering and absorption by particles when the target light propagates through turbid water. In this paper, we first found that a lot of intensity space is occupied by fewer pixels, called ‘tails’, on both sides of the histograms for the red, green and blue channels of the image. Based on this histogram attenuation prior and taking account of the advantage of a polarization filter we proposed an effective polarimetric recovery method to enhance the underwater image quality, which includes a specially designed histogram processing method, named ‘cut-tail histogram stretching’. This processing overcomes the limitation of traditional histogram-based methods and can further improve the restoration performance. The experimental results corresponding to underwater scenes with different turbidities and colors show that the proposed method can simultaneously enhance the image contrast and reduce the color distortion to some extent, and thus realize clear underwater vision.
Stability of electron–hole liquid in quantum wells
Authors: Vasilchenko A A
Published: January 2021

Density functional theory is used to calculate the energy of electron–hole liquid and the equilibrium density of electron-hole pairs in quantum wells. Nonlinear Kohn–Sham equations for electrons and holes are solved numerically. The influence of the depth and width of the quantum well, the ratio of the hole and electron masses, and the spin splitting of the hole band on the properties of electron–hole liquid is studied. The critical temperature of electron–hole liquid in quantum wells is estimated. Good agreement between the calculations and experimental results is obtained.
Half-auxetic effect and ferroelasticity in a two-dimensional monolayer TiSe
Authors: Liu Ziyuan , Pan Jinbo , Zhang Yan-Fang , Du Shixuan
Published: January 2021

Two-dimensional (2D) materials with both auxetic effect and ferroelasticity are rare, however, have great application potential in next generation microelectromechanical and nanoelectronic devices. Here, we report the findings of an extraordinary combination half-auxetic effect and ferroelasticity in a single p2mm-type TiSe monolayer by performing first-principles calculations. The unique half-auxetic effect, namely the material expand laterally under both uniaxial tensile strain, and compressive strain, is reported and explained by considering both the nearest and the next-nearest interactions. The ferroelasticity is stemming from the degeneracy breaking of the 3d-orbitals of Ti atoms in a distorted tetrahedron crystal field, or the so-called Jahn–Teller effect. The results provide a guideline for the future design of novel 2D multiple functional materials at the nanoscale.
Triple-temperature readout in luminescence thermometry with Cr3+-doped Mg2SiO4 operating from cryogenic to physiologically relevant temperatures
Authors: Ristić Zoran , Đorđević Vesna , Medić Mina , Kuzman Sanja , Sekulić Milica , Antić Željka , Dramićanin Miroslav D
Published: January 2021

Cr3+-doped Mg2SiO4 orthorhombic nanoparticles are synthesized by a combustion method. The 3d3 electron configuration of the Cr3+ ion results in the deep-red emission from optical transitions between d–d orbitals. Two overlapping emissions from the Cr3+ spin-forbidden 2Eg→ 4A2g and the spin-allowed 4T2g→ 4A2g electronic transitions are influenced by the strong crystal field in Mg2SiO4 and, thus, are suitable for ratiometric luminescence thermometry. The temperature-induced changes in Cr3+-doped Mg2SiO4 emission are tested for use in luminescence thermometry from cryogenic to physiologically relevant temperatures (10–350 K) by three approaches: (a) temperature-induced changes of emission intensity; (b) temperature-dependent luminescence lifetime; and (c) temperature-induced changes of emission band position. The second approach offers applicable thermometry at cryogenic temperatures, starting from temperatures as low as 50 K, while all three approaches offer applicable thermometry at physiologically relevant temperatures with relative sensitivities of 0.7% K−1 for emission intensity, 0.8% K−1 for lifetime and 0.85% K−1 for band position at 310 K.
Multi-Δt approach for peak-locking error correction and uncertainty quantification in PIV
Authors: Adatrao Sagar , Bertone Michele , Sciacchitano Andrea
Published: January 2021

A novel approach is devised for the quantification of systematic uncertainty due to peak locking in particle image velocimetry (PIV), which also leads to correction of the peak-locking errors. The approach, applicable to statistical flow properties such as time-averaged velocity and Reynolds stresses, relies on image recordings with multiple time separations Δt and a least-squares regression of the measured quantities. In presence of peak locking, the measured particle image displacement is a non-linear function of Δt due to the presence of measurement errors which vary non-linearly with the sub-pixel particle image displacement. Additionally, the measured displacement fluctuations are a combination of the actual flow fluctuations and the measurement error. When the image recordings are acquired with multiple Δt’s, a least-squares regression among the statistical results yields a correction where systematic errors due to peak locking are significantly diminished. The methodology is assessed for planar PIV measurements of the flow over a NACA0012 airfoil at 10 degrees angle of attack. Reference measurements with much larger Δt than the Δt’s of the actual measurements, such that relative peak-locking errors are negligible for the former, are used to assess the validity of the proposed approach.
A molecular dynamics study on the local mobility of cis-polyisoprene within the mixed glassy/rubbery states induced by graphene planes
Authors: Sutthibutpong Thana
Published: January 2021

The glass transition behavior of a simulated model consisting of cis-1,4-polyisoprene nanofilm confined within parallel graphene planes was visualized through chain mobility statistics. Firstly, simulated annealing molecular dynamics (MD) simulations were performed for a system of bulk polyisoprene and the polyisoprene nanofilm within parallel graphene planes at two different gap sizes. The glass transition temperature (T
g) and the critical density of bulk polyisoprene were then calculated. The critical density was used to compare with the local density of the confined polyisoprene segments. The mixed glassy/rubbery states were found at temperatures higher than the bulk T
g. It was also shown that bulk modulus was increased when graphene planes are present and was further increased when the gap between graphene planes became narrow, and a ‘glassy bridge’ was formed by the highly confined nanofilm with highly-ordered polymer chains. Then, local mobility of each polyisoprene chain segment was quantified through the square displacement (SD) after a 1 ns motion. Local glass transition within any region was determined by whether local SD was lower than the critical mean square displacement (MSD0) of bulk polyisoprene, which was in the ‘glassy regime.’ The analysis results showed that decreasing the temperature and reducing the gap between graphene planes increased the proportion of chain segments in the glassy regime and were in concurrence with the increased bulk modulus.
A low-T
c superconducting modification of Th4H15 synthesized under high pressure
Authors: Wang N N , Shan P F , Chen K Y , Sun J P , Yang P T , Ma X L , Wang B S , Yu X H , Zhang S , Chen G F , Cheng J-G , Dong X L , Chen X H , Zhao Z X
Published: January 2021

Among the metal hydrides, Th4H15 is the first reported superconductor with a relatively high T
c ≈ 8 K at ambient pressure. Here we report on the synthesis and characterization of a low-T
c superconducting modification of Th4H15, which is obtained via hydrogenating Th metal at 5 GPa and 800 °C by using the ammonia borane as the hydrogen source. Measurements of resistivity, magnetic susceptibility, and specific heat confirm that the obtained Th4H15 sample shows a bulk superconducting transition at T
c ≈ 6 K, which is about 2 K lower than that reported previously. Various characteristic superconducting parameters have been extracted for this compound and unusual lattice dynamics were evidenced from the specific-heat analysis.
Using a Josephson junction as an effective on-chip temperature sensor
Authors: Durandetto Paolo , Sosso Andrea
Published: January 2021

Temperature sensing and control are essential in experiments running in cryocooled systems, as with the case of liquid helium-free superconducting devices. A Josephson junction as on-chip temperature sensor operated in ac provides the highest sensitivity and minimal power loading to the cryogenic environment, thanks to the noise rejection of lock-in detection. To demonstrate the advantages of on-chip sensing, we tested it with a Josephson voltage standard array in cryocooler and compared with the conventional case of a sensor on the cold surface of the refrigerator, showing that the power dissipated within the chip may further increment the device temperature up to some tenths of kelvin. An ac Josephson junction sensor is proven to be capable of directly stabilizing the temperature of the superconductive circuit from fluctuations of dissipated power during operation. Reliability issues related to flux trapping are discussed and solutions are proposed suited to different applications. Overall, on-chip control with ac Josephson temperature sensing has the advantage of avoiding the complexities in minimization of cryogenic thermal links, virtually reducing to zero the contact resistance and keeping the operating temperature of the superconductor constant, independently of instantaneous operating power.
Second-order delay ordinary differential equations, their symmetries and application to a traffic problem
Authors: Dorodnitsyn Vladimir A , Kozlov Roman , Meleshko Sergey V , Winternitz Pavel
Published: January 2021

This article is the third in a series, the aim of which is to use Lie group theory to obtain exact analytic solutions of delay ordinary differential systems (DODSs). Such a system consists of two equations involving one independent variable x and one dependent variable y. As opposed to ordinary differential equations (ODEs) the variable x figures in more than one point (we consider the case of two points, x and x
−). The dependent variable y and its derivatives figure in both x and x
−. Two previous articles were devoted to first-order DODSs, here we concentrate on a large class of second-order ones. We show that within this class the symmetry algebra can be of dimension n with 0 ⩽ n ⩽ 6 for nonlinear DODSs and must be infinite-dimensional for linear or linearizable ones. The symmetry algebras can be used to obtain exact particular group invariant solutions. As a specific application we present some exact solutions of a DODS model of traffic flow.
A Tamm plasmon-porous GaN distributed Bragg reflector cavity
Authors: Pugh J R , Harbord E G H , Sarua A , Fletcher P S , Tian Y , Wang T , Cryan M J
Published: January 2021

This paper reports on design, measurement and optimisation of a Tamm plasmon metal-distributed Bragg reflector (DBR) cavity for use in the green part of the visible spectrum. It uses an optimised silver layer thickness and a porous DBR created using a novel electro-chemical etching technique. This device has applications in low-cost lasers, photodetectors, and photoconductive switches for the visible wavelength range.
Cadmium stannate conductive layer with high optical transmittance and tunable work function
Authors: Zhu Ziyao , Du Zhongming , Liu Xiangxin , Zhang Yufeng , Wu Qiuchen , Lin Xinlu
Published: January 2021

200 nm cadmium stannate (Cd2SnO4) transparent conductive layer films with a sheet resistance of 6.35 Ω/sq and resistivity of 1.27 × 10−4 Ω · cm are deposited by magnetron sputtering coupling with adjustable target bias voltage followed by 620 °C 30 min annealing. The lowest resistivity of Cd2SnO4 films reported before was 1.28 × 10−4 Ω · cm, achieved with 510 nm Cd2SnO4. The average transmission rate of 200 nm sputtering Cd2SnO4 films between 400–800 nm is 94%. The deposition rate increase target bias voltage can the and electrical performance of Cd2SnO4 films. The surface work function of Cd2SnO4 films is also tunable by target bias voltage. The Cd2SnO4 phonon spectrum and phonon density of states combined with Raman microscope shows the Cd2SnO4 films with most ideal electric properties has a identical phonon response. XPS shows the chemical component of as-deposited Cd2SnO4 films and Cd2SnO4 films after annealing with 120 V target bias voltage is Cd2.03SnO6.36 and Cd1.25SnO4.15, respectively, which is contrary to the general conclusions that interstitial cadmium atoms and oxygen vacancies are the main self-doping defects in Cd2SnO4 films.
Spectroscopy and critical quantum thermometry in the ultrastrong coupling regime
Authors: Salado-Mejía M , Román-Ancheyta R , Soto-Eguibar F , Moya-Cessa H M
Published: January 2021

We present an exact analytical solution of the anisotropic Hopfield model, and we use it to investigate in detail the spectral and thermometric response of two ultrastrongly coupled quantum systems. Interestingly, we show that depending on the initial state of the coupled system, the vacuum Rabi splitting manifests significant asymmetries that may be considered spectral signatures of the counterintuitive decoupling effect. Using the coupled system as a thermometer for quantum thermodynamics applications, we obtain the ultimate bounds on the estimation of temperature that remain valid in the ultrastrong coupling regime. Remarkably, if the system performs a quantum phase transition, the quantum Fisher information exhibits periodic divergences, suggesting that one can have several points of arbitrarily high thermometric precision for such a critical quantum sensor.
2D materials and their heterostructures for photocatalytic water splitting and conversion of CO2 to value chemicals and fuels
Authors: Shanker G Shiva , Biswas Abhijit , Ogale Satishchandra
Published: January 2021

The rapidly increasing global energy consumption utilizing conventional polluting fuels has been putting enormous stress on the health of our environment and thereby the long term sustainability of the animal and plant life on our planet. The world clearly needs to move rapidly to the alternative sources of environment-friendly, carbon-neutral, clean and renewable energy. To this end, amongst the promising strategies being pursued, one of the best approaches is to produce hydrogen energy from water by using sunlight, with unlimited available resource of both water and sunlight. Concurrently, there is also an emergent need to control CO2 emissions by reducing them to valuable fuels or chemicals using sunlight. For both these goals, it is essential to have efficient, robust and affordable photocatalysts. The early emphasis on semiconductor photocatalysts along with expensive noble-metals co-catalysts has prevented the speedy advance of this energy technology. Extensive efforts are now being expended on designing high-performance photocatalysts based on emergent functional materials endowed with a fascinating set of physical and chemical properties. Towards this end, two-dimensional (2D) materials and their heterostructures have been attracting significant attention lately as potentially viable candidates owing to their unique, and highly tunable optical and electronics functionalities, which are technically adequate for the efficient hydrogen production and conversion of CO2 to fuels. In this topical review, we address the recent progress made in the domain. We believe that by virtue of the uniquely distinct characteristics of their electronic density of states, surface states, high surface area, and diverse possibilities of innovative surface chemical engineering, the 2D materials hold a great promise for facilitating economically viable renewable/clean energy harvesting solution(s) on commercial-scale, thereby accomplishing the urgent task of ensuring the future energy security for the world.
mlr3proba: an R package for machine learning in survival analysis
Authors: Sonabend Raphael , Király Franz J. , Bender Andreas , Bischl Bernd , Lang Michel
Published: January 2021

As machine learning has become increasingly popular over the last few decades, so too has the number of machine-learning interfaces for implementing these models. Whilst many R libraries exist for machine learning, very few offer extended support for survival analysis. This is problematic considering its importance in fields like medicine, bioinformatics, economics, engineering and more. mlr3proba provides a comprehensive machine-learning interface for survival analysis and connects with mlr3’s general model tuning and benchmarking facilities to provide a systematic infrastructure for survival modelling and evaluation.

Availability and implementation

mlr3proba is available under an LGPL-3 licence on CRAN and at https://github.com/mlr-org/mlr3proba, with further documentation at https://mlr3book.mlr-org.com/survival.html.
Genomic and niche divergence in an Amazonian palm species complex
Authors: Bacon Christine D , Roncal Julissa , Andermann Tobias , Barnes Christopher J , Balslev Henrik , Gutiérrez-Pinto Natalia , Morales Hernán , Núñez-Avelleneda Luis Alberto , Tunarosa Natalia , Antonelli Alexandre
Published: January 2021

Environmental heterogeneity across the landscape can cause lineage divergence and speciation. The Geonoma macrostachys (Arecaceae) species complex has been proposed as a candidate case of ecological speciation in Amazonia due to evidence of habitat partitioning and pre-zygotic reproductive barriers between co-occurring morphotypes at a local scale. In this study, we provide a continent-wide perspective of the divergence patterns in G. macrostachys by integrating data from morphological traits, target sequence capture, climate, soil and reproductive biology. A morphometric analysis revealed four morphogroups, defined by traits related to leaf shape. A coalescence-based phylogenetic analysis did not recover the morphogroups as monophyletic, indicating independent evolution of leaf shape across geographical space. We demonstrate scale-dependent habitat differentiation for two of the morphogroups, in which segregation driven mostly by climate was complete at the regional scale but incomplete at the continental scale. Contrary to previous evidence of reproductive isolation in the form of different pollinators and flowering times between sympatric G. macrostachys forms in Peru and Ecuador, these were not found in Colombia, suggesting reproductive barriers have evolved multiple times across its geographical range. Taken together, our findings suggest that ecological divergence and local adaptation is driving diversification in G. macrostachys, and that hyperdiverse regions such as Amazonia are probable arenas for ecological divergence in sympatry.
Extremely rapid stone formation in cystinuria: look out for dietary supplements!
Authors: Gillion Valentine , Saussez Thibaud-Pierre , Van Nieuwenhove Sandy , Jadoul Michel
Published: January 2021

Cystinuria is an autosomal recessive disease characterized by recurrent nephrolithiasis. The prevention of new stones is based on diluting and alkalinizing urine, as well as a low salt and moderate protein intake. The avoidance of food rich in methionine (the precursor of cystine) is also advocated. We report the case of a young adult adherent to the preventative strategy who was stone-free and within months formed a large stone. This coincided with the recent intake of a dietary supplement containing both cystine and methionine. Patients and physicians should be aware of the potential harm of such supplements in patients with cystinuria.