bluuebunny/crossref_metadata_2025 huggingface dataset:
Managed pathways for CO2 mineralisation: analogy with nature and potential contribution to CCUS-led reduction targets
Authors: Hills Colin D. , Tripathi Nimisha , Carey Paula J.
Published: February 2021

We examine natural and managed pathways for CO2 mineralisation. Our study indicates that managed pathways have potential to meet 60% of the UK’s CCUS-led emission reductions by mineralising 24 Mt CO2 in selected industrial wastes by 2030.
Activation of hydrogen peroxide by the nitrate anion in micellar media
Authors: Schmidt Fabian , Zehner Bastian , Kaposi Marlene , Drees Markus , Mink János , Korth Wolfgang , Jess Andreas , Cokoja Mirza
Published: February 2021

Surface-active imidazolium nitrates activate hydrogen peroxide, which enables the epoxidation of olefins. The micelles solubilise the substrate in the aqueous oxidant phase and allow for simple product separation and catalyst recycling.
Rapid and precise tumor cell separation using the combination of size-dependent inertial and size-independent magnetic methods
Authors: Huang Di , Xiang Nan
Published: February 2021

A three-stage i-Mag device combines the passive inertial microfluidics and the active magnetophoresis method for rapid, precise, and tumor antigen-independent separation of rare tumor cells from blood.
A new strategy for the adsorption and removal of fenitrothion from real samples by active-extruded MOF (AE-MOF UiO-66) as an adsorbent
Authors: Ashouri Vahid , Adib Kourosh , Rahimi Nasrabadi Mehdi
Published: February 2021

The adsorption and removal of hazardous materials such as fenitrothion by adsorbents with high adsorption capacities and easy separation from sample solutions are highly desirable.
Molecular diversity of TEMPO-mediated cycloaddition of ketohydrazones and 3-phenacylideneoxindoles
Authors: Ye Rong , Sun Jing , Han Ying , Yan Chao-Guo
Published: February 2021

This reaction selectively proceeded via aza-Diels–Alder reaction, [3+2] cycloaddition and ring-opening of oxindole to give diverse spirooxindoles and polysubstituted pyrazoles.
Ru-tweaking of non-precious materials: the tale of a strategy that ensures both cost and energy efficiency in electrocatalytic water splitting
Authors: Anantharaj S.
Published: February 2021

This review brings out the recent developments of how the cost-wise unaffordable Ru can be used to tweak the abundant electrocatalysts of water electrosplitting to ensure both cost and energy-efficiency in the H2 generation.
A magnetic surface-enhanced Raman scattering platform for performing successive breast cancer exosome isolation and analysis
Authors: Li Guohao , Zhu Nanhang , Zhou Juan , Kang Ke , Zhou Xiaoxi , Ying Binwu , Yi Qiangying , Wu Yao
Published: February 2021

Exosome isolation and SERS are integrated into one system to realize the diagnosis of breast cancer.
Electrochemical sensor for rutin detection based on N-doped mesoporous carbon nanospheres and graphene
Authors: Zhen Qingfang , Ma Huiyuan , Jin Zhongxin , Zhu Di , Liu Xiao , Sun Yu , Zhang Chunjing , Pang Haijun
Published: February 2021

A new electrochemical sensor shows great sensing performance to rutin and high selectivity towards even 13 interfering species and realizes detection of rutin in real samples such as human serum.
Polyoxometalate driven dendrite-free zinc electrodes with synergistic effects of cation and anion cluster regulation
Authors: Wu Hai-Yang , Gu Xingxing , Huang Peng , Sun Chuang , Hu Hai , Zhong Yuan , Lai Chao
Published: February 2021

Dendrite-free Zn anodes are achieved by using the highly efficient electrolyte additives based on polyoxometalate. Both of the anions and cations of polyoxometalate play important roles in inhibiting the growth Zn dendrites.
Tracking Advanced Planetary Systems (TAPAS) with HARPS-N
Authors: Niedzielski A. , Villaver E. , Adamów M. , Kowalik K. , Wolszczan A. , Maciejewski G.
Published: February 2021

Context. We present the current status of and new results from our search for exoplanets in a sample of solar-mass evolved stars observed with the HARPS-N and the 3.6 m Telescopio Nazionale Galileo (TNG), and the High-Resolution Spectrograph (HRS) and the 9.2 m Hobby-Eberly Telescope (HET).

Aims. The aim of this project is to detect and characterize planetary-mass companions to solar-mass stars in a sample of 122 targets at various stages of evolution from the main sequence to the red giant branch, mostly subgiants and giants, selected from the Pennsylvania-Toruń Planet Search sample, and to use this sample to study relations between stellar properties, such as metallicity, luminosity, and the planet occurrence rate.

Methods. This work is based on precise radial velocity (RV) measurements. We have observed the program stars for up to 14 yr with the HET/HRS and the TNG/HARPS-N.

Results. We present the analysis of RV measurements with the HET/HRS and the TNG/HARPS-N of four solar-mass stars, HD 4760, HD 96992, BD+02 3313, and TYC 0434-04538-1. We found that HD 4760 hosts a companion with a minimum mass of 13.9 MJ (a = 1.14 au, e = 0.23); HD 96992 is a host to a m sin i = 1.14 MJ companion on an a = 1.24 au and e = 0.41 orbit, and TYC 0434-04538-1 hosts an m sin i = 6.1 MJ companion on an a = 0.66 au and e = 0.08 orbit. In the case of BD+02 3313 we found a correlation between the measured RVs and one of the stellar activity indicators, suggesting that the observed RV variations may either originate in stellar activity or be caused by the presence of an unresolved companion. We also discuss the current status of the project and a statistical analysis of the RV variations in our sample of target stars.

Conclusions. In our sample of 122 solar-mass stars, 49 ± 5% of them appear to be single and 16 ± 3% spectroscopic binaries. The three giants hosting low-mass companions presented in this paper join the six previously identified giants in the sample.
A search for a fifth planet around HR 8799 using the star-hopping RDI technique at VLT/SPHERE
Authors: Wahhaj Z. , Milli J. , Romero C. , Cieza L. , Zurlo A. , Vigan A. , Peña E. , Valdes G. , Cantalloube F. , Girard J. , Pantoja B.
Published: February 2021

Context.Direct imaging of extrasolar giant planets demands the highest possible contrasts (ΔH ≳ 10 mag) at the smallest angular separations (∼0.1″) from the star. We present an adaptive optics observing method, called star-hopping, recently offered as standard queue observing (service mode) for the SPHERE instrument at the VLT. The method uses reference difference imaging (RDI) but, unlike earlier RDI applications, images of a reference star for PSF subtraction are obtained within minutes of observing the target star.

Aims.We aim to significantly gain in contrast beyond the conventional angular differencing imaging (ADI) method to search for a fifth planet at separations less than 10 au, interior to the four giant planets of the HR 8799 system. The most likely semimajor axes allowed for this hypothetical planet, which were estimated via dynamical simulations in earlier works, were 7.5 au and 9.7 au within a mass range of 1–8MJup.

Methods.We obtained 4.5 h of simultaneous low-resolution integral field spectroscopy (R ∼ 30,Y − Hband with IFS) and dual-band imaging (K1 andK2 bands with IRDIS) of the HR 8799 system, interspersed with observations of a reference star. The reference star was observed for about one-third of the total time and generally needs to be of similar brightness (ΔR ≲ 1 mag) and separated on sky by ≲1–2°. The hops between stars were made every 6–10 min, with only 1 min gaps in on-sky integration per hop.

Results.We did not detect the hypothetical fifth planet at the most plausible separations, 7.5 and 9.7 au, down to mass limits of 3.6MJupand 2.8MJup, respectively, but attained an unprecedented contrast limit of 11.2 magnitudes at 0.1″. We detected all four planets with high signal-to-noise ratios. TheYJHspectra for planetsc,dwere detected with redderH-band spectral slopes than found in earlier studies. As noted in previous works, the planet spectra are matched very closely by some red field dwarfs. Finally, comparing the current locations of the planets to orbital solutions, we found that planetseandcare most consistent with coplanar and resonant orbits. We also demonstrated that with star-hopping RDI, the contrast improvement at 0.1″ separation can be up to 2 mag.

Conclusions.Since ADI, meridian transit and the concomitant sky rotation are not needed, the time of observation can be chosen from within a window that is two to three times larger. In general, star-hopping can be used for stars fainter thanR = 4 magnitudes, since for these a reference star of suitable brightness and separation is usually available.
Infrared photometry and CaT spectroscopy of globular cluster M 28 (NGC 6626)
Authors: Moni Bidin C. , Mauro F. , Contreras Ramos R. , Zoccali M. , Reinarz Y. , Moyano M. , González-Díaz D. , Villanova S. , Carraro G. , Borissova J. , Chené A.-N. , Cohen R. E. , Geisler D. , Kurtev R. , Minniti D.
Published: February 2021

Context. Recent studies show that the inner Galactic regions host genuine bulge globular clusters, but also halo intruders, complex remnants of primordial building blocks, and objects likely accreted during major merging events.

Aims. In this study we focus on the properties of M 28, a very old and massive cluster currently located in the Galactic bulge.

Methods. We analysed wide-field infrared photometry collected by the VVV survey, VVV proper motions, and intermediate-resolution spectra in the calcium triplet range for 113 targets in the cluster area.

Results. Our results in general confirm previous estimates of the cluster properties available in the literature. We find no evidence of differences in metallicity between cluster stars, setting an upper limit of Δ[Fe/H] < 0.08 dex to any internal inhomogeneity. We confirm that M 28 is one of the oldest objects in the Galactic bulge (13–14 Gyr). From this result and the literature data, we find evidence of a weak age–metallicity relation among bulge globular clusters that suggests formation and chemical enrichment. In addition, wide-field density maps show that M 28 is tidally stressed and that it is losing mass into the general bulge field.

Conclusions. Our study indicates that M 28 is a genuine bulge globular cluster, but its very old age and its mass loss suggest that this cluster could be the remnant of a larger structure, possibly a primeval bulge building block.
Transition to turbulence in nonuniform coronal loops driven by torsional Alfvén waves
Authors: Díaz-Suárez Sergio , Soler Roberto
Published: February 2021

Both observations and numerical simulations suggest that Alfvénic waves may carry sufficient energy to sustain the hot temperatures of the solar atmospheric plasma. However, the thermalization of wave energy is inefficient unless very short spatial scales are considered. Phase mixing is a mechanism that can take energy down to dissipation lengths, but it operates over too long a timescale. Here, we study how turbulence, driven by the nonlinear evolution of phase-mixed torsional Alfvén waves in coronal loops, is able to take wave energy down to the dissipative scales much faster than the theory of linear phase mixing predicts. We consider a simple model of a transversely nonuniform cylindrical flux tube with a constant axial magnetic field. The flux tube is perturbed by the fundamental mode of standing torsional Alfvén waves. We solved the three-dimensional ideal magnetohydrodynamics equations numerically to study the temporal evolution. Initially, torsional Alfvén waves undergo the process of phase mixing because of the transverse variation of density. After only few periods of torsional waves, azimuthal shear flows generated by phase mixing eventually trigger the Kelvin-Helmholtz instability (KHi), and the flux tube is subsequently driven to a turbulent state. Turbulence is very anisotropic and develops transversely only to the background magnetic field. After the onset of turbulence, the effective Reynolds number decreases in the flux tube much faster than in the initial linear stage governed by phase mixing alone. We conclude that the nonlinear evolution of torsional Alfvén waves, and the associated KHi, is a viable mechanism for the onset of turbulence in coronal loops. Turbulence can significantly speed up the generation of small scales. Enhanced deposition rates of wave energy into the coronal plasma are therefore expected.
New horizons in black hole astrophysics
Authors: Blandford Roger
Published: February 2021

Black holes, a seemingly inevitable consequence of Einstein’s general theory of relativity and stellar and galactic evolution are being observed in many new ways with masses ranging from roughly three to ten billion solar masses. Their masses and spins determine how they power the most luminous objects in the universe and impact their environments.
Exogenous nitric oxide stimulates early egress of Eimeria tenella sporozoites from primary chicken kidney cells in vitro
Authors: Yan Xinlei , Han Wenying , Liu Xianyong , Suo Xun
Published: February 2021

Egress plays a vital role in the life cycle of apicomplexan parasites including Eimeria tenella, which has been attracting attention from various research groups. Many recent studies have focused on early egress induced by immune molecules to develop a new method of apicomplexan parasite elimination. In this study, we investigated whether nitric oxide (NO), an immune molecule produced by different types of cells in response to cytokine stimulation, could induce early egress of eimerian sporozoites in vitro. Eimeria tenella sporozoites were extracted and cultured in primary chicken kidney cells. The number of sporozoites egressed from infected cells was analyzed by flow cytometry after treatment with NO released by sodium nitroferricyanide (II) dihydrate. The results showed that exogenous NO stimulated the rapid egress of E. tenella sporozoites from primary chicken kidney cells before replication of the parasite. We also found that egress was dependent on intra-parasitic calcium ion (Ca2+) levels and no damage occurred to host cells after egress. The virulence of egressed sporozoites was significantly lower than that of fresh sporozoites. The results of this study contribute to a novel field examining the interactions between apicomplexan parasites and their host cells, as well as that of the clearance of intracellular pathogens by the host immune system.
A diffuse interface approach for disperse two-phase flows involving dual-scale kinematics of droplet deformation based on geometrical variables
Authors: Cordesse Pierre , Di Battista Ruben , Chevalier Quentin , Matuszewski Lionel , Ménard Thibaut , Kokh Samuel , Massot Marc
Published: February 2021

The purpose of this contribution is to derive a reduced-order two-phase flow model in- cluding interface subscale modeling through geometrical variables based on Stationary Action Principle (SAP) and Second Principle of Thermodynamics in the spirit of [6, 14]. The derivation is conducted in the disperse phase regime for the sake of clarity but the resulting paradigm can be used in a more general framework. One key issue is the definition of the proper potential and kinetic energies in the Lagrangian of the system based on geometrical variables (Interface area density, mean and Gauss curvatures...), which will drive the subscale kinematics and dissipation, and their coupling with large scales of the flow. While [14] relied on bubble pulsation, that is normal deformation of the interface with shape preservation related to pressure changes, we aim here at tackling inclusion deformation at constant volume, thus describing self-sustained oscillations. In order to identify the proper energies, we use Direct Numerical Simulations (DNS) of oscillating droplets using ARCHER code and recently devel- oped library, Mercur(v)e, for mean geometrical variable evaluation and analysis preserving topological invariants. This study is combined with historical analytical studies conducted in the small perturba- tion regime and shows that the proper potential energy is related to the surface difference compared to the spherical minimal surface. A geometrical quasi-invariant is also identified and a natural definition of subscale momentum is proposed. The set of Partial Differential Equations (PDEs) including the conservation equations as well as dissipation source terms are eventually derived leading to an original two-scale diffuse interface model involving geometrical variables.
Some mathematical properties of a barotropic multiphase flow model
Authors: Saleh Khaled , Seguin Nicolas
Published: February 2021

We study a model for compressible multiphase flows involving N non miscible barotopic phases where N is arbitrary. This model boils down to the barotropic Baer-Nunziato model when N = 2. We prove the weak hyperbolicity property, the non-strict convexity of the natural mathematical entropy, and the existence of a symmetric form.
A conservative saint-venant type model to describe the dynamics of thin partially wetting films with regularized forces at the contact line
Authors: Trontin Pierre , Lallement Julien , Villedieu Philippe
Published: February 2021

This paper deals with the numerical simulation of thin liquid films flowing on partially wetting solid substrates. A 2D Saint-Venant like model is proposed. Its originality lies in the conservative formulation of the capillary forces and in the model used for the disjoining pressure that accounts for the contact line capillary forces. A finite volume scheme is proposed for the resolution of the system and various numerical examples are presented and discussed. In particular, when the mesh resolution is fine enough, the model is proved to be able to predict correctly the spreading of a film with the exact contact angle in the vicinity of the contact line. When the mesh size is larger than the film thickness (which could be the case for many industrial applications), it is of course no longer possible to recover the contact angle. However, the model is proved to correctly predict the spreading of the film. This important feature is related to the thermodynamic consistency of the model in the sense that the latter ensures by construction the decrease of the film total free energy in the absence of external driving forces.
Improving sample preheating capabilities for dynamic loading on high-pulsed power drivers
Authors: Vich J. , Barbarin Y. , Le Blanc G. , Chauvin C. , Ribière M. , Maisonny R. , Duvaut T. , d’Almeida T.
Published: February 2021

The CEA operates several High-Pulsed Power (HPP) drivers for dynamic loading experiments. The aim of these experiments is to provide quantitative information about the response of various materials of interest, mainly under quasi-isentropic compression. In order to improve our ability to explore these materials’ behavior over a wide range of thermodynamic paths and starting from various non-ambient conditions, we developed a device capable of pre-heating both metallic and nonmetallic samples up to several hundred degrees prior to loading. This device is based on conductive heating and on a configuration that allows homogeneous heating with unprecedented temperature stability on our HPP platforms. Moreover, it is designed to allow efficient sample heating, within extremely severe electromagnetic environments associated with such platforms. The main features of this preheating device, whose design was guided by extensive thermal simulations, are presented, along with various technical solutions that enabled its insertion in a reliable experimental configuration on our HPP drivers. The results obtained from preliminary experiments on a composite material (carbon fibers embedded in epoxy resin) and on a high purity copper sample preheated to 323 K and 573 K, respectively, are presented. The performance and robustness of this heating device are potentially valuable for extending the range of studies in dynamic loading experiments for various materials under ramp compression using HPP drivers.
NaCl aggregation in water at elevated temperatures and pressures: Comparison of classical force fields
Authors: Patel Lara A. , Yoon Tae Jun , Currier Robert P. , Maerzke Katie A.
Published: February 2021

The properties of water vary dramatically with temperature and density. This can be exploited to control its effectiveness as a solvent. Thus, supercritical water is of keen interest as solvent in many extraction processes. The low solubility of salts in lower density supercritical water has even been suggested as a means of desalination. The high temperatures and pressures required to reach supercritical conditions can present experimental challenges during collection of required physical property and phase equilibria data, especially in salt-containing systems. Molecular simulations have the potential to be a valuable tool for examining the behavior of solvated ions at these high temperatures and pressures. However, the accuracy of classical force fields under these conditions is unclear. We have, therefore, undertaken a parametric study of NaCl in water, comparing several salt and water models at 200 bar–600 bar and 450 K–750 K for a range of salt concentrations. We report a comparison of structural properties including ion aggregation, hydrogen bonding, density, and static dielectric constants. All of the force fields qualitatively reproduce the trends in the liquid phase density. An increase in ion aggregation with decreasing density holds true for all of the force fields. The propensity to aggregate is primarily determined by the salt force field rather than the water force field. This coincides with a decrease in the water static dielectric constant and reduced charge screening. While a decrease in the static dielectric constant with increasing NaCl concentration is consistent across all model combinations, the salt force fields that exhibit more ionic aggregation yield a slightly smaller dielectric decrement.
Improved accuracy and transferability of molecular-orbital-based machine learning: Organics, transition-metal complexes, non-covalent interactions, and transition states
Authors: Husch Tamara , Sun Jiace , Cheng Lixue , Lee Sebastian J. R. , Miller Thomas F.
Published: February 2021

Molecular-orbital-based machine learning (MOB-ML) provides a general framework for the prediction of accurate correlation energies at the cost of obtaining molecular orbitals. The application of Nesbet’s theorem makes it possible to recast a typical extrapolation task, training on correlation energies for small molecules and predicting correlation energies for large molecules, into an interpolation task based on the properties of orbital pairs. We demonstrate the importance of preserving physical constraints, including invariance conditions and size consistency, when generating the input for the machine learning model. Numerical improvements are demonstrated for different datasets covering total and relative energies for thermally accessible organic and transition-metal containing molecules, non-covalent interactions, and transition-state energies. MOB-ML requires training data from only 1% of the QM7b-T dataset (i.e., only 70 organic molecules with seven and fewer heavy atoms) to predict the total energy of the remaining 99% of this dataset with sub-kcal/mol accuracy. This MOB-ML model is significantly more accurate than other methods when transferred to a dataset comprising of 13 heavy atom molecules, exhibiting no loss of accuracy on a size intensive (i.e., per-electron) basis. It is shown that MOB-ML also works well for extrapolating to transition-state structures, predicting the barrier region for malonaldehyde intramolecular proton-transfer to within 0.35 kcal/mol when only trained on reactant/product-like structures. Finally, the use of the Gaussian process variance enables an active learning strategy for extending the MOB-ML model to new regions of chemical space with minimal effort. We demonstrate this active learning strategy by extending a QM7b-T model to describe non-covalent interactions in the protein backbone–backbone interaction dataset to an accuracy of 0.28 kcal/mol.
Optical and physical properties of hydrocarbons with metal impurities in the warm dense matter regime
Authors: Cao Yu , Chu Yanyun , Wang Zhen , Qi Jianmin , Zhou Lin , Li Zhenghong
Published: February 2021

The hydrocarbon (CH) polymer is often chosen as the converter material with potential applications to Z-pinch driven dynamic hohlraum implosion experiments. Its physical and optical properties in the warm dense matter regime are important for dynamic hohlraum platform designs. Using the quantum molecular dynamics (QMD) method, we have obtained the equation of state, absorption coefficient, and reflectivity of hydrocarbon and Al–CH mixtures with the temperature and density ranging from 104–106 K and 0.1–0.9 g/cm3, respectively. The QMD-predicted principal Hugoniot data are compared with experiments as well as the theoretical calculations, and both show good agreement. The optical reflectivity from the corresponding dielectric functions is calculated using the corrected refraction index of the ambient (n0 = 1.59). Besides, we have further analyzed the atomic structure and bond dissociation process of polystyrene and Al–CH mixture systems using a bond tracking method with the temperature ranging from 1000 K to 10 000 K. The Al impurities have a slightly promoting effect on the initial stage of polystyrene pyrolysis. The calculation results can be helpful for future theoretical and experimental studies in high energy density physics research.
Non-linear ultrasonic and viscoelastic properties of gelatine investigated in the temperature range of 30 °C–60 °C
Authors: Heyns Jan Dirk , Ahmed Mohamed Esam T. , Declercq Nico F.
Published: February 2021

Analysis based on the determination of the multifactorial non-linearity parameter (β) is a promising non-destructive investigation and testing technique. The contribution of temperature variations on the non-linear coefficient is known to be lower than that of hydrostatic pressure changes. We investigated the effect of temperature on the non-linearity parameter in the range 30 °C–60 °C for a viscous, gelatinous compound, resulting from controlled hydrolysis of the collagen protein. Considerable thermal effects are realized and are related to changes in viscous and elastic properties. Remarkable changes in the non-linearity coefficient at temperatures corresponding to the transition temperature of gelatine of 60 °C indicate a signature while no outspoken hysteresis effects were realized with cyclic temperature sweeps. Despite the non-Newtonian nature of the gel, our experiments show comparability to water within the examined range of temperature, which corresponds to a wavelength shift of about 40 μm.
Impact of area scaling on the ferroelectric properties of back-end of line compatible Hf0.5Zr0.5O2 and Si:HfO2-based MFM capacitors
Authors: Francois T. , Grenouillet L. , Coignus J. , Vaxelaire N. , Carabasse C. , Aussenac F. , Chevalliez S. , Slesazeck S. , Richter C. , Chiquet P. , Bocquet M. , Schroeder U. , Mikolajick T. , Gaillard F. , Nowak E.
Published: February 2021

Scaling of planar HfO2-based ferroelectric capacitors is investigated experimentally by varying the capacitor area within five orders of magnitude, under the scope of a limited thermal budget for crystallization. Both Hf0.5Zr0.5O2 (HZO) and Si-doped HfO2 (HSO)-based metal/ferroelectric/metal capacitors with a 10 nm dielectric film thickness and TiN electrodes are demonstrated to be ferroelectric when integrated in a back-end of line (BEOL) of 130 nm CMOS technology, with a maximum thermal budget below 500 °C. When the area of the ferroelectric capacitors is scaled down from 7850 μm2 to 0.28 μm2, no degradation of the remanent polarization (2·PR > 10 μC/cm2 for HSO, > 30 μC/cm2 for HZO) or of the switching kinetics (down to 100 ns at 3 V) is observed. Significant improvement of the field cycling endurance is demonstrated upon area scaling, consistent with the reduction of the total number of defects when devices are shrunk. The results pave the way for future BEOL demonstrations in 130 nm and more advanced nodes with record endurance similar to perovskite ferroelectrics.
Theoretical investigation of a novel xylene-based light-driven unidirectional molecular motor
Authors: Romeo-Gella F. , Corral I. , Faraji S.
Published: February 2021

In this study, the working mechanism of the first light-driven rotary molecular motors used to control an eight-base-pair DNA hairpin has been investigated. In particular, this linker was reported to have promising photophysical properties under physiological conditions, which motivated our work at the quantum mechanical level. Cis–trans isomerization is triggered by photon absorption at wavelengths ranging 300 nm–400 nm, promoting the rotor to the first excited state, and it is mediated by an energy-accessible conical intersection from which the ground state is reached back. The interconversion between the resulting unstable isomer and its stable form occurs at physiological conditions in the ground state and is thermally activated. Here, we compare three theoretical frameworks, generally used in the quantum description of medium-size chemical systems: Linear-Response Time-Dependent Density Functional Theory (LR-TDDFT), Spin-Flip TDDFT (SF-TDDFT), and multistate complete active space second-order perturbation theory on state-averaged complete active space self consistent field wavefunctions (MS-CASPT2//SA-CASSCF). In particular, we show the importance of resorting to a multireference approach to study the rotational cycle of light-driven molecular motors due to the occurrence of geometries described by several configurations. We also assess the accuracy and computational cost of the SF-TDDFT method when compared to MS-CASPT2 and LR-TDDFT.
Sub-10 nm spatial resolution for electrical properties measurements using bimodal excitation in electric force microscopy
Authors: Kaja Khaled , Mariolle Denis , Chevalier Nicolas , Naja Adnan , Jouiad Mustapha
Published: February 2021

We demonstrate that under ambient and humidity-controlled conditions, operation of bimodal excitation single-scan electric force microscopy with no electrical feedback loop increases the spatial resolution of surface electrical property measurements down to the 5 nm limit. This technical improvement is featured on epitaxial graphene layers on SiC, which is used as a model sample. The experimental conditions developed to achieve such resolution are discussed and linked to the stable imaging achieved using the proposed method. The application of the herein reported method is achieved without the need to apply DC bias voltages, which benefits specimens that are highly sensitive to polarization. Besides, it allows the simultaneous parallel acquisition of surface electrical properties (such as contact potential difference) at the same scanning rate as in amplitude modulation atomic force microscopy (AFM) topography measurements. This makes it attractive for applications in high scanning speed AFM experiments in various fields for material screening and metrology of semiconductor systems.
The continuous eddy simulation capability of velocity and scalar probability density function equations for turbulent flows
Authors: Heinz Stefan
Published: February 2021

There is a well developed spectrum of computational methods for turbulent flows: modeling methods such as Reynolds-averaged Navier–Stokes (RANS) and probability density function (PDF) methods, and resolving methods such as large eddy simulation (LES) and filtered density function (FDF) methods. However, the applicability of RANS/PDF methods is limited to flows that do not essentially require the inclusion of resolved motion, and LES/FDF methods are well applicable if resolution criteria can be satisfied [which is often infeasible for very high Reynolds number (Re) wall-bounded turbulent flows]. A highly attractive approach to overcome these problems is the design of hybrid RANS–LES methods, which can be used with varying amounts of resolved and modeled motions. However, this approach faces the problem to ensure communication and balancing of resolved and modeled motions. A well working solution to this problem was presented recently for non-homogeneous flows with respect to velocity two-equation eddy viscosity turbulence models. Exact analytical results regarding the extension of these methods to velocity and passive scalar PDF/FDF methods and their implied RANS/LES equations are presented here. The latter matters with respect to the justification of the theoretical basis of new hybrid methods (realizability) and the availability of a hierarchy of simple and advanced simulation methods (including passive scalar transport). Based on the continuous mode redistribution mechanism, the new simulation methods are capable of providing reliable predictions of very high Re turbulent flows, which cannot be accomplished by using existing techniques.
Charge–spin interconversion and its applications in magnetic sensing
Authors: Wu Yihong , Xu Yanjun , Luo Ziyan , Yang Yumeng , Xie Hang , Zhang Qi , Zhang Xinhai
Published: February 2021

Charge–spin interconversion provides an effective way to generate spin current, spin–orbit torque, and unconventional magnetoresistance that is different from the magnetoresistance originated from spin-polarized current. A widely studied system that leads to all these phenomena is the ferromagnet/heavy metal bilayer, in which spin accumulation/current is generated through either the spin Hall effect in the heavy metal layer or Rashba–Edelstein effect at the ferromagnet/heavy metal interface. The subsequent interaction of the current-induced spins with the ferromagnet generates spin–orbit torque, and the inverse conversion of the backflow spin current to charge current in the heavy metal layer leads to different types of magnetoresistances. Many proof-of-concept devices and applications have been demonstrated based on the spin–orbit torque and magnetoresistance in the bilayer system, including non-volatile memory, logic, nano-oscillator, magnetic sensor, neuromorphic and scholastic computing, etc. In addition to the bilayer systems, recently there is also a growing interest in charge–spin interconversion in single-layer ferromagnets. In this Perspective, we first introduce the charge–spin interconversion in different systems based on phenomenological models, after which we show how the spin–orbit torque and spin Hall magnetoresistance in ferromagnet/heavy metal bilayers can be exploited for magnetic sensing applications. We also discuss charge–spin interconversion in single-layer ferromagnets via the anomalous Hall effect.
A low noise cryogen-free scanning tunneling microscope–superconducting magnet system with vacuum sample transfer
Authors: Chaudhary Saurabh , Panda Janmey Jay , Mundlia Suman , Mathimalar S. , Ahmedof Aathif , Raman Karthik V.
Published: February 2021

Imaging atomically resolved surfaces and performing spectroscopy of exotic surfaces at cryogenic temperature in the presence of the magnetic field is an engineering challenge. Additionally, performing these measurements in an all-cryogen-free environment compounds the above complexity due to the associated vibration and acoustic noise generated by the running of cryogenic cold heads. We here report successful integration of a cryogen-free scanning tunneling microscope (STM) with a cryogen-free superconducting vector-magnet, connected to an ultra-high vacuum cluster assembly for in situ sample transfer. We present details of the integration involving vibration and electrical noise isolation procedures allowing for operation of the STM at extremely low noise levels below 30 fA/Hz during normal operations of the complete vacuum-line assembly with multiple turbomolecular pumps. We demonstrate the above STM capability at cryogenic temperature and in the presence of the magnetic field through atomic resolution imaging of graphite and thin films of gold on the mica substrate transferred in situ to the STM chamber. We also demonstrate spectroscopy signatures of the superconducting gap in MgB2 thin films. The design of our in-house customized cluster-vacuum-line assembly provides unsought opportunities in continuous uninterrupted imaging of ultra-clean in-vacuum grown surfaces without the need for cryogenic refills in either the STM or the magnet.
Guiding light with singular beams in nanoplasmonic colloids
Authors: Balbuena Ortega A. , Torres-González F. E. , López Gayou V. , Delgado Macuil R. , Cardoso Sakamoto J. E. H. , Arzola A. V. , Assanto G. , Volke-Sepulveda K.
Published: February 2021

We investigate the nonlinear propagation of light beams with complex phase and intensity structures, including a Gaussian-embedded vortex, a Bessel vortex, and a Bessel-cosine necklace. We employ a colloidal suspension of bio-synthesized plasmonic gold nanoparticles, where a self-defocusing response is mediated by absorption at the laser wavelength (532 nm). We show that, by means of nonlocal nonlinearity, these structured two-dimensional beams with on-axis singularity can counteract the diffraction of the dark core and guide therein a coaxial Gaussian probe of different wavelengths (633 nm) and lower intensities. Angular steering of the confined probe is also demonstrated by tilting the propagation direction of the pump.
A phaseless auxiliary-field quantum Monte Carlo perspective on the uniform electron gas at finite temperatures: Issues, observations, and benchmark study
Authors: Lee Joonho , Morales Miguel A. , Malone Fionn D.
Published: February 2021

We investigate the viability of the phaseless finite-temperature auxiliary-field quantum Monte Carlo (ph-FT-AFQMC) method for ab initio systems using the uniform electron gas as a model. Through comparisons with exact results and FT coupled cluster theory, we find that ph-FT-AFQMC is sufficiently accurate at high to intermediate electronic densities. We show, both analytically and numerically, that the phaseless constraint at FT is fundamentally different from its zero-temperature counterpart (i.e., ph-ZT-AFQMC), and generally, one should not expect ph-FT-AFQMC to agree with ph-ZT-AFQMC in the low-temperature limit. With an efficient implementation, we are able to compare exchange-correlation energies to the existing results in the thermodynamic limit and find that the existing parameterizations are highly accurate. In particular, we found that ph-FT-AFQMC exchange-correlation energies are in better agreement with a known parameterization than is restricted path-integral MC in the regime of Θ ≤ 0.5 and rs ≤ 2, which highlights the strength of ph-FT-AFQMC.
A universal method of chaos cascade and its applications
Authors: Yuan Fang , Li Yuxia , Wang Guangyi
Published: February 2021

This paper proposes a universal method for a cascade chaotic system (CCS). CCSs may own better performances, including larger maximum Lyapunov exponents, extended full mapping range of chaos, and more coefficient variations. The chaos-cascade theorems had been proposed in our previous papers, which are more suitable for discrete chaotic systems with the same domain. In this paper, we further improve a universal method to normalize arbitrary discrete chaotic systems for constructing a series of CCSs. Besides, the inheritance and enhancement of robustness from the subsystem are first explored for CCSs. Finally, the designed CCS is implemented on field programmable gate array board. The generated chaotic sequences are obtained by an oscilloscope and tested by NIST software.
'I think they might just go to the doctor': qualitatively examining the (un)acceptability of newer HIV testing approaches among Vietnamese-born migrants in greater-Brisbane, Queensland, Australia
Authors: Blondell Sarah J. , Debattista Joseph , Griffin Mark P. , Durham Jo
Published: February 2021

Background
In high-income countries (HICs), migrants often have higher rates of late diagnosis of HIV than the host population. Timely HIV testing has significant implications for HIV prevention and management. Newer HIV testing approaches, namely provider-initiated testing and counselling (PITC), HIV rapid testing (HIV RT) and HIV self-testing (HIV ST), aim to reach those populations most at risk and, particularly, those who have not previously tested for HIV. Methods: This study used semi-structured interviews to examine the (un)acceptability, barriers and facilitators to newer HIV testing approaches (i.e. PITC, HIV RT and HIV ST) among Vietnamese-born migrants (n = 10) in greater-Brisbane, Queensland, Australia. Results: Vietnamese-born migrants had mixed perspectives on the (un)acceptability of newer HIV testing approaches. PITC was largely viewed by participants as a facilitator to HIV testing for Vietnamese-born migrants. Likewise, HIV RT (undertaken by a doctor in a medical setting, as opposed to a trained community member in a community setting) was generally considered to facilitate HIV testing. HIV ST was largely not considered acceptable to Vietnamese-born migrants and they would prefer to go to a doctor for HIV testing. Several factors were identified that either facilitate or act as barriers to newer HIV testing approaches, including privacy; cost of (accessing) HIV testing; comfort and convenience; healthcare provider relationship; risk perception; symptoms; and technical and emotional support. Conclusions: There is a need to understand migrants’ HIV testing preferences if poorer HIV-related outcomes are to be overcome. The findings from this study show a preference for doctor-centred HIV testing, due to enhanced privacy, accuracy and support.
Computational analyses reveal spatial relationships between nuclear pore complexes and specific lamins
Authors: Kittisopikul Mark , Shimi Takeshi , Tatli Meltem , Tran Joseph Riley , Zheng Yixian , Medalia Ohad , Jaqaman Khuloud , Adam Stephen A. , Goldman Robert D.
Published: February 2021

Nuclear lamin isoforms form fibrous meshworks associated with nuclear pore complexes (NPCs). Using datasets prepared from subpixel and segmentation analyses of 3D–structured illumination microscopy images of WT and lamin isoform knockout mouse embryo fibroblasts, we determined with high precision the spatial association of NPCs with specific lamin isoform fibers. These relationships are retained in the enlarged lamin meshworks of Lmna−/− and Lmnb1−/− fibroblast nuclei. Cryo-ET observations reveal that the lamin filaments composing the fibers contact the nucleoplasmic ring of NPCs. Knockdown of the ring-associated nucleoporin ELYS induces NPC clusters that exclude lamin A/C fibers but include LB1 and LB2 fibers. Knockdown of the nucleoporin TPR or NUP153 alters the arrangement of lamin fibers and NPCs. Evidence that the number of NPCs is regulated by specific lamin isoforms is presented. Overall the results demonstrate that lamin isoforms and nucleoporins act together to maintain the normal organization of lamin meshworks and NPCs within the nuclear envelope.
New twists in humoral immune regulation by SLAM family receptors
Authors: Qi Hai
Published: February 2021

SLAM family receptors are involved in humoral immune regulation. In this issue of JEM, Zhong et al. (2021. J. Exp. Med.https://doi.org/10.1084/jem.20200756) provide evidence that these receptors collectively suppress germinal center reaction but promote production of antigen-specific antibodies.
Not so transport incompetent after all: Revisiting a CLC-7 mutant sheds new mechanistic light on lysosomal physiology
Authors: Accardi Alessio
Published: February 2021

Accardi reviews data on the lysosomal 2 Cl−/1 H+ antiporter ClC-7.
Generation of third-order parametric down-conversion photons via weak nonlinearities
Authors: He Ying-Qiu , Ding Dong , Yan Feng-Li , Gao Ting
Published: February 2021

A higher-order parametric down-conversion (PDC) photon state is amazingly different from the states involving independent photon pairs. We focus on the third-order PDC photons. Firstly, we present a symmetry detector which is capable of analyzing twin-beam six-photon symmetric states in the regime of weak nonlinearities. By cascading symmetry detectors, then, it is shown that one can generate third-order PDC photons from a class of twin-beam six-photon symmetric states. Finally, as an example, we describe an application of third-order PDC photons for exploring six-mode-photon entangled states with linear optics.
Plasma defocusing in dual-pulse laser ignition
Authors: Tropina Albina A , Pokharel Sagar , New-Tolley Matthew R , Shneider Mikhail N
Published: February 2021

The paper presents simulation results of hydrogen-air mixture ignition by an ultraviolet followed by a near-infrared laser pulse. We used the three-temperature plasma model in a combination with the beam propagation method. Effect of plasma defocusing on the ignition kernel development is reported. It is shown that the plasma generated by the pre-ionizing pulse affects the position of the focal region of the second heating pulse with resulting changes in the distribution of the laser energy absorption, electron and radical production and ignition kernel dynamics. For the case with the defocusing effect we observed a shift of the peaks of translational and vibrational temperatures towards the direction of the laser pulse and two peaks on the axial profile of the electron temperature, reflecting local changes both in Joule heating and electron energy losses.
Coercivity analysis of cubic and tetragonal (Cu,Co) ferrite particles within the global model
Authors: Latiff Hawa , Eslava Gabriel Gomez , Devillers Thibaut , Yanagihara Hideto , Dempsey Nora M , Givord Dominique
Published: February 2021

We analyzed the coercivity of both cubic and tetragonally distorted Co
x
Cu1−x
Fe2O4 particles (x = 0.2 and 0.1, respectively) using the global model. According to magnetic viscosity measurements, the size of the activation volumes v
a increases from around 2000 nm3 (v
a
1/3 ≈ 13 nm) at 10 K for both samples, to close to 175 000 nm3 for the cubic sample and 5400 nm3 for the tetragonally distorted sample at 300 K. The microstructure-related phenomenological parameters obtained from the global model analysis are α= 0.29 and N
eff = −0.01 and α= 0.39 and N
eff = −0.24 for the cubic and tetragonal samples, respectively. High-resolution transmission electron microscopy images of the tetragonal sample showed that nanograins are connected through a thin amorphous layer (∼1 nm), which could account for the intergranular exchange interactions indicated by the negative value of N
eff as well as values of M
r/M
s > 0.5 for such isotropic samples. Low temperature discrepancies are tentatively attributed to magnetic reversal being governed by a local heating process following thermal activation.
Data augmentation for rolling bearing fault diagnosis using an enhanced few-shot Wasserstein auto-encoder with meta-learning
Authors: Pei Zeyu , Jiang Hongkai , Li Xingqiu , Zhang Jianjun , Liu Shaowei
Published: February 2021

Despite the advance of intelligent fault diagnosis for rolling bearings, in industries, data-driven methods still suffer from data acquisition and imbalance. We propose an enhanced few-shot Wasserstein auto-encoder (fs-WAE) to reverse the negative effect of imbalance. Firstly, an enhanced WAE is proposed for data augmentation, in which squeeze-and-excitation blocks are applied to calibrate channel-wise feature responses adaptively, strengthening the representational power of encoder. Secondly, a meta-learning strategy called Reptile is utilized to further enhance the mapping ability of WAE from prior distribution to vibration signals in the face of small dataset. Finally, gradient penalty is introduced as a regularization term to provide a flexible optimization function. The proposed method is applied to the pattern recognition based on experimental and engineering datasets. Moreover, comparative results demonstrate the utility and superiority of fs-WAE over other models in terms of efficiency and the resilience to imbalance degree.