bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metal cation crosslinked, partially reduced graphene oxide membranes with enhanced stability for high salinity, produced water treatment by pervaporative separation
Authors: Almarzooqi Khalfan , Burton Nikolai D , Tsui Ting Y , Elkamel Ali , Pope Michael A 
Published: April 2024

Abstract
Graphene oxide (GO)-based membranes hold significant promise for applications ranging from energy storage to protective coatings, to saline water and produced water treatment, owing to their chemical stability and unique barrier properties achieving a high selectivity for water permeation. However, unmodified GO membranes are not stable when submerged in liquid water, creating challenges with their commercial utilization in aqueous filtration and pervaporation applications. To mitigate this, we develop an approach to modify GO membranes through a combination of low temperature thermal reduction and metal cation crosslinking. We demonstrate that Zn2+–rGO and Fe3+–rGO membranes had the highest permeation flux of 8.3 ± 1.5 l m−2 h−1 and 7.0 ± 0.4 l m−2 h−1, for saline water separation, respectively, when thermally reduced after metal cross-linking; These membranes maintained a high flux of 7.5 ± 0.7 l m−2 h−1, and 5.5 ± 0.3 l m−2 h−1 for produced water separation, respectively. All the membranes had a salt rejection higher than 99%. Fe3+ crosslinked membranes presented the highest organic solute rejections for produced water of 69%. Moreover, long term pervaporation testing was done for the Zn2+–rGO membrane for 12 h, and only a minor drop of 6% in permeation flux was observed, while Zn2+–GO had a drop of 24%. Both modifiers significantly enhanced the stability with Fe3+–rGO membranes displaying the highest mechanical abrasion resistance of 95% compared to non-reduced and non-crosslinked GO. Improved stability for all samples also led to higher selectivity to water over organic contaminants and only slightly reduced water flux across the membrane.
Measurement of specific heat by using non-isolating container and Arduino: a novel teaching method
Authors: Erol Mustafa , Kuzucu M Emre 
Published: April 2024

Abstract
This study reports a novel method to measure and teach the specific heat by means of ordinary non-isolating containers and Arduino microprocessors. The measurements are managed by simply placing cold substances in hot water and by monitoring the instant temperature variation via the Arduino UNO microprocessor. This method is original in the sense that it employs ordinary non-isolating containers and obvious heat loss from the container is determined by mathematically modelling the temperature decrease as a function of time. The specific heat measurements are managed based on the heat energy exchange between the hot water and the cold substance by extracting the heat loss to the environment. Proposed method is specifically employed for the substances of aluminium and copper and the measurements revealed that the relative errors of the measurements are 6.50% for copper and 1.38% for aluminium. This novel approach is very easy to implement, inexpensive and can effectively be employed on teaching physics, science and engineering. The novel method can also be employed on basic research activities and industrial applications.
Single-channel EOG sleep staging on a heterogeneous cohort of subjects with sleep disorders
Authors: van Gorp Hans , van Gilst Merel M , Overeem Sebastiaan , Dujardin Sylvie , Pijpers Angelique , van Wetten Bregje , Fonseca Pedro , van Sloun Ruud J G 
Published: April 2024

Abstract

Objective. Sleep staging based on full polysomnography is the gold standard in the diagnosis of many sleep disorders. It is however costly, complex, and obtrusive due to the use of multiple electrodes. Automatic sleep staging based on single-channel electro-oculography (EOG) is a promising alternative, requiring fewer electrodes which could be self-applied below the hairline. EOG sleep staging algorithms are however yet to be validated in clinical populations with sleep disorders. Approach. We utilized the SOMNIA dataset, comprising 774 recordings from subjects with various sleep disorders, including insomnia, sleep-disordered breathing, hypersomnolence, circadian rhythm disorders, parasomnias, and movement disorders. The recordings were divided into train (574), validation (100), and test (100) groups. We trained a neural network that integrated transformers within a U-Net backbone. This design facilitated learning of arbitrary-distance temporal relationships within and between the EOG and hypnogram. Main results. For 5-class sleep staging, we achieved median accuracies of 85.0% and 85.2% and Cohen’s kappas of 0.781 and 0.796 for left and right EOG, respectively. The performance using the right EOG was significantly better than using the left EOG, possibly because in the recommended AASM setup, this electrode is located closer to the scalp. The proposed model is robust to the presence of a variety of sleep disorders, displaying no significant difference in performance for subjects with a certain sleep disorder compared to those without. Significance. The results show that accurate sleep staging using single-channel EOG can be done reliably for subjects with a variety of sleep disorders.
Photovoltaic spatial gap solitons in biased photorefractive optical lattices
Authors: Katti Aavishkar , Umesh Draupath 
Published: April 2024

Abstract
We investigate the existence and characteristics of spatially confined optical gap solitons within an optical lattice embedded in a biased bulk photovoltaic photorefractive crystal. The Floquet-Bloch theory is used to analyze the uniform lattice and derive the optical lattice band structure. In the photonic band gaps, which are typically opaque to light transmission, the photorefractive nonlinearity permits the formation of solitons. The paraxial Helmholtz equation is set up and solved thereby discovering single hump and double hump soliton states in both band gaps. Interestingly, we have not found any multi peak solitons to exist in this particular case. We examine the characteristics of these gap solitons, finding that the soliton width (an indicator of nonlinearity) and intensity depend on their location within the band gap. We find that the magnitude of the external electric field profoundly affects the gap soliton characteristics. Additionally, the Vakhitov-Kolokolov (VK) criterion, perturbation analysis and numerical techniques are used to analyze the stability of the various types of the spatial gap solitons in both the band gaps.
Green lubricants in action: a comprehensive performance evaluation of groundnut oil-based cutting fluids in metal machining processes
Authors: Srinivas M Shanmuka , Kumar Dheeraj , Suvin P S , Kailas Satish V , Pawar Sanjay R , Roy Choudhury Mridusmita 
Published: April 2024

Abstract
As industries worldwide seek environmentally sustainable solutions, the metalworking sector faces a growing need for eco-friendly alternatives to traditional cutting fluids. This abstract introduces the concept of an innovative approach to cutting fluid technology—the use of groundnut oil as a base material for machining fluids. Derived from peanuts, groundnut oil presents a renewable and biodegradable alternative to petroleum-based counterparts, addressing concerns related to resource depletion and environmental impact. A comprehensive performance evaluation of groundnut oil- based cutting fluid has been carried out by series of critical tests such as separation testing, particle size and stability testing, frictional testing, corrosion testing and drilling testing. The results of these tests collectively contribute to a comprehensive understanding of groundnut oil-based cutting fluids, shedding light on their potential as sustainable and high-performance alternatives in metalworking. The zeta potential for the prepared green cutting fluid has been found to be 49.10 mV. The dimensions of the dispersed particles in a fluid of the cutting fluid have been found as 250–260 nm. The environmentally friendly cutting fluid exhibits favourable outcomes in corrosion resistance, frictional performance, and drilling efficacy during testing.
A modified lognormal approximation of the Lyman-α forest: comparison with full hydrodynamic simulations at 2 ≤ z ≤ 2.7
Authors: Arya B. , Roy Choudhury T. , Paranjape A. , Gaikwad P. 
Published: April 2024

Abstract
Observations of the Lyman-α forest in distant quasar spectra with upcoming surveys
are expected to provide significantly larger and higher-quality datasets. To interpret these
datasets, it is imperative to develop efficient simulations. One such approach is based on the
assumption that baryonic densities in the intergalactic medium (IGM) follow a lognormal
distribution. We extend our earlier work to assess the robustness of the lognormal model of the
Lyman-α forest in recovering the parameters characterizing IGM state, namely, the
mean-density IGM temperature (T
0), the slope of the temperature-density relation (γ),
and the hydrogen photoionization rate (Γ12), by comparing with high-resolution Sherwood
SPH simulations across the redshift range 2 ≤ z ≤ 2.7. These parameters are estimated
through a Markov Chain Monte Carlo (MCMC) technique, using the mean and power spectrum of the
transmitted flux. We find that the usual lognormal distribution of IGM densities cannot recover
the parameters of the SPH simulations. This limitation arises from the fact that the SPH baryonic
density distribution cannot be described by a simple lognormal form. To address this, we extend
the model by scaling the linear density contrast by a parameter ν. While the resulting
baryonic density is still lognormal, the additional parameter gives us extra freedom in setting
the variance of density fluctuations. With this extension, values of T
0 and γ implied in
the SPH simulations are recovered at ∼ 1 - σ (≲ 10%) of the median (best-fit)
values for most redshifts bins. However, this extended lognormal model cannot recover
Γ12 reliably, with the best-fit value discrepant by ≳ 3 - σ for z >
2.2. Despite this limitation in the recovery of Γ12, whose origins we explain, we argue
that the model remains useful for constraining cosmological parameters.
Covariance matrices for the Lyman-α forest using the lognormal approximation
Authors: Arya B. , Paranjape A. , Roy Choudhury T. 
Published: April 2024

Abstract
We investigate the nature of correlations in the small-scale flux statistics of the
Lyman-α (Lyα) forest across redshift bins. Understanding and characterising these
correlations is important for unbiased cosmological and astrophysical parameter inference using
the Lyα forest. We focus on the 1-dimensional flux power spectrum (FPS) and mean flux
(F̅) simulated using the semi-numerical lognormal model we developed in earlier work. The
lognormal model can capture the effects of long wavelength modes with relative ease as compared to
full smoothed particle hydrodynamical (SPH) simulations that are limited by box volume. For a
single redshift bin of size Δz ≃ 0.1, we show that the lognormal model predicts
positive cross-correlations between k-bins in the FPS, and a negative correlation for F̅ × FPS, in qualitative agreement with SPH simulations and theoretical expectations. For
measurements across two neighbouring redshift bins of width Δ z each (using long flux
skewers of length 2Δ z that are 'split' in half), the lognormal model predicts an
anti-correlation for FPS × FPS and a positive correlation for F̅ ×
FPS, caused by modes with the longest wavelengths. This is in contrast to SPH simulations which
predict a negligible magnitude for cross-redshift correlations derived from such `split' skewers,
and we discuss possible reasons for this difference. Finally, we perform a preliminary test of the
impact of neglecting long wavelength modes on parameter inference, finding that whereas the
correlation structure of neighbouring redshift bins has relatively little impact, the absence of
long wavelength modes in the model can lead to ≳ 2 - σ biases in the inference of
astrophysical parameters. Our results motivate a more careful treatment of long wavelength modes
in analyses that rely on the small-scale Lyα forest for parameter inference.
Splitting the spacetime: a systematic analysis of foliation dependence in cosmic averaging
Authors: Mourier Pierre , Heinesen Asta 
Published: April 2024

Abstract
It is a fundamental unsolved question in general relativity how to unambiguously characterize the effective collective dynamics of an ensemble of fluid elements sourcing the local geometry, in the absence of exact symmetries.
In a cosmological context this is sometimes referred to as the averaging problem.
At the heart of this problem in relativity is the non-uniqueness of the choice of foliation within which the statistical properties of the local spacetime are quantified,
which can lead to ambiguity in the formulated average theory. This has led to debate in the literature on how to best construct and view such a coarse-grained hydrodynamic theory.
Here, we address this ambiguity by performing the first quantitative investigation of foliation dependence in cosmological spatial averaging. Starting from the aim of constructing slicing-independent integral functionals (volume, mass, entropy, etc.) as well as average functionals (mean density, average curvature, etc.) defined on spatial volume sections, we investigate infinitesimal foliation variations and derive results on the foliation dependence of functionals and on extremal leaves.
Our results show that one may only identify fully foliation-independent integral functionals in special scenarios, requiring the existence of associated conserved currents.
We then derive bounds on the foliation dependence of integral functionals for general scalar quantities under finite variations within physically motivated classes of foliations.
Our findings provide tools that are useful for quantifying, eliminating or constraining the foliation dependence in cosmological averaging.
First-principles study on stability and superconductivity of ternary hydride LaYHx (x = 2, 3, 6 and 8)
Authors: Yan 颜 Xiao-Zhen 小珍 , Zhou 周 Xing-Zi 幸姿 , Liu 刘 Chao-Fei 超飞 , Xu 徐 Yin-Li 寅力 , Huang 黄 Yi-Bin 毅斌 , Sheng 盛 Xiao-Wei 晓伟 , Chen 陈 Yang-Mei 杨梅 
Published: April 2024

Abstract
Recent studies have shown that the La- and Y-hydrides can exhibit significant superconducting properties under high pressures. In this paper, we investigate the stability, electronic and superconducting properties of LaYH
x
(x = 2, 3, 6 and 8) under 0–200 GPa. It is found that LaYH2 stabilizes in the C2/m phase at ambient pressure, and transforms to the Pmmn phase at 67 GPa. LaYH3 stabilizes in the C2/m phase at ambient pressure, and undergoes phase transitions of C2/m → P21/m → R3m at 12 GPa and 87 GPa, respectively. LaYH6 stabilizes in the P43212 phase at ambient pressure, and undergoes phase transitions of P43212 → P4/mmm → Cmcm at 28 GPa and 79 GPa, respectively. LaYH8 stabilizes in the Imma phase at 60 GPa and transforms to the P4/mmm phase at 117 GPa. Calculations of the electronic band structures show that the P4/mmm-LaYH8 and all phases of LaYH2 and LaYH3 exhibit metallic character. For the metallic phases, we then study their superconducting properties. The calculated superconducting transition temperatures (T
c) are 0.47 K for C2/m-LaYH2 at 0 GPa, 0 K for C2/m-LaYH3 at 0 GPa, and 55.51 K for P4/mmm-LaYH8 at 50 GPa.
Magnetic and electrical transport properties in GdAlSi and SmAlGe
Authors: Gong 巩 Jing 静 , Wang 王 Huan 欢 , Ma 马 Xiao-Ping 小平 , Zeng 曾 Xiang-Yu 祥雨 , Lin 林 Jun-Fa 浚发 , Han 韩 Kun 坤 , Wang 王 Yi-Ting 乙婷 , Xia 夏 Tian-Long 天龙 
Published: April 2024

Abstract
We conduct a detailed examination of the magnetic and electrical transport properties in GdAlSi and SmAlGe crystals, which possess a LaPtSi-type structure (space group I41
md). The magnetic susceptibility data unambiguously reveal magnetic ordering below a characteristic transition temperature (T
N). For GdAlSi, a hysteresis loop is observed in the magnetization and magnetoresistance curves within the ab plane when the magnetic field is applied below T
N, which is around 32 K. Notable specific heat anomalies are detected at 32 K for GdAlSi and 6 K for SmAlGe, confirming the occurrence of magnetic transitions. In addition, the extracted magnetic entropy at high temperatures is consistent with the theoretical value of Rln(2J + 1) for J = 7/2 in Gd3+ and J = 5/2 in Sm3+, respectively. SmAlGe also exhibits Schottky-like specific heat contributions. Additionally, both GdAlSi and SmAlGe exhibit positive magnetoresistance and a normal Hall effect.
A Possible X-ray Quasi-periodic Oscillation in the Narrow-line Seyfert 1 Galaxy Mrk 142
Authors: Zhong Xiao-Gu , Wang Jian-Cheng , Chen Yong-Yun , Yu Xiao-Ling 
Published: April 2024

Abstract
A possible quasi-periodic oscillation (QPO) at frequency 7.045 × 10−5 Hz is found in the narrow-line Seyfert 1 galaxy Mrk 142 in the data of XMM-Newton collected on 2020 April 11. We find that the QPO signal is statistically significantly larger than the 5σ level and highly coherent with quality factor Q > 5 at the 0.3–10 keV band by using the method of the Lomb–Scargle Periodogram, the Weighted Wavelet Z-transform and the REDFIT. We analyze the data in 0.3–0.6 keV, 0.6–1 keV, 1–3 keV and 3–10 keV energy bands, and find obvious QPO signals at 0.3–0.6 keV and 1–3 keV bands. We then analyze the time-average spectra and time variability at the QPO frequency of 7.045 × 10−5 Hz, and use a model to fit them. We find that the QPO signal mainly comes from the X-ray hot corona.
Isochrone Fitting of Galactic Globular Clusters—VI. High-latitude Clusters NGC 5024 (M53), NGC 5053, NGC 5272 (M3), NGC 5466, and NGC 7099 (M30)
Authors: Gontcharov G. A. , Savchenko S. S. , Marchuk A. A. , Bonatto C. J. , Ryutina O. S. , Khovritchev M. Yu. , Il’in V. B. , Mosenkov A. V. , Poliakov D. M. , Smirnov A. A. 
Published: April 2024

Abstract
We fit various color–magnitude diagrams (CMDs) of the high-latitude Galactic globular clusters NGC 5024 (M53), NGC 5053, NGC 5272 (M3), NGC 5466, and NGC 7099 (M30) by isochrones from the Dartmouth Stellar Evolution Database and Bag of Stellar Tracks and Isochrones for α–enrichment [α/Fe] = +0.4. For the CMDs, we use data sets from Hubble Space Telescope, Gaia, and other sources utilizing, at least, 25 photometric filters for each cluster. We obtain the following characteristics with their statistical uncertainties for NGC 5024, NGC 5053, NGC 5272, NGC 5466, and NGC 7099, respectively: metallicities [Fe/H] = −1.93 ± 0.02, −2.08 ± 0.03, −1.60 ± 0.02, −1.95 ± 0.02, and −2.07 ± 0.04 dex with their systematic uncertainty 0.1 dex; ages 13.00 ± 0.11, 12.70 ± 0.11, 11.63 ± 0.07, 12.15 ± 0.11, and 12.80 ± 0.17 Gyr with their systematic uncertainty 0.8 Gyr; distances (systematic uncertainty added) 18.22 ± 0.06 ± 0.60, 16.99 ± 0.06 ± 0.56, 10.08 ± 0.04 ± 0.33, 15.59 ±0.03 ± 0.51, and 8.29 ± 0.03 ± 0.27 kpc; reddenings E(B − V) = 0.023 ± 0.004, 0.017 ± 0.004, 0.023 ± 0.004, 0.023 ± 0.003, and 0.045 ± 0.002 mag with their systematic uncertainty 0.01 mag; extinctions A
V = 0.08 ± 0.01, 0.06 ± 0.01, 0.08 ± 0.01, 0.08 ± 0.01, and 0.16 ± 0.01 mag with their systematic uncertainty 0.03 mag, which suggest the total Galactic extinction A
V = 0.08 across the whole Galactic dust to extragalactic objects at the North Galactic Pole. The horizontal branch morphology difference of these clusters is explained by their different metallicity, age, mass-loss efficiency, and loss of low-mass members in the evolution of the core-collapse cluster NGC 7099 and loose clusters NGC 5053 and NGC 5466.
Multi-timescale neuromodulation strategy for closed-loop deep brain stimulation in Parkinson’s disease
Authors: Quan Zhaoyu , Li Yan , Wang Shouyan 
Published: April 2024

Abstract

Objective. Beta triggered closed–loop deep brain stimulation (DBS) shows great potential for improving the efficacy while reducing side effect for Parkinson’s disease. However, there remain great challenges due to the dynamics and stochasticity of neural activities. In this study, we aimed to tune the amplitude of beta oscillations with different time scales taking into account influence of inherent variations in the basal ganglia–thalamus–cortical circuit. Approach. A dynamic basal ganglia–thalamus–cortical mean–field model was established to emulate the medication rhythm. Then, a dynamic target model was designed to embody the multi-timescale dynamic of beta power with milliseconds, seconds and minutes. Moreover, we proposed a closed-loop DBS strategy based on a proportional–integral–differential (PID) controller with the dynamic control target. In addition, the bounds of stimulation amplitude increments and different parameters of the dynamic target were considered to meet the clinical constraints. The performance of the proposed closed-loop strategy, including beta power modulation accuracy, mean stimulation amplitude, and stimulation variation were calculated to determine the PID parameters and evaluate neuromodulation performance in the computational dynamic mean–field model. Main results. The Results show that the dynamic basal ganglia–thalamus–cortical mean–field model simulated the medication rhythm with the fasted and the slowest rate. The dynamic control target reflected the temporal variation in beta power from milliseconds to minutes. With the proposed closed-loop strategy, the beta power tracked the dynamic target with a smoother stimulation sequence compared with closed-loop DBS with the constant target. Furthermore, the beta power could be modulated to track the control target under different long-term targets, modulation strengths, and bounds of the stimulation increment. Significance. This work provides a new method of closed–loop DBS for multi-timescale beta power modulation with clinical constraints.
A lateralized motor network in order to understand adaptation to visuomotor rotation
Authors: Elango Sundari , Chakravarthy V Srinivasa , Mutha Pratik K 
Published: April 2024

Abstract

Objective. The functional asymmetry between the two brain hemispheres in language and spatial processing is well documented. However, a description of difference in control between the two hemispheres in motor function is not well established. Our primary objective in this study was to examine the distribution of control in the motor hierarchy and its variation across hemispheres. Approach. We developed a computation model termed the bilateral control network and implemented the same in a neural network framework to be used to replicate certain experimental results. The network consists of a simple arm model capable of making movements in 2D space and a motor hierarchy with separate elements coding target location, estimated position of arm, direction, and distance to be moved by the arm, and the motor command sent to the arm. The main assumption made here is the division of direction and distance coding between the two hemispheres with distance coded in the non-dominant and direction coded in the dominant hemisphere. Main results. With this assumption, the network was able to show main results observed in visuomotor adaptation studies. Importantly it showed decrease in error exhibited by the untrained arm while the other arm underwent training compared to the corresponding naïve arm’s performance—transfer of motor learning from trained to the untrained arm. It also showed how this varied depending on the performance variable used—with distance as the measure, the non-dominant arm showed transfer and with direction, dominant arm showed transfer. Significance. Our results indicate the possibility of shared control between the two hemispheres. If indeed found true, this result could have major significance in motor rehabilitation as treatment strategies will need to be designed in order to account for this and can no longer be confined to the arm contralateral to the affected hemisphere.