bluuebunny/crossref_metadata_2025 huggingface dataset:
Changing Tocolytic Exposures among Neonatal Intensive Care Unit Admitted Preterm Infants
Authors: Jarman Meghan L. , Bennett Monica M. , Louis Judette M. , Clark Reese H. , Tolia Veeral N. , Ahmad Kaashif A.
Published: January 2022

Objective Since 2010, the American College of Obstetrics and Gynecology have released three committee opinions to recommend and reaffirm the utility of magnesium sulfate for neuroprotection and later for tocolysis to achieve antenatal steroid course completion in preterm labor. We sought to determine changes in antenatal magnesium sulfate exposure and other tocolytic agents for pregnancies resulting in neonatal intensive care unit (NICU)-admitted preterm infants.

Study Design Using the Pediatrix Clinical Data Warehouse, we evaluated all inborn infants delivered between 22 and 33 weeks' gestation and admitted to the intensive care units from 2009 to 2018. We classified patients based on antenatal exposure to tocolytic medications: calcium channel blockers (nifedipine and amlodipine), betamimetics (terbutaline, theophylline, and ritodrine), prostaglandin inhibitors (indomethacin), and magnesium sulfate.

Results A total of 229,781 patients met inclusion criteria. During the study period, magnesium sulfate exposure increased from 27.6 to 57.7% of births while betamimetic exposure decreased from 10.2 to 5.2%. Increasing magnesium sulfate exposure over time was seen at all gestational ages examined and magnesium exposure was most common between 23 and 31 weeks' gestation. By 2017 to 2018, 70.5% of 24 to 29 weeks' gestation NICU infants received exposure to at least one tocolytic agent while this remained at 53.7% of 32 to 33 weeks' NICU admitted infants. Antenatal steroid exposure increased from 74.8 to 87.4% during the study period.

Conclusion For NICU-admitted preterm infants, prenatal exposure patterns to tocolytic agents has shifted since 2009 with prenatal magnesium sulfate exposure increasing significantly. Antenatal steroid exposure has risen concurrently. Exposure to tocolytic agents is the highest among preterm infants born between 24 and 29 weeks' gestation.

Key Points
Spatial stratification and socio-spatial inequalities: the case of Seoul and Busan in South Korea
Authors: Han Seungwoo
Published: January 2022

This study approaches the spatial stratification phenomenon through a data-based social stratification approach. In addition, by applying a dissimilarity-based clustering algorithm, this study analyzes how regions cluster as well as their disparities, thereby analyzing socio-spatial inequalities. Ultimately, through map visualization, this study seeks to visually identify spatial forms of social inequality and gain insight into the social structure for policy implications. The results determine how the regions are socioeconomically structured and identify the social inequalities between the spaces.
Highlighting versatile contrast agents for high-field MRI
Authors: Johnson-Groh Mara
Published: January 2022

Novel contrast agents for high-field MRI could simultaneously improve imaging and drug delivery.
The role of pre-existing heterogeneities in materials under shock and spall
Authors: Flanagan R. M. , Fensin S. J. , Meyers M. A.
Published: January 2022

There has been a challenge for many decades to understand how heterogeneities influence the behavior of materials under shock loading, eventually leading to spall formation and failure. Experimental, analytical, and computational techniques have matured to the point where systematic studies of materials with complex microstructures under shock loading and the associated failure mechanisms are feasible. This is enabled by more accurate diagnostics as well as characterization methods. As interest in complex materials grows, understanding and predicting the role of heterogeneities in determining the dynamic behavior becomes crucial. Early computational studies, hydrocodes, in particular, historically preclude any irregularities in the form of defects and impurities in the material microstructure for the sake of simplification and to retain the hydrodynamic conservation equations. Contemporary computational methods, notably molecular dynamics simulations, can overcome this limitation by incorporating inhomogeneities albeit at a much lower length and time scale. This review discusses literature that has focused on investigating the role of various imperfections in the shock and spall behavior, emphasizing mainly heterogeneities such as second-phase particles, inclusions, and voids under both shock compression and release. Pre-existing defects are found in most engineering materials, ranging from thermodynamically necessary vacancies, to interstitial and dislocation, to microstructural features such as inclusions, second phase particles, voids, grain boundaries, and triple junctions. This literature review explores the interaction of these heterogeneities under shock loading during compression and release. Systematic characterization of material heterogeneities before and after shock loading, along with direct measurements of Hugoniot elastic limit and spall strength, allows for more generalized theories to be formulated. Continuous improvement toward time-resolved, in situ experimental data strengthens the ability to elucidate upon results gathered from simulations and analytical models, thus improving the overall ability to understand and predict how materials behave under dynamic loading.
Microsphere-assisted microscopy
Authors: Darafsheh Arash
Published: January 2022

Light microscopy is one of the most powerful techniques for nondestructive real-time imaging of specimens at a resolution beyond the reach of human eyes. However, the spatial resolution of any conventional microscope is fundamentally limited by the diffraction of light waves at the lens aperture. Microsphere-assisted microscopy (MAM) has emerged in the past decade as an interestingly simple yet efficient method to improve imaging resolution. In MAM, a micrometer-scale dielectric sphere is placed in the immediate vicinity of the specimen to enhance the imaging resolution and magnification. MAM is highly versatile and can be combined with various systems including wide-field, confocal, and fluorescent microscopes to name a few. The exact resolution enhancement mechanism in MAM is not yet clearly understood and is under intense investigation; however, fundamentally, it can be linked to the increase in the system's effective numerical aperture and evanescence wave collection, and possibly to contributions from photonic nanojet effect, resonance, and coherent effects. Various claims have been made in the literature about the resolution gain in MAM, most of which are due to using arbitrary criteria for quantifying the resolution and possible contributions from specimen-specific parameters in imaging metallic nanostructures. In this Tutorial, we discuss the progress in MAM with special scrutiny of the imaging resolution.
On the multiplicity and concentration of positive solutions to a Kirchhoff-type problem with competing potentials
Authors: Fan Haining , Liu Xiaochun
Published: January 2022

We study the multiplicity and concentration of positive solutions for a Kirchhoff-type problem involving competing weight potentials and the nonlinearity K(x)|u|p−2u(2 < p < 4) in R3. Such a problem cannot be studied by applying variational methods in a standard way, even by restricting its corresponding energy functional on the Nehari manifold, because (PS) sequence may not be bounded. In this paper, by the decomposition of the Nehari manifold and Ljusternik–Schnirelmann category, we relate the number of positive solutions to the category of the global minima set of a suitable ground energy function. This is perhaps the first work of studying such problems via the Ljusternik–Schnirelmann category. An interesting point is that unlike some methods that work only for the case of R3 {see the work of G. Li and H. Ye [J. Differ. Equations 257, 566–600 (2014)] and Liu et al. [J. Differ. Equations 266, 5912–5941 (2019)]}, our method is also applicable for the bounded domain case.
Total angular momentum representation for state-to-state quantum scattering of cold molecules in a magnetic field
Authors: Koyu Suyesh , Hermsmeier Rebekah , Tscherbul Timur V.
Published: January 2022

We show that the integral cross sections for state-to-state quantum scattering of cold molecules in a magnetic field can be efficiently computed using the total angular momentum representation despite the presence of unphysical Zeeman states in the eigenspectrum of the asymptotic Hamiltonian. We demonstrate that the unphysical states arise due to the incompleteness of the space-fixed total angular momentum basis caused by using a fixed cutoff value Jmax for the total angular momentum of the collision complex J. As a result, certain orbital angular momentum (l) basis states lack the full range of J values required by the angular momentum addition rules, resulting in the appearance of unphysical states. We find that by augmenting the basis with a full range of J-states for every l, it is possible to completely eliminate the unphysical states from quantum scattering calculations on molecular collisions in external magnetic fields. To illustrate the procedure, we use the augmented basis sets to calculate the state-to-state cross sections for rotational and spin relaxation in cold collisions of 40CaH(X2Σ+, v = 0, N = 1, MN = 1, MS = 1/2) molecules with 4He atoms in a magnetic field. We find excellent agreement with benchmark calculations, validating our proposed procedure. We find that N-conserving spin relaxation from the highest-energy to the lowest-energy Zeeman state of the N = 1 manifold, |1112〉→|1−1−12〉 is nearly completely suppressed due to the lack of spin–rotation coupling between the fully spin-stretched Zeeman states. Our results demonstrate the possibility of rigorous, computationally efficient, and unphysical state-free quantum calculations on cold molecular collisions and on near-threshold energy levels of strongly anisotropic atom-molecule collision complexes in an external magnetic field.
Hydrogen in single-crystalline anatase TiO2
Authors: Lavrov E. V. , Chaplygin I. , Herklotz F. , Melnikov V. V. , Kutin Y.
Published: January 2022

Titanium dioxide (TiO2, also known as titania) has attracted a great deal of attention since the discovery of photocatalytic splitting of water under ultraviolet light exposure by Fujishima and Honda. Three modifications of TiO2 are known to occur in nature: rutile, brookite, and anatase, of which only the first is a stable polymorph of bulk titania. The contribution of the surface free energy, however, makes anatase a stable polymorph at the nanometer scale. Compared to rutile, anatase has a longer carrier lifetime and exciton diffusion length, higher electron mobility, and is an order of magnitude more efficient in photocatalysis, which makes it a material of choice for a variety of applications. Hydrogen is a common impurity in TiO2 with a strong impact on its electrical and optical properties. In this Perspective, we discuss the application of IR absorption, Raman scattering, electron paramagnetic resonance, and ab initio theory to get insight into the properties of hydrogen in bulk single-crystalline anatase. In particular, interstitial hydrogen, hydrogen substituting for oxygen, the nature of “hidden” species, as well as complexes formed by hydrogen with acceptors are considered.
Enhanced tunnel magnetoresistance in Fe/Mg4Al-Ox/Fe(001) magnetic tunnel junctions
Authors: Scheike Thomas , Wen Zhenchao , Sukegawa Hiroaki , Mitani Seiji
Published: January 2022

Spinel MgAl2O4 and family oxides are emerging barrier materials useful for magnetic tunnel junctions (MTJs). We report large tunnel magnetoresistance (TMR) ratios up to 429% at room temperature (RT) and 1034% at 10 K in a Fe/Mg-rich spinel/Fe(001) MTJ prepared using electron-beam evaporation of Mg4Al-Ox. Resistance oscillations with a MTJ barrier thickness of 0.3 nm were significantly enhanced compared to those of a Fe/MgO/Fe(001) MTJ, resulting in a large TMR oscillation peak-to-valley difference of 125% at RT. The differential conductance (dI/dV) spectra were symmetric with bias polarity, and the spectrum in the parallel magnetization state at low temperature demonstrates significant peaks within broad local minima at |V| = 0.2–0.6 V, indicating improved barrier interfaces by the Mg4Al-Ox barrier. This study demonstrates that TMR ratios in Fe(001)-MTJs can still be improved.
Quantifying the effectiveness of betaherpesvirus-vectored transmissible vaccines
Authors: Varrelman Tanner J. , Remien Christopher H. , Basinski Andrew J. , Gorman Shelley , Redwood Alec , Nuismer Scott L.
Published: January 2022

Significance

Spillover of infectious diseases from wildlife populations into humans is an increasing threat to human health and welfare. Current approaches to manage these emerging infectious diseases are largely reactive, leading to deadly and costly time lags between emergence and control. Here, we use mathematical models and data from previously published experimental and field studies to evaluate the scope for a more proactive approach based on transmissible vaccines that eliminates pathogens from wild animal populations before spillover can occur. Our models are focused on transmissible vaccines designed using herpes virus vectors and demonstrate that these vaccines—currently under development for several important human pathogens—may have the potential to rapidly control zoonotic pathogens within the reservoir hosts.
Probing molecular crowding in compressed tissues with Brillouin light scattering
Authors: Yan Guqi , Monnier Sylvain , Mouelhi Malèke , Dehoux Thomas
Published: January 2022

Significance

Volume regulation is key in maintaining important tissue functions, such as growth or healing. In this process, the role of efflux of cellular fluids is difficult to capture due to the lack of apt technologies. Here, we use a tool based on Brillouin light scattering (BLS) that uses the interaction of a laser light with inherent picosecond timescale density fluctuations in the sample. We induced gradual volume decrease in multicellular spheroids using osmotic perturbations. BLS revealed a nonlinear increase of the tissue compressibility due to the subsequent increased biopolymer crowding within the cells. Our findings should inspire research regarding volume regulation and cellular crowding in tissues and stimulate the emergence of models for cell mechanics at short timescales.
NO rapidly mobilizes cellular heme to trigger assembly of its own receptor
Authors: Dai Yue , Faul Emily M. , Ghosh Arnab , Stuehr Dennis J.
Published: January 2022

Significance

Nitric oxide (NO) performs many biological functions, but how it operates at the molecular and cellular levels is not fully understood. We discovered that cell NO generation at physiologic levels triggers a rapid redeployment of intracellular heme, an iron-containing cofactor, and we show that this drives the assembly of the natural NO receptor protein, soluble guanylyl cyclase, which is needed for NO to perform its biological signaling functions. Our study uncovers a way that NO can shape biological signaling processes and a way that cells may use NO to control their hemeprotein activities through deployment of the heme cofactor. These concepts broaden our understanding of NO function in biology and medicine.
Aluminum Cayley trees as scalable, broadband, multiresonant optical antennas
Authors: Simon Thomas , Li Xiaoyan , Martin Jérôme , Khlopin Dmitry , Stéphan Odile , Kociak Mathieu , Gérard Davy
Published: January 2022

Significance

Optical antennas perform the same functions for light that aerials do for radio waves; they can extract energy from a propagating electromagnetic field, and they can convert localized energy into propagating radiation. Here, we use a fractal-like design, the Cayley tree, to create optical antennas. Implementing this simple iterative design with aluminum as the antenna material, we demonstrate optical antennas with broadband operating range from energies corresponding to thermal radiation up to ultraviolet. The spatial distribution of electromagnetic energy inside the antennas is experimentally imaged using electron energy loss spectroscopy, a technique allowing direct imaging and spectroscopy at the nanoscale. Such antennas are interesting for applications including photodetection, nonlinear frequency conversion, and infrared absorption spectroscopy.
Injectable amnion hydrogel-mediated delivery of adipose-derived stem cells for osteoarthritis treatment
Authors: Bhattacharjee Maumita , Escobar Ivirico Jorge L. , Kan Ho-Man , Shah Shiv , Otsuka Takayoshi , Bordett Rosalie , Barajaa Mohammed , Nagiah Naveen , Pandey Rishikesh , Nair Lakshmi S. , Laurencin Cato T.
Published: January 2022

Significance

Osteoarthritis (OA) is a chronic disease affecting millions of people worldwide with no curative solution. In the present study, we developed a minimally invasive injectable system using amnion membrane (AM) from the human placenta as a carrier for fat tissue-derived stem cells (adipose-derived stem cells [ADSCs]) to treat OA. Both AM and ADSCs are rich sources of bioactive molecules that can target the sites of inflammation and reduce the inflammation-driven articular cartilage damage. Our study demonstrated the disease-modifying and regenerative potential of AM hydrogel, a comparable regenerative and disease-modifying effect of AM hydrogel and ADSCs, and the synergistic effect of AM with ADSCs in regenerating cartilage and attenuating OA.
Native and nonnative authors in L2 pronunciation
Authors: Levis John M.
Published: January 2022

Achieving nativeness in L2 pronunciation is not critical, nor is it critical for writing about L2 pronunciation. Using the experience of an L2 writer whose paper was rejected because of nonnative written features, this paper argues that it is past time for editors and reviewers to reject nativelike writing as a criterion for acceptance or rejection of an otherwise well-constructed contribution to research.
Social actors in the Singaporean LL
Authors: Tsiola Anna
Published: January 2022

This paper examines the uptake and interpretation of the Linguistic Landscape of Singapore by members of the community. The main goal is to explore Singaporeans’ ideologies pertaining to the languages depicted in the LL, as these ideologies instantiate themselves through interview discourses focusing on the signs. More specifically, participants’ ideologies emerge through the indexicalities they assign to the various languages and semiotic signs depicted in the LL, indexicalities such as globalness, localness, and prestige.
Experimental dielectronic recombination rate coefficients for lithium-like 40Ca17+
Authors: Khan Nadir , Huang Zhong-Kui , Wen Wei-Qiang , Wang Shu-Xing , Chen Chong-Yang , Zhang Chun-Yu , Wang Han-Bing , Liu Xin , Ma Wan-Lu , Chen Dong-Yang , Yao Ke , Zhao Dong-Mei , Mao Li-Jun , Ma Xiao-Ming , Li Jie , Tang Mei-Tang , Yin Da-Yu , Yuan You-Jin , Yang Jian-Cheng , Zhu Lin-Fan , Ma Xin-Wen
Published: January 2022

The rate coefficients for dielectronic recombination (DR) of lithium-like 40Ca17+ ions with ∆n = 0 core excitations are derived from electron–ion recombination spectra measured with merged-beams method at the heavy-ion storage ring CSRm. The experimental DR spectrum, in the electron–ion collision energy range of 0 to 42 eV in the center-of-mass frame, comprises of all DR resonance peaks belong to the 2s
2
S
1/2 → 2p
2
P
1/2, 3/2 core excitations. The resonant energies and strengths for the resolved resonances in 2pjnl series are determined by fitting of the measured DR peaks. The further interpretation of the measured DR rate coefficients has been performed by calculating the DR rate coefficients with relativistic configuration-interaction method implemented in flexible atomic code (FAC) and compared with the experimental results. The experimental results and FAC calculations are found to be in a good agreement within the experimental uncertainties. Moreover, temperature dependent plasma rate coefficients were constructed from 4 × 103 to 1 × 107 K energy region by convoluting experimental and theoretical DR rate coefficients with the Maxwellian energy distribution function and then compared with previously available data. The plasma DR rate coefficient is found to be significantly underestimated by the early theoretical data calculated by Jacobs et al, and Mazotta et al in the low temperature. In contrast, a very good agreement has been found between the theoretical DR data of Gu and Colgan et al and the presently measured results at the low temperature region. Therefore, the results in this work composed of a bench-mark data set for plasma modeling at the photoionized temperature range. We have also provided a fit to our measured and theoretical plasma rate coefficients for low temperature plasma modeling.
Chemical vapor deposited WS2/MoS2 heterostructure photodetector with enhanced photoresponsivity
Authors: Zhang Yudong , Chen Yukun , Qian Min , Xie Haifen , Mu Haichuan
Published: January 2022

Two-dimensional transition metal dichalcogenides (TMDCs) have attracted great interest due to their unique semiconductor properties. Among all TMDC materials, MoS2 and WS2 are promising for composing heterostructures. However, traditional TMDC heterostructure fabrication depends on transfer process, with drawbacks of interface impurity and small size. In this work, a two-step chemical vapor deposition (CVD) process was applied to synthesize large-scale WS2/MoS2 heterostructure. Surface morphology and crystal structure characterizations demonstrate the high-quality WS2/MoS2 heterostructure. The WS2/MoS2 heterostructure photodetector fabricated by photolithography exhibits an enhanced photoresponsivity up to 370 A W−1 in comparison with single WS2 or MoS2 devices. This study suggests a direct CVD growth of large-scale TMDC heterostructure films with clean interface. The built-in electric field at interface contributes to the separation of photo-generated electron–hole pairs, leading to enhanced photocurrent and responsivity, and showing promising potentials in photo-electric applications.
Radiation electron trajectory modulated DC surface flashover of polyimide in vacuum
Authors: Wang Xiaoping , Zheng Shusai , Li Zhen , Pan Shaoming , Fan Weibo , Min Daomin , Li Shengtao
Published: January 2022

Improving surface flashover voltage on vacuum-dielectric interface irradiated by electrons is a long-standing challenge for developing high-voltage and high-power spacecraft technology. The basic issue is understanding the role of radiation electrons in the process of surface flashover. In this paper, a ‘three-segment’ curve concerning the surface flashover properties under electron irradiation is discovered experimentally. As the gap distance of electrodes increase, the surface flashover voltage of polyimide during electron irradiation presents a trend of firstly increasing, then decreasing, and finally stabilizing. According to the simulation of the trajectory distribution for kinetic electrons, this trend is found to correspond with three typical stages respectively. In stage A, the kinetic electrons are completely deflected and the varying electrode parameters mainly affect the electric field distribution. In stage B, the kinetic electrons can irradiate the part of polyimide. The promoting effect of those electrons on flashover process enhance with the enlargement of the irradiated region. In stage C, trajectories are no longer seriously deflected and the role of kinetic electrons do not vary with electrode parameters. Combining with the results above, a model with combined effects of both kinetic and deposited electrons on surface flashover in vacuum is thus proposed, base on which the guidance for the methods of improving surface flashover voltage during electron irradiation is provided.
Investigation of anisotropic mechanical, electronic, and charge carrier transport properties of germanium-pnictogen monolayers
Authors: Abboud M , Ozbey D H , Kilic M E , Durgun E
Published: January 2022

Recently, novel two-dimensional (2D) GeP and GeAs systems have been fabricated by mechanical exfoliation and utilized in various applications. These developments have brought the 2D germanium-pnictogens, C2/m-GeX (X = N, P, As, Sb, and Bi) structures into the limelight. In this study, we systematically investigate the structural, mechanical, electronic, and charge carrier transport properties of GeX monolayers by using first-principles methods. Our results show that the considered systems are dynamically stable and possess anisotropic physical properties. Examined structures are found to be flexible, and their mechanical strength and stiffness decrease down the group-V, in line with the trends of the bond strength, cohesive energy, charge transfer, and electron localization function. Additionally, the zigzag in-plane direction is mechanically superior to the armchair direction. The electronic band structure calculations based on HSE06 hybrid functional with the inclusion of spin–orbit coupling indicate that GeX monolayers are either direct or quasi-direct semiconductors with band gaps lying within the infrared and visible spectrum. The estimated charge carrier mobilities are highly anisotropic and also differ significantly depending on the structure and carrier type. These unique properties render GeX monolayers as suitable 2D materials for flexible nanoelectronic applications.
Non-equilibrium thermoelectric transport across normal metal–quantum dot–superconductor hybrid system within the Coulomb blockade regime
Authors: Verma Sachin , Singh Ajay
Published: January 2022

A detailed investigation of the non-equilibrium steady-state electric and thermoelectric transport properties of a quantum dot (QD) coupled to the normal metallic and s-wave superconducting reservoirs (N–QD–S) are provided within the Coulomb blockade regime. Using non-equilibrium Keldysh Green’s function formalism, initially, various model parameter dependences of thermoelectric transport properties are analysed within the linear response regime. It is observed that the single-particle tunnelling close to the superconducting gap edge can generate a relatively large thermopower and figure of merit. Moreover, the Andreev tunnelling plays a significant role in the suppression of thermopower and figure of merit within the gap region. Further, within the non-linear regime, we discuss two different situations, i.e., the finite voltage biasing between isothermal reservoirs and the finite thermal gradient in the context of thermoelectric heat engine. In the former case, it is shown that the sub-gap Andreev heat current can become finite beyond the linear response regime and play a vital role in asymmetric heat dissipation and thermal rectification effect for low voltage biasing. The rectification of heat current is enhanced for strong on-dot Coulomb interaction and at low background thermal energy. In the latter case, we study the variation of thermovoltage, thermopower, maximum power output, and corresponding efficiency with the applied thermal gradient. These results illustrate that hybrid superconductor–QD nanostructures are promising candidates for the low-temperature thermal applications.
On the role of density fluctuations in the core turbulent transport of Wendelstein 7-X
Authors: Carralero D , Estrada T , Maragkoudakis E , Windisch T , Alonso J A , Velasco J L , Ford O , Jakubowski M , Lazerson S , Beurskens M , Bozhenkov S , Calvo I , Damm H , Fuchert G , García-Regaña J M , Höfel U , Marushchenko N , Pablant N , Sánchez E , Smith H M , Pasch E , Stange T
Published: January 2022

A recent characterization of core turbulence carried out with a Doppler reflectometer in the optimized stellarator Wendelstein 7-X (W7-X) found that discharges achieving high ion temperatures at the core featured an ITG-like suppression of density fluctuations driven by a reduction of the gradient ratio

η
i

=

L
n

/

L

T
i

(Carralero et al 2021 Nucl. Fusion
61 096015). In order to confirm the role of ITG turbulence in this process, we set out to establish experimentally the relation between core density fluctuations, turbulent heat flux and global confinement. With this aim, we consider the scenarios found in the previous work and carry out power balance analysis for a number of representative ones, including some featuring high ion temperature. We also evaluate the global energy confinement time and discuss it in the context of the ISS04 inter-stellarator scaling. We find that when turbulence is suppressed as a result of a reduction of η

i
, there is a reduction of ion turbulent transport, and global performance is improved as a result. This is consistent with ITG turbulence limiting the ion temperature at the core of W7-X. In contrast, when turbulence is reduced following a decrease in collisionality, no changes are observed in transport or confinement. This could be explained by ITG modes being combined with TEM turbulence when the latter is destabilized at low collisionalities.
Benchmark experiments of the power law parametrization of the effective ion collecting area of a planar Langmuir probe in low temperature plasmas
Authors: Lim Yegeon , Severn Greg , Yip Chi-Shung , Ghim Y-c
Published: January 2022

For unmagnetized low temperature Ar plasmas with plasma density ranging from 3 × 108 to 1010 cm−3 and an electron temperature of ∼1 eV, the expansion of the ion collecting area of a double-sided planar Langmuir probe with respect to probe bias is experimentally investigated, through a systematic scan of plasma parameters. In accordance with many existing numerical studies, the ion collecting area is found to follow a power law for a sufficiently negative probe bias. Within our experimental conditions, the power law coefficient and exponent have been parameterized as a function of the normalized probe radius and compared with numerical results where qualitatively comparable features are identified. However, numerical results underestimate the power law coefficient while the exponent is overestimated. Our experimental measurements also confirm that ion–neutral collisions play a role in determining the expanded ion collecting area, thus changing values of the power law coefficient and exponent. This work suggests that a power law fit to the ion collecting area must be performed solely based on experimentally obtained data rather than using empirical formulae from simulation results since material and cleanness of the probe, type of working gas, and neutral pressure may also affect the expansion of the ion collecting area, factors which are difficult to model in a numerical simulation. A proper scheme of analyzing an I–V characteristic of a Langmuir probe based on a power law fit is also presented.
Synthesis, structural, optical, and electrical properties of continuous wave and pulse laser sintered semiconductor Ge films
Authors: Islam Md Toriqul , Gupta Mool C
Published: January 2022

The crystallization process of Ge films by a continuous wave (CW) and a pulsed laser is very effective for producing smooth, homogeneous, and crack-free polycrystalline films to use in transistors, photodetectors, and photovoltaic applications. However, little progress has been made to directly crystallize Ge films based on micro/nanoparticles (NPs) using the laser sintering (LS) process. In this paper, a simultaneous LS and crystallization process of Ge micro/NPs to develop thick polycrystalline films on silicon substrates is demonstrated. Silicon substrates with a SiO2 insulating layer on top were considered for compatibility with complementary metal–oxide–semiconductor (CMOS) technology. The LS process was applied to solution deposited micro/NPs, 5 µm thick Ge films using both CW mode (infrared laser of wavelength 1070 nm) and pulse mode (UV laser of wavelength 355 nm) laser. After the LS process, around 2–2.5 µm thick film of polycrystalline Ge (pc-Ge) was achieved with optical and electrical properties comparable to traditionally developed chemical vapor deposited films. The crystallinity of the pc-Ge films was evaluated by Raman spectroscopy and x-ray diffraction (XRD). The laser-sintered films exhibited a Raman peak at 300 cm−1 and XRD 2θ peak at 27.35, which indicated the poly-crystalline structure. The fabricated film showed high hole mobility of 203 cm2 V−1 s−1, without any doping and film electrical resistivity value of 6.24 × 105 Ω-cm. The developed LS process allows the quick deposition of polycrystalline thick films, removing surface porosity and voids, increasing films adhesion with the substrate, and faster thermal annealing.
SuperMind: a survey of the potential of superconducting electronics for neuromorphic computing
Authors: Schneider Michael , Toomey Emily , Rowlands Graham , Shainline Jeff , Tschirhart Paul , Segall Ken
Published: January 2022

Neuromorphic computing is a broad field that uses biological inspiration to address computing design. It is being pursued in many hardware technologies, both novel and conventional. We discuss the use of superconductive electronics for neuromorphic computing and why they are a compelling technology for the design of neuromorphic computing systems. One example is the natural spiking behavior of Josephson junctions and the ability to transmit short voltage spikes without the resistive capacitive time constants that typically hinder spike-based computing. We review the work that has been done on biologically inspired superconductive devices, circuits, and architectures and discuss the scaling potential of these demonstrations.
Analytic correlation of inflationary potential to power spectrum shape: limits of validity, and `no-go' for small field model analytics
Authors: Wolfson Ira
Published: January 2022

The primordial power spectrum informs the possible inflationary histories of our universe. Given a power spectrum, the ensuing cosmic microwave background is calculated and compared to the observed one. Thus, one focus of modern cosmology is building well-motivated inflationary models that predict the primordial power spectrum observables. The common practice uses analytic terms for the scalar spectral index ns and the index running α, forgoing the effort required to evaluate the model numerically. However, the validity of these terms has never been rigorously probed and relies on perturbative methods, which may lose their efficacy for large perturbations. The requirement for more accurate theoretical predictions becomes crucial with the advent of highly sensitive measuring instruments. This paper probes the limits of the perturbative treatment that connects inflationary potential parameters to primordial power spectrum observables. We show that the validity of analytic approximations of the scalar index roughly respects the large-field/small-field dichotomy. We supply an easily calculated measure for relative perturbation amplitude and show that, for large field models, the validity of analytical terms extends to ∼ 3% perturbation relative to a power-law inflation model.
Conversely, the analytical treatment loses its validity for small field models with as little as 0.1% perturbation relative to the small-field test-case. By employing the most general artificial neural networks and multinomial functions up to the twentieth degree and demonstrating their shortcomings, we show that no reasonable and universal analytic expressions correlating small field models to the observables they yield exists.
Finally, we discuss the possible implications of this work and supply the validity heuristic for large and small field models.
Spin–orbit stable dirac nodal line in monolayer B6O
Authors: Liu Wen-Rong , Zhang Liang , Dong Xiao-Jing , Ji Wei-Xiao , Wang Pei-Ji , Zhang Chang-Wen
Published: January 2022

The two-dimensional (2D) materials with nodal line band crossing have been attracting great research interest. However, it remains a challenge to find high-stable nodal line structure in 2D systems. Herein, based on the first-principles calculations and theoretical analysis, we propose that monolayer B6O possesses symmetry protected Dirac nodal line (DNL) state, with its Fermi velocity of 106 m/s in the same order of magnitude as that of graphene. The origin of DNL fermions is induced by coexistence of time-reversal symmetry and inversion symmetry. A two-band tight-binding model is further given to understand the mechanism of DNL. Considering its robustness against spin–orbit coupling (SOC) and high structural stability, these results suggest monolayer B6O as a new platform for realizing future high-speed low-dissipation devices.
Influence of Dzyaloshinskii–Moriya interaction on the magnetic vortex reversal in an off-centered nanocontact geometry
Authors: Li Hua-Nan , Xue Tong-Xin , Chen Lei , Sui Ying-Rui , Wei Mao-Bin
Published: January 2022

The influence of Dzyaloshinskii–Moriya interaction (DMI) on the vortex reversal driven by an out-of-plane spin-polarized current in an off-centered nanocontact structure is investigated. The simulation results show that DMI plays a vital role in vortex core reversal, including reversal current density, reversal velocity and reversal time. Under the influence of DMI, magnetic vortices still reverse polarity through the nucleation and annihilation of vortex and anti-vortex, with some peculiar characteristics. These results open up new possibilities for the application of magnetic vortex-based spin-transfer encryption nano-storage.
Wet etching and passivation of GaSb-based very long wavelength infrared detectors
Authors: Xu Xue-Yue , Jiang Jun-Kai , Chen Wei-Qiang , Cui Su-Ning , Zhou Wen-Guang , Li Nong , Chang Fa-Ran , Wang Guo-Wei , Xu Ying-Qiang , Jiang Dong-Wei , Wu Dong-Hai , Hao Hong-Yue , Niu Zhi-Chuan
Published: January 2022

The etching and passivation processes of very long wavelength infrared (VLWIR) detector based on the InAs/GaSb/AlSb type-II superlattice have been studied. By studying the effect of each component in the citric acid solution (citric acid, phosphoric acid, hydrogen peroxide, deionized water), the best solution ratio is obtained. After comparing different passivation materials such as sulfide + SiO2, Al2O3, Si3N4 and SU8, it is found that SU8 passivation can reduce the dark current of the device to a greater degree. Combining this wet etching and SU8 passivation, the R
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A of VLWIR detector with a mesa diameter of 500 μm is about 3.6 Ω⋅cm2 at 77 K.
High-quality CdS quantum dots sensitized ZnO nanotube array films for superior photoelectrochemical performance
Authors: Gong Qian-Qian , Zhao Yun-Long , Zhang Qi , Hu Chun-Yong , Liu Teng-Fei , Zhang Hai-Feng , Yin Guang-Chao , Sun Mei-Ling
Published: January 2022

The surface characteristics of ZnO were synthetically optimized by a self-designed simultaneous etching and W-doping hydrothermal method utilizing as-prepared ZnO nanorod (NR) array films as the template. Benefiting from the etching and regrowth process and the different structural stabilities of the various faces of ZnO NRs, the uniquely etched and W-doped ZnO (EWZ) nanotube (NT) array films with larger surface area, more active sites and better energy band structure were used to improve the photoelectrochemical (PEC) performance and the loading quality of CdS quantum dots (QDs). On the basis of their better surface characteristics, the CdS QDs were uniformly loaded on EWZ NT array film with a good coverage ratio and interface connection; this effectively improved the light-harvesting ability, charge transportation and separation as well as charge injection efficiency during the PEC reaction. Therefore, all the CdS QD-sensitized EWZ NT array films exhibited significantly enhanced PEC performance. The CdS/EWZ-7 composite films exhibited the optimal photocurrent density with a value of 12 mA⋅cm−2, 2.5 times higher than that of conventional CdS/ZnO-7 composite films under the same sensitization times with CdS QDs. The corresponding etching and optimizing mechanisms were also discussed.
The 50 nm-thick yttrium iron garnet films with perpendicular magnetic anisotropy
Authors: Chen Shuyao , Xie Yunfei , Yang Yucong , Gao Dong , Liu Donghua , Qin Lin , Yan Wei , Tan Bi , Chen Qiuli , Gong Tao , Li En , Bi Lei , Liu Tao , Deng Longjiang
Published: January 2022

Yttrium iron garnet (YIG) films possessing both perpendicular magnetic anisotropy (PMA) and low damping would serve as ideal candidates for high-speed energy-efficient spintronic and magnonic devices. However, it is still challenging to achieve PMA in YIG films thicker than 20 nm, which is a major bottleneck for their development. In this work, we demonstrate that this problem can be solved by using substrates with moderate lattice mismatch with YIG so as to suppress the excessive strain-induced stress release as increasing the YIG thickness. After carefully optimizing the growth and annealing conditions, we have achieved out-of-plane spontaneous magnetization in YIG films grown on sGGG substrates, even when they are as thick as 50 nm. Furthermore, ferromagnetic resonance and spin pumping induced inverse spin Hall effect measurements further verify the good spin transparency at the surface of our YIG films.
Strengthening and softening in gradient nanotwinned FCC metallic multilayers
Authors: Tian Yuanyuan , Luo Gangjie , Fang Qihong , Li Jia , Peng Jing
Published: January 2022

Plastic-deformation behaviors of gradient nanotwinned (GNT) metallic multilayers are investigated in nanoscale via molecular dynamics simulation. The evolution law of deformation behaviors of GNT metallic multilayers with different stacking fault energies (SFEs) during nanoindentation is revealed. The deformation behavior transforms from the dislocation dynamics to the twinning/detwinning in the GNT Ag, Cu, to Al with SFE increasing. In addition, it is found that the GNT Ag and GNT Cu strengthen in the case of a larger twin gradient based on more significant twin boundary (TB) strengthening and dislocation strengthening, while the GNT Al softens due to more TB migration and dislocation nucleation from TB at a larger twin gradient. The softening mechanism is further analyzed theoretically. These results not only provide an atomic insight into the plastic-deformation behaviors of certain GNT metallic multilayers with different SFEs, but also give a guideline to design the GNT metallic multilayers with required mechanical properties.
Estimation of H ii Bubble Size Distribution from 21 cm Power Spectrum with Artificial Neural Networks
Authors: Shimabukuro Hayato , Mao Yi , Tan Jianrong
Published: January 2022

The bubble size distribution of ionized hydrogen regions probes information about the morphology of H II bubbles during reionization. Conventionally, the H II bubble size distribution can be derived from the tomographic imaging data of the redshifted 21 cm signal from the epoch of reionization, which, however, is observationally challenging even for upcoming large radio interferometer arrays. Given that these interferometers promise to measure the 21 cm power spectrum accurately, we propose a new method, which is based on artificial neural networks, to reconstruct the H II bubble size distribution from the 21 cm power spectrum. We demonstrate that reconstruction from the 21 cm power spectrum can be almost as accurate as being directly measured from the imaging data with fractional error ≲10%, even with thermal noise at the sensitivity level of the Square Kilometre Array. Nevertheless, the reconstruction implicitly exploits the modeling in reionization simulations, and hence the recovered H II bubble size distribution is not an independent summary statistic from the power spectrum, and should be used only as an indicator for understanding H II bubble morphology and its evolution.
Validation of edge turbulence codes against the TCV-X21 diverted L-mode reference case
Authors: Oliveira D.S. , Body T. , Galassi D. , Theiler C. , Laribi E. , Tamain P. , Stegmeir A. , Giacomin M. , Zholobenko W. , Ricci P. , Bufferand H. , Boedo J.A. , Ciraolo G. , Colandrea C. , Coster D. , de Oliveira H. , Fourestey G. , Gorno S. , Imbeaux F. , Jenko F. , Naulin V. , Offeddu N. , Reimerdes H. , Serre E. , Tsui C.K. , Varini N. , Vianello N. , Wiesenberger M. , Wüthrich C. , the TCV Team
Published: January 2022

Self-consistent full-size turbulent-transport simulations of the divertor and scrape-off-layer (SOL) of existing tokamaks have recently become feasible. This enables the direct comparison of turbulence simulations against experimental measurements. In this work, we perform a series of diverted ohmic L-mode discharges on the tokamak à configuration variable (TCV) tokamak, building a first-of-a-kind dataset for the validation of edge turbulence models. This dataset, referred to as TCV-X21, contains measurements from five diagnostic systems from the outboard midplane (OMP) to the divertor targets—giving a total of 45 one- and two-dimensional comparison observables in two toroidal magnetic field directions. The experimental dataset is used to validate three flux-driven 3D fluid-turbulence models—GBS, GRILLIX and TOKAM3X. With each model, we perform simulations of the TCV-X21 scenario, individually tuning the particle and power source rates to achieve a reasonable match of the upstream separatrix value of density and electron temperature. We find that the simulations match the experimental profiles for most observables at the OMP—both in terms of profile shape and absolute magnitude—while a comparatively poorer agreement is found towards the divertor targets. The match between simulation and experiment is seen to be sensitive to the value of the resistivity, the heat conductivities, the power injection rate and the choice of sheath boundary conditions. Additionally, despite targeting a sheath-limited regime, the discrepancy between simulations and experiment also suggests that the neutral dynamics should be included. The results of this validation show that turbulence models are able to perform simulations of existing devices and achieve reasonable agreement with experimental measurements. Where disagreement is found, the validation helps to identify how the models can be improved. By publicly releasing the experimental dataset and validation analysis, this work should help to guide and accelerate the development of predictive turbulence simulations of the edge and SOL.
Induced stalled flow due to roughness sensitivity for thick airfoils in modern wind turbines
Authors: Gutiérrez R , Llorente E , Ragni D
Published: January 2022

The mid-span region of wind turbine blades can be thickened to fulfil the structural requirements of the blade. Hence, thick airfoils, that were designed to operate at the root region of the blade, are moved to the mid-span region. This could not imply remarkable variations of the blade performance once its surface is smooth. However, the sensitivity of thick airfoils to roughness could cause significant aerodynamic impacts such as flow separation. This research aims to quantify the impact of the blade thickness, under smooth and rough conditions, in the annual energy production and the fatigue loads of the blade. Ten blade designs, linearly interpolated in thickness, are studied employing aero-elastic computations. The results reveal that the thickest blade increases the annual energy production by 5% with respect to the thinnest blade under rough conditions. Whereas this increase is less than 1% under smooth conditions. The loss of annual energy production varies with the blade thickness linearly for thin blades while it varies exponentially for thick blades up to 22%. Fatigue loads assessment confirmed a reduction of the damage equivalent load under smooth conditions, whereas the thickest blade increased it 28% under rough conditions.