bluuebunny/crossref_metadata_2025_split huggingface dataset:
Psychological correlates of insomnia in professional soccer players: An exploratory study
Authors: Ballesio Andrea , Vacca Mariacarolina , Bacaro Valeria , Benazzi Adriano , De Bartolo Paola , Alivernini Fabio , Lucidi Fabio , Lombardo Caterina , Baglioni Chiara 
Published: February 2021

ABSTRACTSleep promotes health, well‐being, recovery and athletic performance. As a consequence, sleep problems in athletes may have detrimental effects. Previous investigations showed that professional athletes often reported to suffer of poor sleep quality and insomnia (e.g. difficulties falling asleep and/or maintaining sleep). However, psychological variables exacerbating and maintaining insomnia in professional athletes as well as its mechanistic pathways are still largely unknown. Available literature mostly focused on effects of sport‐related variables, such as evening training and stimulant consumption on athletes’ sleep. Instead, the contribution of cognitive and emotional variables globally associated with insomnia in athletes in clinical models has been largely neglected. To address these limitations, this study explored the associations between emotional experience, pre‐sleep arousal, pre‐sleep worry and rumination and insomnia severity in a sample of 210 (25.93 ± 6.68 years) male professional soccer players. Bivariate correlations, multiple regression, and structural equation modelling with manifest variables (path analysis) were computed. Results showed that insomnia severity was associated with stimulants consumption, pre‐sleep arousal, negative emotions, positive emotions, and pre‐sleep worry/rumination (all p < .05). Path analysis showed that relationship between stimulant consumption, emotional experience, worry/rumination and insomnia was mediated by pre‐sleep arousal (p < .05). Our results suggest that preventive and interventional studies in professional soccer players would benefit from considering global cognitive‐emotional variables as targets of interventions.
Highlights
Insomnia was associated with greater stimulants consumption, pre‐sleep arousal, negative emotions, pre‐sleep worry/rumination, and lower positive emotions.
Path analysis showed that pre‐sleep arousal mediated the relationship between stimulant consumption, emotional experience, worry/rumination and insomnia severity.
Cognitive‐emotional and behavioural factors as well as sport‐related variables were important predictors of insomnia in professional soccer players.
Heart rate rather than heart rate variability is better associated with cardiorespiratory fitness in adults
Authors: Plaza‐Florido Abel , Amaro‐Gahete Francisco J. , Acosta Francisco M. , Sacha Jerzy , Alcantara Juan M.A. 
Published: February 2021

ABSTRACTThis study aimed to examine the association of heart rate (HR) and heart rate variability (HRV) with cardiorespiratory fitness (CRF) in adults. This cross‐sectional study included 204 participants: 132 young adults (67% women; 22.3 ± 2.3 years) and 72 middle‐aged adults (53% women; 53.2 ± 5 years). HR and HRV were measured using a Polar RS800CX heart rate monitor. CRF was assessed using a metabolic cart during an incremental test. HR was negatively associated with CRF relative to body weight (BW) in young adults adjusting for sex, age, and physical activity (β ranged from −0.200 to −0.195; all P ≤ 0.022). These associations disappeared after including fat mass as a covariate (all P ≥ 0.106) while remained significant after adjusting for fat‐free mass (FFM; all P ≤ 0.008). Neither HR nor HRV variables were associated with CRF expressed as absolute values or relative to FFM in young and middle‐aged adults after adjusting for the abovementioned covariates (all P ≥ 0.074). Our results suggest that HR rather than HRV is better associated with CRF relative to BW in young adults. However, this association seems to be explained by the inclusion of fat mass in the calculation of CRF relative to BW.

Highlights
Heart rate and heart rate variability variables have been associated with cardiorespiratory fitness.
Our present results, and previous literature, suggest that the “simple” measurement of the heart rate could be easier to obtain and interpret than the heart rate variability variables.
The heart rate variable rather than the heart rate variability variables is better associated with cardiorespiratory fitness relative to body weight in healthy young adults.
Quantum fluctuations of the compact phase space cosmology
Authors: Artigas Danilo , Crowe Sean , Mielczarek Jakub 
Published: February 2021

Abstract
In the recent article (2019 Phys. Rev. D
100 043533) a compact phase space generalization of the flat de Sitter cosmology has been proposed. The main advantages of the compactification is that physical quantities are bounded, and the quantum theory is characterized by finite dimensional Hilbert space. Furthermore, by considering the

S

2

phase space, quantum description is constructed with the use SU(2) representation theory. The purpose of this article is to apply effective methods to analyze quantum dynamics of the model at the semi-classical regime. The analysis is performed both without prior solving of the quantum constraint and by extracting physical Hamiltonian of the model. At the effective level, the results of the two procedures are shown to be equivalent. We find a nontrivial behavior of the fluctuations around the recollapse of the Universe, which is distinct from what is found after quantization with the standard flat phase space. The behavior is reflected at the level of the modified Friedmann equation with quantum back-reaction effects, which is derived. Finally, a relation between quantum fluctuations in the minisuperspace model under consideration and the Bousso bound has been found. It has been shown that the Bousso bound can be violated for certain choices of semiclassical states.
Antiferromagnetism of CoO-NiO bilayers studied by XMLD spectroscopy
Authors: Jena Bibhuti Bhusan , Mandal Suman , Menon Krishnakumar S R 
Published: February 2021

Abstract
CoO-NiO epitaxial bilayer system grown on MgO(001) substrate is investigated using x-ray magnetic linear dichroism (XMLD) spectroscopy with varying CoO overlayer thickness. An analysis of the Ni L
2 edge XMLD spectra using anisotropic XMLD formulation within a two-domain model reveals that the Ni moments undergo a spin reorientation with increasing CoO thickness. Such a spin reorientation is attributed to the competing magnetic interactions at both the NiO film interfaces, suggesting the existence of a sharp horizontal domain wall separating the in-plane and out-of-plane NiO domains. Our study also demonstrates a possible way to investigate the spin-structure along the thickness within the same chemical structure using a model-based approach, in a noninvasive manner.
Experimental study of the effect of water vapor on dynamics of a high electric field non-equilibrium diffuse discharge in air
Authors: Brisset A , Tardiveau P , Gazeli K , Bournonville B , Jeanney P , Ouaras K , Magne L , Pasquiers S 
Published: February 2021

Abstract
We report results on the influence of relative humidity (RH) on the propagation speed, the intensity of the emitted light, the energy and the gas temperature of a pin-to-plane nanosecond pulsed discharge at atmospheric pressure in synthetic air. The discharge is generated under very high overvoltage (several tens of kilovolts) so that it propagates with a voluminous, diffuse, and stable pattern. It is shown that the water vapor content has a strong impact on the discharge dynamics for gas mixtures with high RH and for the highest electric field values. In particular, for voltage pulse amplitudes higher than 65 kV and RH higher than 30%, the propagation abruptly slows down and the light intensity profiles show a stronger emission at the pin which weakens in the rest of the gap. The electric energy is slightly lower in humid air, independently of water vapor concentration. Also, time and spatially resolved gas temperature measurements carried out for different voltages show a late and significant heating at the pin whatever the water vapor content. An evaluation of the energy consumed in fast heating processes is proposed, showing an increased energy consumption at the pin in highly humid air. Besides, the hypotheses allowing for the consideration of the rotational temperature of the second positive system (SPS) of nitrogen (N2(SPS)) as the gas temperature under high electric field conditions are discussed.
Strong magnetization and anisotropy of Mn5Ge3 thin films on Ge(001)
Authors: Alvídrez-Lechuga Adriana , Antón Ricardo López , Gutiérrez-Pérez Rocío M , Fuentes-Montero Maria E , Espinosa-Magaña Francisco , Holguín-Momaca José T , Andrés Juan Pedro , Olive-Méndez Sion F 
Published: February 2021

Abstract
We report on the growth of Mn5Ge3 thin films on Ge(001) substrates following two methods: solid phase epitaxy (SPE) and reactive deposition epitaxy (RDE). We have varied the thickness of the films, in order to study the magnetization and anisotropy evolution. A strongly enhanced magnetization of 1580 kA m−1, compared to 1200 ± 150 kA m−1 for films grown on Ge(111), has been measured on ultrathin films of 5 nm grown by RDE. Thicker films exhibited magnetizations <750 kA m−1. The films grown by SPE also exhibit strong magnetization of 1490 kA m-1 and a drop of magnetization by increasing the film thickness. The effective magnetic anisotropy exhibits a more complex behavior: increases on the SPE films and decreases on the RDE films while increasing the thickness of the films. Magnetostatic and interfacial anisotropies were considered and calculated. The results are discussed in terms of the growth methods and microstructure of the films.
High-pressure effects on superconducting properties and crystal structure of Bi-based layered superconductor La2O2Bi3Ag0.6Sn0.4S6
Authors: Liu Supeng , Matsumoto Ryo , Jha Rajveer , Yamashita Aichi , Kawaguchi Saori I , Goto Yosuke , Takano Yoshihiko , Mizuguchi Yoshikazu 
Published: February 2021

Abstract
The effects of pressure on the superconducting properties of a Bi-based layered superconductor La2O2Bi3Ag0.6Sn0.4S6, which possesses a four-layer-type conducting layer, have been studied through the electrical resistance and magnetic susceptibility measurements. The crystal structure under pressure was examined using synchrotron x-ray diffraction at SPring-8. In the low-pressure regime, bulk superconductivity with a transition temperature T
c of ∼4.5 K was induced by pressure, which was achieved by in-plane chemical pressure effect owing to the compression of the tetragonal structure. In the high-pressure regime above 6.4 GPa, a structural symmetry lowering was observed, and superconducting transitions with a T
c ∼ 8 K were observed. Our results suggest the possible commonality on the factor essential for T
c in Bi-based superconductors with two-layer-type and four-layer-type conducting layers.
Compensation for mobile carrier magnetic interference in a SQUID-based full-tensor magnetic gradiometer using the flower pollination algorithm
Authors: Wang Mingchao , Lin Jun , Yue Liangguang , Wang Yi , Zhao Jing 
Published: February 2021

Abstract
The improving quality of ultra-sensitive superconducting quantum interference devices has led to the construction of advanced full-tensor magnetic gradiometers (FTMGs) integrated on mobile carriers such as aircraft, vehicles and ships. FTMGs measure the smallest spatial magnetic gradients, possessing many practical advantages compared to conventional scalar surveys and three-component surveys. However, the magnetic interference field caused by the magnetic sources associated with the carrier significantly decreases the precision of measurement. In this paper, a novel method is proposed to compensate for the magnetic interference field. Specifically, a mathematical model containing compensation coefficients of the mobile FTMG system is constructed by extending the Tolles–Lawson model. By formulating the task into nonlinear problems, unknown compensation coefficients in the model can be solved by the flower pollination algorithm, which has the advantages of insensitivity to iterative initial values, less parameter tuning and strong global search abilities. Both the finite-element simulation results based on COMSOL Multiphysics and the results of a field experiment show that the proposed method provides a useful way for the optimal estimation of compensation coefficients and the reduction of the magnetic interference field.
UV response characteristics of mixed-phase MgZnO thin films with different structure distributions, high Iuv/Idark ratios, and fast speed MgZnO UV detectors with tunneling breakdown mechanisms
Authors: Han Shun , Xia H , Lu Y M , Liu W J , Xu W Y , Fang M , Cao P J , Zhu D L 
Published: February 2021

Abstract
High-performance ultraviolet (UV) detectors with both high responses and fast speeds are hard to make on homogeneous crystal semiconductor materials. Here, the UV response characteristics of mixed-phase MgZnO thin films with different internal structure distributions are studied. The mixed-phase MgZnO-based detector with the given crystal composition has a high response at both deep UV light (96 A W−1 at 240 nm) and near UV light (80 A W−1 at 335 nm). Meanwhile, because of the quasi-tunneling breakdown mechanism within the device, the high-response UV detector also shows a fast response speed (tr = 0.11 μs) and recovery speed (td1 = 26 μs) at deep UV light, which is much faster than both low-response mixed-phase MgZnO-based UV detectors with other structure constitutions and reported high-response UV devices on homogenous crystal materials. The Idark of the device is just 4.27 pA under a 5 V bias voltage, so the signal-to-noise ratio of the device reached 23852 at 5.5 uW cm−2 235 nm UV light. The new quasi-tunneling breakdown mechanism is observed in some mixed-phase MgZnO thin films that contain both c-MgZnO and h-MgZnO parts, which introduce a high response, signal-to-noise ratio, and fast speed into mixed-phase MgZnO-based UV detectors at weak deep UV light.
Stereolithography (SLA) 3D printing of carbon fiber-graphene oxide (CF-GO) reinforced polymer lattices
Authors: Xiao Ran , Ding Mingyang , Wang Yuejiao , Gao Libo , Fan Rong , Lu Yang 
Published: February 2021

Abstract
Insufficient mechanical properties of stereolithography (SLA)-printed architected polymer metamaterial limits its wide applications such as in the areas of biomedicine and aerospace. One effective solution is to reinforce the structures with micro- or nano- fibers/particles, but their interfaces are critical for the reinforcement. In this work, a carbon fiber-graphene oxide (CF-GO) polymer composite resin and a mild annealing postprocess have been rationally designed and applied into the manufacturing of oct-truss (OCT) lattices. In situ carbon fiber pulling-out experiment was conducted to exhibit the improve effect of GO on the crosslink of the CF and the polymer matrix interface. We found that the maximum reinforcement was realized when the CF-GO (CF: GO is about 3: 1) content is about 0.8 wt%, followed with annealing. Compared with pure polymer lattices, the compression strength of the CF-GO polymer OCT lattices has been significantly increased from ∼0.22 to ∼2.4 MPa, almost 10 times enhancement. Importantly, the compression strength of the CF-GO polymer OCT lattice (3.08 MPa) further increased by ∼30% after optimized annealing. This work suggests an efficient reinforce strategy for SLA-printed metamaterials, and thus can be valuable for advancing various practical applications of mechanical metamaterials.
Dynamic measurement of the elastic constant of an helicoidal spring by a smartphone
Authors: Agliolo Gallitto Aurelio , Battaglia Onofrio Rosario , Fazio Claudio 
Published: February 2021

Abstract
We describe an educational activity that can be done by using smartphones to collect data in physics experiments aimed to measure the oscillating period of a spring-mass system and the elastic constant of the helicoidal spring by the dynamic method. Results for the oscillating period and for the elastic constant of the spring agree very well with measurements obtained by different methods. We also discuss the error analysis that can be done in an introductory physics laboratory at undergraduate level.
Effects on skin dose from unwanted air gaps under bolus in an MR-guided linear accelerator (MR-linac) system
Authors: Huang Chen-Yu , Yang Bin , Lam Wai Wang , Tang Ka Keung , Li Ting Chuan , Law Wai Kong , Cheung Kin Yin , Yu Siu Ki 
Published: February 2021

Abstract
Bolus is commonly used in MV photon radiotherapy to increase superficial dose and improve dose uniformity for treating shallow lesions. However, irregular patient body contours can cause unwanted air gaps between a bolus and patient skin. The resulting dosimetric errors could be exacerbated in MR-Linac treatments, as secondary electrons generated by photons are affected by the magnetic field. This study aimed to quantify the dosimetric effect of unwanted gaps between bolus and skin surface in an MR-Linac. A parallel-plate ionization chamber and EBT3 films were utilized to evaluate the surface dose under bolus with various gantry angles, field sizes, and different air gaps. The results of surface dose measurements were then compared to Monaco 5.40 Treatment Planning System (TPS) calculations. The suitability of using a parallel-plate chamber in MR-Linac measurement was validated by benchmarking the percentage depth dose and output factors with the microDiamond detector and air-filled ionization chamber measurements in water. A non-symmetric response of the parallel-plate chamber to oblique beams in the magnetic field was characterized. Unwanted air gaps significantly reduced the skin dose. For a frontal beam, skin dose was halved when there was a 5 mm gap, a much larger difference than in a conventional linac. Skin dose manifested a non-symmetric pattern in terms of gantry angle and gap size. The TPS overestimated skin dose in general, but shared the same trend with measurement when there was no air gap, or the gap size was larger than 5 mm. However, the calculated and measured results had a large discrepancy when the bolus-skin gap was below 5 mm. When treating superficial lesions, unwanted air gaps under the bolus will compromise the dosimetric goals. Our results highlight the importance of avoiding air gaps between bolus and skin when treating superficial lesions using an MR-Linac system.
Large-scale screening to distinguish between COVID-19 and community-acquired pneumonia using infection size-aware classification
Authors: Shi Feng , Xia Liming , Shan Fei , Song Bin , Wu Dijia , Wei Ying , Yuan Huan , Jiang Huiting , He Yichu , Gao Yaozong , Sui He , Shen Dinggang 
Published: February 2021

Abstract
The worldwide spread of coronavirus disease (COVID-19) has become a threat to global public health. It is of great importance to rapidly and accurately screen and distinguish patients with COVID-19 from those with community-acquired pneumonia (CAP). In this study, a total of 1,658 patients with COVID-19 and 1,027 CAP patients underwent thin-section CT and were enrolled. All images were preprocessed to obtain the segmentations of infections and lung fields. A set of handcrafted location-specific features was proposed to best capture the COVID-19 distribution pattern, in comparison to the conventional CT severity score (CT-SS) and radiomics features. An infection size-aware random forest method (iSARF) was proposed for discriminating COVID-19 from CAP. Experimental results show that the proposed method yielded its best performance when using the handcrafted features, with a sensitivity of 90.7%, a specificity of 87.2%, and an accuracy of 89.4% over state-of-the-art classifiers. Additional tests on 734 subjects, with thick slice images, demonstrates great generalizability. It is anticipated that our proposed framework could assist clinical decision making.
Reversal of laser wake phase velocity generates high-power broadband Cherenkov signal
Authors: Kalmykov Serge , Elle Jennifer , Schmitt-Sody Andreas 
Published: February 2021

Abstract
As a femtosecond terawatt laser pulse propagates along a positive density gradient within a stratified plasma column, it drives a low-frequency electromagnetic wake wave, the period of electron fluid oscillations in the wake gradually shrinking. Phase velocity of the wake promptly exceeds the vacuum speed of light, setting in near-forward emission of terahertz Cherenkov radiation. As the wake accelerates further, the Cherenkov emission ray rotates by 180∘. Emission from a given plasma locality is sustained for a finite interval of time, in the middle of which the wake experiences a ‘reversal,’ its phase velocity becoming singular and changing sign (Zhang C J et al 2017 Phys. Rev. Lett. 119 064801) At this instant, the electromagnetic energy flows at 90∘, the emission power reaching its peak. After the reversal, the wake keeps radiating into the rear hemisphere until its phase velocity becomes subluminal. Experimentally capturing evolution of the Cherenkov signal may thus shed light onto the plasma wake dynamics. Far away from the plasma, the radiation fills an expanding, almost spherical shell, the shell thickness increasing with an increase in the observation angle. The length of the terahertz signal sampled in the wave zone thus ranges from zero (forward emission) to a few tens of picoseconds (backward emission). The signal is positively chirped, its frequency increasing from the Langmuir frequency at the foot of the column to the Langmuir frequency at the top. Theoretical estimates for the regimes involving 10 TW-class drive pulses promise a few-kW emission power; the energy conversion efficiency, from optical to terahertz, of order 10−7; and an MV m−1-scale electric field strength centimeters away from the plasma.
Development of high-efficiency capacitive discharge using magnetic resonance wireless power transfer systems
Authors: Kim Ju Ho , Chung Chin-Wook 
Published: February 2021

Abstract
We developed a high-efficiency source in a capacitively coupled plasma using magnetic resonance wireless power transfer (MRWPT) systems, which has the advantage that the matcher efficiency is very high at low gas pressures (2 mTorr to 20 mTorr) and high density plasmas (about 1 × 1010 cm−3 to 5 × 1010 cm−3). At the non-resonance conditions, most of the RF power is dissipated by the transmitter coil and the plasma is not discharged. However, at the resonance condition, the plasma is discharged as the current flowing through the transmitter coil rapidly decreases, and the matcher efficiency is higher than 90% in all experiments. For analysis, the transformer model with MRWPT systems is developed. The experimental result is consistent with the model, and the results are discussed with the relevant physical mechanisms.