bluuebunny/crossref_metadata_2025 huggingface dataset:
Cryogenic microwave loss in epitaxial Al/GaAs/Al trilayers for superconducting circuits
Authors: McRae C. R. H. , McFadden A. , Zhao R. , Wang H. , Long J. L. , Zhao T. , Park S. , Bal M. , Palmstrøm C. J. , Pappas D. P.
Published: January 2021

Epitaxially grown superconductor/dielectric/superconductor trilayers have the potential to form high-performance superconducting quantum devices and may even allow scalable superconducting quantum computing with low-surface-area qubits such as the merged-element transmon. In this work, we measure the power-independent loss and two-level-state (TLS) loss of epitaxial, wafer-bonded, and substrate-removed Al/GaAs/Al trilayers by measuring lumped element superconducting microwave resonators at millikelvin temperatures and down to single-photon powers. The power-independent loss of the device is (4.8±0.1)×10−5, and the resonator-induced intrinsic TLS loss is (6.4±0.2)×10−5. Dielectric loss extraction is used to determine a lower bound of the intrinsic TLS loss of the trilayer of 7.2×10−5. The unusually high power-independent loss is attributed to GaAs’s intrinsic piezoelectricity.
Natural shear wave imaging using vocal tract vibrations: Introducing vocal passive elastography (V-PE) to thyroid elasticity mapping
Authors: Beuve Steve , Callé Samuel , Khoury Elise , Simon Emmanuel Gilles , Remenieras Jean-Pierre
Published: January 2021

We present a shear wave elastography (SWE) approach for thyroid characterization that is inspired by passive elastography, which extracts elasticity from the natural vibrations in living tissues that are caused by cardiac motion, blood pulsatility, and muscle activity. On thyroid, this physiological noise is mainly due to the carotid pulsation, which is in the 1–10 Hz bandwidth and is located right next to the gland. In order to decrease the shear wavelength and increase the signal to noise ratio, we propose to create in the thyroid a complex shear wave field by using natural vocal tract vibrations. The nature of the sound can be easily modified to be narrow or broad band, with small or large amplitude. Using correlation-based algorithm and a sound sustained at 150 Hz, we have developed an innovative technique using ultrasound, allowing us to compute a 2D shear wave velocity map, superposed onto a B-mode ultrasound image of a volunteer's thyroid. Using our vocal passive elastography method, shear wave velocity was measured at every point within a mask surrounding the thyroid with a pixel resolution of 150 × 150 μm2. The mean shear wave speed value measured is 3.2 m/s, taking its value from 0.7 m/s to 8.8 m/s. The values obtained were in good agreement with comparative shear wave elastography (SWE) measurements.
Orientation control of optical mode ferromagnetic resonance: From uniaxial to omni-directional
Authors: Huang Yicong , Zhang Shouheng , Sang Tao , Zhao Guoxia , Jin Zhejun , Zong Weihua , Wang Xia , Xu Jie , Cao Derang , Miao Guo-Xing , Li Shandong
Published: January 2021

Both high ferromagnetic resonance frequency (fr) and homogeneous angular performance are important for soft magnetic films to be used in high-frequency integrated circuit devices. However, high fr are obtainable only along the easy axis direction of the magnetic anisotropic materials. In uniaxially anisotropic FeCoB/Ru/FeCoB films, we could obtain an ultrahigh optical mode ferromagnetic resonance frequency (frO) up to 19.16 GHz along the easy axis under a self-bias field due to the enhancement from strong interlayer exchange coupling. However, the uniaxial intensity distribution of optical mode resonance seriously hinders the practical application in microwave components. In order to obtain the desired homogeneous angular performance, soft magnetic films with widely distributed magnetic anisotropy directions in the films were prepared and a nearly omni-directional frO with uniform values around 13.5 GHz was achieved. This study demonstrates that controlling the magnetic anisotropy's angular distribution is an effective way to obtain isotropic, self-bias magnetic films with ultrahigh fr.
Domain structure transition in compressively strained (100)/(001) epitaxial tetragonal PZT film
Authors: Ichinose Daichi , Shimizu Takao , Sakata Osami , Yamada Tomoaki , Ehara Yoshitaka , Funakubo Hiroshi
Published: January 2021

A 30-nm-thick epitaxial tetragonal (100)/(001) Pb(Zr0.22Ti0.78)O3 (PZT) thin film was grown at 600 °C on (001) KTaO3 (KTO) single-crystal substrate by metalorganic chemical vapor deposition. The a/c domain structure in the PZT film was analyzed in detail at room temperature by synchrotron x-ray diffraction (XRD) and piezoresponse force microscopy techniques. The temperature dependence of the crystal structure was investigated by XRD reciprocal space mapping and in-plane grazing incidence XRD. The PZT films were grown on KTO substrates under compressive strains from 700 °C to room temperature. This compressive strain gave rise to a perfect (001) orientation below a Curie temperature (TC) of ∼520 °C. An in-plane a-axis lattice parameter for the c domain kept the same value as that of the substrate lattice up to 350 °C despite the ferroelectric transition. Nucleation of the a domain started at around 350 °C. The formation of the a domain released the strain for the in-plane a-axis lattice parameter, as confirmed by in-plane analysis of the crystal structure. The results revealed that the in-plane average surface area of the PZT unit cell continued to match that of the KTaO3 substrate from 700 °C to room temperature, regardless of the domain structure evolution.
Efficient implementation of isotropic cubic response functions for two-photon absorption cross sections within the self-consistent field approximation
Authors: Ahmadzadeh Karan , Scott Mikael , Brand Manuel , Vahtras Olav , Li Xin , Rinkevicius Zilvinas , Norman Patrick
Published: January 2021

Within the self-consistent field approximation, computationally tractable expressions for the isotropic second-order hyperpolarizability have been derived and implemented for the calculation of two-photon absorption cross sections. The novel tensor average formulation presented in this work allows for the evaluation of isotropic damped cubic response functions using only ∼3.3% (one-photon off-resonance regions) and ∼10% (one-photon resonance regions) of the number of auxiliary Fock matrices required when explicitly calculating all the needed individual tensor components. Numerical examples of the two-photon absorption cross section in the one-photon off-resonance and resonance regions are provided for alanine–tryptophan and 2,5-dibromo-1,4-bis(2-(4-diphenylaminophenyl)vinyl)-benzene. Furthermore, a benchmark set of 22 additional small- and medium-sized organic molecules is considered. In all these calculations, a quantitative assessment is made of the reduced and approximate forms of the cubic response function in the one-photon off-resonance regions and results demonstrate a relative error of less than ∼5% when using the reduced expression as compared to the full form of the isotropic cubic response function.
Ionic thermoelectric materials for near ambient temperature energy harvesting
Authors: Liu Weishu , Qian Xin , Han Cheng-Gong , Li Qikai , Chen Gang
Published: January 2021

Ionic thermoelectric (i-TE) materials, using ions as the energy carrier, can generate a voltage under a temperature difference, bearing similarities to the Seebeck effect of electrons and holes in solid-state materials. Recent experiments have demonstrated large thermopower of quasi-solid-state i-TE materials, which are attractive for harvesting ambient heat as large enough voltage can be generated under a small temperature difference to match the voltage input needs of sensors for internet-of-things applications. In this perspective article, we discuss similarities and differences of i-TE materials from electronic-based thermoelectric materials and also different i-TE thermoelectric effects including the thermodiffusion (Soret) effect and the thermogalvanic effect, in which the latter includes redox reaction entropy and the Soret effect. Strategies to improve performances of materials and devices are elaborated, together with needs for future research in understanding microscopic origins of different effects.
Computational discovery of stable phases of graphene and h-BN van der Waals heterostructures composed of group III–V binary compounds
Authors: Akiyama Toru , Kawamura Takahiro , Ito Tomonori
Published: January 2021

We propose stable structures of graphene and hexagonal BN (h-BN) van der Waals (vdW) heterostructures in conjunction with conventional group III–V binary compounds on the basis of density functional calculations. The calculations demonstrate that the binary compounds in graphene and h-BN superlattices are stabilized by forming the double-layer honeycomb (DLHC) structure, different from its stable structure in the bulk phase. Due to peculiar electronic structures of group III–V binary compounds in the DLHC structure, various types of electronic properties are obtained depending on the combination of two-dimensional materials (graphene and h-BN) and group III–V binary compounds. The calculated results suggest that diverse combinations and exotic electronic properties could be tailored in vdW heterostructures including group III–V compounds.
The 2D Debye length: An analytical study of weak charge screening in 2D semiconductors
Authors: Bechhofer Adina R. , Ueda Akiko , Nipane Ankur , Teherani James T.
Published: January 2021

Simple perturbations (such as a line charge or a sheet charge) in 2D semiconducting materials create difficult solutions to the Poisson equation due to the non-uniform out-of-plane electric fields that result from the perturbative charge. Here, for the first time, we determine simple and general analytical expressions for the potential profile, its Fourier representation, the corresponding 2D Debye screening length, and the charge screening behavior in 2D semiconductors due to a line charge perturbation. In contrast to conventional 3D semiconductors, we find that the 2D Debye length goes as 1/ND,2D, where ND,2D is the 2D semiconductor doping density, and this leads to markedly different Debye lengths as compared to those determined by the conventional (3D) Debye length expression. We show that the potential profile due to a charge perturbation in a 2D semiconductor does not decay exponentially with distance from the perturbation (as is the case for 3D semiconductors) but instead decays logarithmically in the immediate vicinity of the perturbation and as 1/x2 when the distance is approximately equal to or greater than the 2D Debye length. Overall, this work establishes an analytical approach for determining a fundamental electrostatic parameter for 2D semiconductors.
Experimental study of the effects of a viscous liquid layer on the cavity dynamics of vertical entry by a sphere into water at low Froude number
Authors: Sun Tiezhi , Wang Heng , Shi Chongbin , Zong Zhi , Zhang Guiyong
Published: January 2021

The water entry process is relevant to a wide range of engineering applications and has been extensively investigated. Most liquids used in such studies are single-layered, and little attention has been paid to how the structure of a two-layer liquid system affects the splash and cavity formation. In this study, we use high-speed photography to experimentally investigate the water entry of a sphere after it has passed vertically through a layer of highly viscous liquid (dimethicone) at a low Froude number. We investigate the effects of different thicknesses of this dimethicone layer and find that the formation of the splash crown is closely related to both the thickness and the Froude number. In a certain range of dimethicone thickness, the height of the splash interface decreases with the increasing thickness and increases with the decreasing Froude number. The dimensionless interface height at the pinch-off time is found to have a linear relationship with the dimensionless initial velocity of the sphere. Furthermore, the formation of the cavity, including its length and pinch-off depth, depends on the Froude number. However, the pinch-off time is almost independent of the dimethicone thickness and the Froude number, and the cavity length is nearly independent of the dimethicone thickness for all Froude numbers examined.
Dynamic multiple nanoparticle trapping using metamaterial plasmonic tweezers
Authors: Kotsifaki Domna G. , Truong Viet Giang , Nic Chormaic Síle
Published: January 2021

Optical manipulation has attracted remarkable interest owing to its versatile and noninvasive nature. However, conventional optical trapping remains inefficient in the nanoscopic world. The emergence of plasmonics in recent years has brought a revolutionary change in overcoming limitations due to diffraction and the requirements for high trapping laser powers. Among the near-field optical trapping cavity-based systems, Fano-resonant optical tweezers have a robust trapping capability. In this work, we experimentally demonstrate sequential trapping of 20 nm particles through the use of metamaterial plasmonic optical tweezers. We investigate the multiple trapping via trap stiffness measurements for various trapping configurations at low and high incident laser intensities. Our plasmonic configuration could be used as a light-driven nanoscale sorting device under low laser excitation. Our results provide an alternative approach to trap multiple nanoparticles at distinct hotspots, enabling ways to control mass transport on the nanoscale.
Suppressed oxidation of tin perovskite by Catechin for eco-friendly indoor photovoltaics
Authors: Yang Wen-Fan , Cao Jun-Jie , Dong Chong , Li Meng , Tian Qi-Sheng , Wang Zhao-Kui , Liao Liang-Sheng
Published: January 2021

While fabricating tin (Sn)-based perovskite solar cells (PSCs), it is beneficial to tune the bandgap of the perovskite absorber layer by changing the ratio of halide ions, for improved performance. However, oxidation limits the power conversion efficiency (PCE) [Jeon et al., Nat. Mater. 13, 897 (2014); Ke et al., ACS Energy Lett. 3, 1470 (2018); Yang et al., Adv. Energy Mater. 10, 1902584 (2020); Baig et al., Optik 170, 463 (2018)]. Herein, we introduced Catechin into the perovskite layer to suppress oxidation. We achieved FA0.75MA0.25SnI2Br thin films with a low Sn4+ ratio. Owing to Catechin doping, devices yielded an average PCE of 5.45% and a Champion PCE of 6.02%, higher than the average PCE of 4.29% for the device without Catechin doping. Furthermore, the stability of the doped device improved. It also exhibited dramatic performance when exposed to indoor lighting with the maximum PCE approaching 12.81% under 1000 lx. This work further advances the field of lead-free PSCs and the potential of indoor photovoltaics.
Energy dissipation during two-state switching for quantum-dot cellular automata
Authors: Pidaparthi Subhash S. , Lent Craig S.
Published: January 2021

We examine the energy dissipated by a two-state quantum system during a switching operation when interacting with a thermal environment. For an isolated system, the excess energy decreases exponentially with switching time. For classically damped systems, the energy dissipation decreases linearly with switching time. We model the quantum system coupled to a thermal environment using a Lindblad equation for the density matrix. For rapid switching, the exponential quantum adiabaticity holds. For slow enough switching, the damping from the bath yields linear dissipation, as in the classical limit. Between these two limits, when the switching time is comparable to the characteristic energy transfer time to the thermal bath, there is an inverted region when dissipation increases with longer switching times. Consequences for the design of molecular quantum-dot cellular automata are discussed.
Supercollisions of fast H-atom with ethylene on an accurate full-dimensional potential energy surface
Authors: Fu Yan-Lin , Lu Xiaoxiao , Han Yong-Chang , Fu Bina , Zhang Dong H.
Published: January 2021

The collisions transferring large portions of energy are often called supercollisions. In the H + C2H2 reactive system, the rovibrationally cold C2H2 molecule can be activated with substantial internal excitations by its collision with a translationally hot H atom. It is interesting to investigate the mechanisms of collisional energy transfer in other important reactions of H with hydrocarbons. Here, an accurate, global, full-dimensional potential energy surface (PES) of H + C2H4 was constructed by the fundamental invariant neural network fitting based on roughly 100 000 UCCSD(T)-F12a/aug-cc-pVTZ data points. Extensive quasi-classical trajectory calculations were carried out on the full-dimensional PES to investigate the energy transfer process in collisions of the translationally hot H atoms with C2H4 in a wide range of collision energies. The computed function of the energy-transfer probability is not a simple exponential decay function but exhibits large magnitudes in the region of a large amount of energy transfer, indicating the signature of supercollisions. The supercollisions among non-complex-forming nonreactive (prompt) trajectories are frustrated complex-forming processes in which the incoming H atom penetrates into C2H4 with a small C–H distance but promptly and directly leaves C2H4. The complex-forming supercollisions, in which either the attacking H atom leaves (complex-forming nonreactive collisions) or one of the original H atoms of C2H4 leaves (complex-forming reactive trajectories), dominate large energy transfer from the translational energy to internal excitation of molecule. The current work sheds valuable light on the energy transfer of this important reaction in the combustion and may motivate related experimental investigations.
Sensing non-light-absorbing media via thermally modulated photoacoustic measurements
Authors: Ding Wenzheng , Ji Zhong , Liu Chengyi , Duan Rui
Published: January 2021

In conventional photoacoustic (PA) imaging, the imaging contrast is largely determined by the difference in optical absorption of the targets. Therefore, to distinguish non-light-absorbing media using these optical methods presents practical difficulties. It has been shown that the difference in thermodynamic properties is more obvious in certain situations. Further, it has been found experimentally that the PA response of a probe is significantly different due to the thermodynamic action of the surrounding medium, for example, there is a reverse trend for lipid and collagen. In this Letter, an optical method using a PA-responsive external probe to sense the difference in thermodynamic properties of non-light-absorbing media is proposed. The experimental results demonstrate that the proposed method provides a scheme to solve the challenges encountered by traditional PA technologies and has significant potential in biomedical applications.
Modulation of acoustic self-accelerating beams with tunable curved metasurfaces
Authors: Li Xiao-Shuang , Zhou Hong-Tao , Wang Yan-Feng , Wang Yue-Sheng
Published: January 2021

Self-accelerating beams have applications in optic and acoustic fields due to their peculiar properties. As a promising artificial two-dimensional metamaterial, a metasurface can be used as the generator of self-accelerating beams. However, restricted by the generalized Snell's law, most research hotspots focus on flat metasurfaces. In this Letter, the generalized Snell's law on an arbitrary curved reflective surface is discussed. Then, the phase profile for the self-accelerating beams generated from the curved reflective surface is derived based on the caustic theory. The metasurface consisting of the tunable spiral path units is constructed, and numerical and experimental validations are performed. The methodology developed in the present letter extends the applications of the self-accelerating beams.
n-type GaN surface etched green light-emitting diode to reduce non-radiative recombination centers
Authors: Han Dong-Pyo , Fujiki Ryoto , Takahashi Ryo , Ueshima Yusuke , Ueda Shintaro , Lu Weifang , Iwaya Motoaki , Takeuchi Tetsuya , Kamiyama Satoshi , Akasaki Isamu
Published: January 2021

In this study, we attempt to identify the presence of surface defects (SDs) at an n-type GaN surface after high-temperature growth and gain insight into their intrinsic features. To this end, first, we carefully investigate n-type GaN samples with different surface etching depths. Low-temperature photoluminescence (PL) spectra reveal that SDs are most likely nitrogen vacancies (VN) and/or VN-related point defects intensively distributed within ∼100 nm from the n-type GaN surface after a high-temperature growth. We investigate the effect of SDs on the internal quantum efficiency (IQE) of green light-emitting diodes (LEDs) by preparing GaInN-based green LEDs employing a surface-etched n-type GaN, which exhibits a prominent enhancement of the PL efficiency with an increase in the etching depth. This effect is attributable to the reduced non-radiative recombination centers in multiple-quantum-well active regions because the SDs near the n-type GaN surface are removed by etching. We discuss strategies of in situ engineering on SDs to further improve the IQE in GaInN-based green LEDs on the basis of the results presented in this study.
Spin–orbit torque-induced magnetization switching in Pt/Co–Tb/Ta structures
Authors: Wu Yunzhuo , Zeng Xiaoxue , Guo Yonghai , Jia Qi , Wang Bo , Cao Jiangwei
Published: January 2021

Although transition metal (TM)-rare earth (RE) alloy film has potential application as an information storage medium in spintronic devices, study of the physical mechanism and microscopic process for the current-induced magnetization switching by spin–orbit torque (SOT) in TM-RE is still inadequate. In this work, we investigated the SOT effect and its driven magnetization switching in Pt/Co–Tb/Ta structures with various Co–Tb compositions. The results show that the current-induced SOT effective fields follow 1/Ms law near the compensation composition in this structure. Because of the large SOT effective field and the low coercivity for the Co–Tb layer near the compensation composition, the current-induced magnetization switching with a threshold current density as low as 1010 A/m2 was achieved in the system. The direct Kerr imaging on the switching process verifies two different current-induced switching mechanisms in the Pt/Co–Tb/Ta system.
Arbitrary flow boundary conditions in smoothed dissipative particle dynamics: A generalized virtual rheometer
Authors: Moreno N. , Ellero M.
Published: January 2021

In this work, a methodology to perform rheological studies on smoothed dissipative particle dynamics under arbitrary flow configurations is introduced. To evaluate the accuracy and flexibility of the proposed methodology, viscometric studies for Newtonian fluids under pure shear, pure extension, and arbitrary flows in bulk or near walls are introduced. The applicability of this methodology to obtain viscoelastic properties of non-Newtonian fluids, such as polymer solutions, is also presented. The new computational approach offers relevant advantages in a variety of applications ranging from multiscale simulations to the rheological characterization of complex flows.
Controlling the direction of topological transport in a non-Hermitian time-reversal symmetric Floquet ladder
Authors: Höckendorf B. , Alvermann A. , Fehske H.
Published: January 2021

We propose a one-dimensional Floquet ladder that possesses two distinct topological transport channels with opposite directionality. The transport channels occur due to a Z2 non-Hermitian Floquet topological phase that is protected by time-reversal symmetry. The signatures of this phase are two pairs of Kramers degenerate Floquet quasienergy bands that are separated by an imaginary gap. We discuss how the Floquet ladder can be implemented in a photonic waveguide lattice and show that the direction of transport in the resulting waveguide structure can be externally controlled by focusing two light beams into adjacent waveguides. The relative phase between the two light beams selects which of the two transport channels is predominantly populated, while the angles of incidence of the two light beams determine which of the transport channels is suppressed by non-Hermitian losses. We identify the optimal lattice parameters for the external control of transport and demonstrate the robustness of this mechanism against disorder.
Orientational decoherence within molecules and emergence of the molecular shape
Authors: Mátyus Edit , Cassam-Chenaï Patrick
Published: January 2021

The question of classicality is addressed in relation with the shape of the nuclear skeleton of molecular systems. As the most natural environment, the electrons of the molecule are considered as continuously monitoring agents for the nuclei. For this picture, an elementary formalism of decoherence theory is developed and numerical results are presented for few-particle systems. The numerical examples suggest that the electron–nucleus Coulomb interaction is sufficient for inducing a blurred shape with strong quantum coherences in compounds of the lightest elements, H2, D2, T2, and HeH+.
Experimental and theoretical studies on the surface morphology variation of a Ni substrate by graphene growth
Authors: Takahashi Junro , Ueyama Tomoyuki , Kamei Kazuhito , Kato Hiroki , Homma Yoshikazu
Published: January 2021

As graphene grows on a metal substrate, step bunching and terrace formation occur due to thermodynamic instability. Variation in the terrace–step bunching morphology is caused by graphene–metal interaction. The mechanism for this morphological variation was elucidated in terms of the crystal lattice matching by the observation of step bunching formation using in situ scanning electron microscopy and analysis of the crystal orientation of the same microscopic field using electron backscatter diffraction. The cross-sectional structure was also observed using transmission electron microscopy (TEM). These combined methods enable a reliable analysis of the step bunching region. The lattice matching was also evaluated according to the 0-lattice theory. From the structural analysis using TEM and the application of the 0-lattice theory, the graphene-covered surface was confirmed to consist of good and poor lattice-matching regions. The steps ejected from the terrace region piled up in the poor lattice-matching region to form a low Miller index plane. It was concluded that step flow occurs on the good lattice-matching region and steps are piled up and arranged very closely on the poor matching region based on the lattice-matching evaluation by the 0-lattice theory.
Magnon relaxation time in ferromagnetic Cr2Ge2Te6 monolayer governed by magnon-phonon interaction
Authors: Wang Ke , Xu Xiansong , Cheng Yuan , Zhang Min , Wang Jian-Sheng , Wang Hai , Zhang Gang
Published: January 2021

Recently, bulk and multi-layer Cr2Ge2Te6 (CGT) has garnered much attention because of its interesting physical properties and promising technological aspects, including information storage and spintronic application. Here, using density functional theory calculations, we investigate the spin-wave spectrum and magnon-phonon interaction (MPI) in the CGT monolayer. The strength of MPI and the magnon relaxation time are estimated by the broadening in the spin-wave spectrum. We find that the MPI in the CGT monolayer exhibits weak in-plane isotropy and a strong wave vector dependence. The broadening of optical magnons is constant near the center of the Brillouin zone, while that for acoustic magnons shows a quadratic wave-vector dependence. Moreover, this wave-vector dependence is independent of temperature. As the temperature increases from 5 K to 55 K, the magnon relaxation time decreases 4 times, revealing the importance of MPI in spin dynamics of the ferromagnetic CGT monolayer. Our work provides an in-depth understanding of the magnon-phonon interaction in the ferromagnetic Cr2Ge2Te6 monolayer.
Electric field-induced gas dissolving in aqueous solutions
Authors: Xie Zhang , Li Zheng , Li Jingyuan , Kou Jianlong , Yao Jun , Fan Jintu
Published: January 2021

Gas dissolution or accumulation regulating in an aqueous environment is important but difficult in various fields. Here, we performed all-atom molecular dynamics simulations to study the dissolution/accumulation of gas molecules in aqueous solutions. It was found that the distribution of gas molecules at the solid–water interface is regulated by the direction of the external electric field. Gas molecules attach and accumulate to the interface with an electric field parallel to the interface, while the gas molecules depart and dissolve into the aqueous solutions with a vertical electric field. The above phenomena can be attributed to the redistribution of water molecules as a result of the change of hydrogen bonds of water molecules at the interface as affected by the electric field. This finding reveals a new mechanism of regulating gas accumulation and dissolution in aqueous solutions and can have tremendous applications in the synthesis of drugs, the design of microfluidic device, and the extraction of natural gas.
In silico design of a new Zn–triazole based metal–organic framework for CO2 and H2O adsorption
Authors: Dahmani R. , Grubišić S. , Djordjević I. , Ben Yaghlane S. , Boughdiri S. , Chambaud G. , Hochlaf M.
Published: January 2021

In search for future good adsorbents for CO2 capture, a nitrogen-rich triazole-type Metal–Organic Framework (MOF) is proposed based on the rational design and theoretical molecular simulations. The structure of the proposed MOF, named Zinc Triazolate based Framework (ZTF), is obtained by replacing the amine-organic linker of MAF-66 by a triazole, and its structural parameters are deduced. We used grand-canonical Monte Carlo (GCMC) simulations based on generic classical force fields to correctly predict the adsorption isotherms of CO2 and H2O. For water adsorption in MAF-66 and ZTF, simulations revealed that the strong hydrogen bonding interactions of water with the N atoms of triazole rings of the frameworks are the main driving forces for the high adsorption uptake of water. We also show that the proposed ZTF porous material exhibits exceptional high CO2 uptake capacity at low pressure, better than MAF-66. Moreover, the nature of the interactions between CO2 and the MAF-66 and ZTF surface cavities was examined at the microscopic level. Computations show that the interactions occur at two different sites, consisting of Lewis acid–Lewis base interactions and hydrogen bonding, together with obvious electrostatic interactions. In addition, we investigated the influence of the presence of H2O molecules on the CO2 adsorption on the ZTF MOF. GCMC simulations reveal that the addition of H2O molecules leads to an enhancement of the CO2 adsorption at very low pressures but a reduction of this CO2 adsorption at higher pressures.
High Mg activation in implanted GaN by high temperature and ultrahigh pressure annealing
Authors: Breckenridge M. Hayden , Tweedie James , Reddy Pramod , Guan Yan , Bagheri Pegah , Szymanski Dennis , Mita Seiji , Sierakowski Kacper , Boćkowski Michał , Collazo Ramon , Sitar Zlatko
Published: January 2021

We demonstrate high p-type conductivity and hole concentrations >1018 cm−3 in Mg-implanted GaN. The implantation was performed at room temperature and by post-implantation annealing at 1 GPa of N2 and in a temperature range of 1200–1400 °C. The high pressure thermodynamically stabilized the GaN surface without the need of a capping layer. We introduce a “diffusion budget,” related to the diffusion length, as a convenient engineering parameter for comparing samples annealed at different temperatures and for different times. Although damage recovery, as measured by XRD, was achieved at relatively low diffusion budgets, these samples did not show p-type conductivity. Further analyses showed heavy compensation by the implantation-induced defects. Higher diffusion budgets resulted in a low Mg ionization energy (∼115 meV) and almost complete Mg activation. For even higher diffusion budgets, we observed significant loss of Mg to the surface and a commensurate reduction in the hole conductivity. High compensation at low diffusion budgets and loss of Mg at high diffusion budgets present a unique challenge for shallow implants. A direct control of the formation of compensating defects arising from the implantation damage may be necessary to achieve both hole conductivity and low Mg diffusion.
The decline of butterflies in Europe: Problems, significance, and possible solutions
Authors: Warren Martin S. , Maes Dirk , van Swaay Chris A. M. , Goffart Philippe , Van Dyck Hans , Bourn Nigel A. D. , Wynhoff Irma , Hoare Dan , Ellis Sam
Published: January 2021

We review changes in the status of butterflies in Europe, focusing on long-running population data available for the United Kingdom, the Netherlands, and Belgium, based on standardized monitoring transects. In the United Kingdom, 8% of resident species have become extinct, and since 1976 overall numbers declined by around 50%. In the Netherlands, 20% of species have become extinct, and since 1990 overall numbers in the country declined by 50%. Distribution trends showed that butterfly distributions began decreasing long ago, and between 1890 and 1940, distributions declined by 80%. In Flanders (Belgium), 20 butterflies have become extinct (29%), and between 1992 and 2007 overall numbers declined by around 30%. A European Grassland Butterfly Indicator from 16 European countries shows there has been a 39% decline of grassland butterflies since 1990. The 2010 Red List of European butterflies listed 38 of the 482 European species (8%) as threatened and 44 species (10%) as near threatened (note that 47 species were not assessed). A country level analysis indicates that the average Red List rating is highest in central and mid-Western Europe and lowest in the far north of Europe and around the Mediterranean. The causes of the decline of butterflies are thought to be similar in most countries, mainly habitat loss and degradation and chemical pollution. Climate change is allowing many species to spread northward while bringing new threats to susceptible species. We describe examples of possible conservation solutions and a summary of policy changes needed to conserve butterflies and other insects.
Insect biomass decline scaled to species diversity: General patterns derived from a hoverfly community
Authors: Hallmann Caspar A. , Ssymank Axel , Sorg Martin , de Kroon Hans , Jongejans Eelke
Published: January 2021

Significance

Various sources have reported insect decline in total biomass, numbers, and species diversity. With German data on a species-rich hoverfly community over 25 y and a theoretical model, we show how these decline rates are interrelated. The relationship between biomass and diversity losses depends on whether common or rarer species are most affected. Our analyses show stronger declines of common than rare hoverfly species. Strong reductions (up to −80%) in total abundance and biomass correspond with observed species richness declines of −20% to −40% on a seasonal basis. On a daily basis, however, hoverfly diversity declined in proportion to biomass loss, with important consequences for the functioning of ecosystems.
High-speed compressed-sensing fluorescence lifetime imaging microscopy of live cells
Authors: Ma Yayao , Lee Youngjae , Best-Popescu Catherine , Gao Liang
Published: January 2021

Significance

This paper describes a high-speed fluorescence lifetime imaging method, compressed-sensing fluorescence lifetime imaging microscopy (compressed FLIM), which can produce high-resolution two-dimensional (2D) lifetime images at an unprecedented frame rate. Compared to other state-of-the-art FLIM imagers, compressed FLIM has a striking advantage in acquiring a widefield lifetime image within a single camera snapshot, thereby eliminating motion artifacts and enabling fast recording of biological events.
Time-reversal symmetry breaking in the Fe-chalcogenide superconductors
Authors: Zaki Nader , Gu Genda , Tsvelik Alexei , Wu Congjun , Johnson Peter D.
Published: January 2021

Significance

In the Fe-chalcogenide superconductors, topology, superconductivity, and magnetism all come together to provide a platform for a range of exotic quantum phenomena. Topology and superconductivity can interact to give topological superconductivity capable of supporting Majorana fermions that could prove to be the basis of future qubit technology. The large spin–orbit interaction associated with the topological phenomena combined with magnetism can potentially result in the quantum anomalous Hall effect although the superconductivity will work against such. It is important that we understand the relevant roles of the different phenomena. Here we provide evidence of time-reversal symmetry breaking and associated mass acquisition in a topological surface state at the superconducting transition, an observation highly suggestive of the formation of surface ferromagnetism.
Global mapping of urban–rural catchment areas reveals unequal access to services
Authors: Cattaneo Andrea , Nelson Andrew , McMenomy Theresa
Published: January 2021

Significance

Physical access to services and employment opportunities shapes the lives of people everywhere. For 3.4 billion people living in rural locations, the size of nearby urban centers and the associated travel time affect the breadth of services and opportunities available and their accessibility. We identify catchment areas of urban centers of different sizes and how many people gravitate toward each city or town, providing a full spatial representation of the connection between rural areas and urban centers and fresh insights on the diversity of urban–rural systems. The global dataset opens the door to applied research in various disciplines—such as poverty reduction, food systems, health, and education—where a person’s place of residence is an important factor.
Interplay between desmoglein2 and hypoxia controls metastasis in breast cancer
Authors: Chang Po-Hao , Chen Min-Che , Tsai Ya-Ping , Tan Grace Y. T. , Hsu Pang-Hung , Jeng Yung-Ming , Tsai Yi-Fang , Yang Muh-Hwa , Hwang-Verslues Wendy W.
Published: January 2021

Significance

During metastasis, hypoxia is a major force driving primary tumor cells to disseminate into the circulatory system. The key factors that promote circulating tumor cells (CTC) dissemination and allow them to successfully colonize distal sites are still incompletely known. We found that down-regulation of DSG2 in hypoxic tumor allowed single tumor cell dissemination, while DSG2-expressing tumors generated more CTC clusters. Reinduction of DSG2 expression in single CTCs may contribute to CTC survival and colonization in distant organs. These findings highlight the importance of DSG2 in breast cancer progression and metastasis.
Topological metals and finite-momentum superconductors
Authors: Yuan Noah F. Q. , Fu Liang
Published: January 2021

Significance

Our work uncovers an interesting connection between topological band theory and superconductivity. While BCS superconductivity at zero magnetic field is largely insensitive to electron wavefunction, in this work we reveal a rich phase diagram of finite-momentum superconductivity in the presence of spin–orbit splitting and Zeeman fields, where electron pairing depends closely on the topology of spin texture on the Fermi surface.
Invariant timescale hierarchy across the cortical somatosensory network
Authors: Rossi-Pool Román , Zainos Antonio , Alvarez Manuel , Parra Sergio , Zizumbo Jerónimo , Romo Ranulfo
Published: January 2021

The ability of cortical networks to integrate information from different sources is essential for cognitive processes. On one hand, sensory areas exhibit fast dynamics often phase-locked to stimulation; on the other hand, frontal lobe areas with slow response latencies to stimuli must integrate and maintain information for longer periods. Thus, cortical areas may require different timescales depending on their functional role. Studying the cortical somatosensory network while monkeys discriminated between two vibrotactile stimulus patterns, we found that a hierarchical order could be established across cortical areas based on their intrinsic timescales. Further, even though subareas (areas 3b, 1, and 2) of the primary somatosensory (S1) cortex exhibit analogous firing rate responses, a clear differentiation was observed in their timescales. Importantly, we observed that this inherent timescale hierarchy was invariant between task contexts (demanding vs. nondemanding). Even if task context severely affected neural coding in cortical areas downstream to S1, their timescales remained unaffected. Moreover, we found that these time constants were invariant across neurons with different latencies or coding. Although neurons had completely different dynamics, they all exhibited comparable timescales within each cortical area. Our results suggest that this measure is demonstrative of an inherent characteristic of each cortical area, is not a dynamical feature of individual neurons, and does not depend on task demands.
Imaging conical intersection dynamics during azobenzene photoisomerization by ultrafast X-ray diffraction
Authors: Keefer Daniel , Aleotti Flavia , Rouxel Jérémy R. , Segatta Francesco , Gu Bing , Nenov Artur , Garavelli Marco , Mukamel Shaul
Published: January 2021

Significance

Vibronic coherences are unique features that emerge in the decisive moments of photochemistry and photophysics. Here we demonstrate how X-ray diffraction can access fundamental information about these coherences. This is enabled by recent developments at free-electron lasers, working toward temporal resolution and single-molecule accessibility of scattering-based measurements. Time-resolved diffraction patterns of the isomerization of azobenzene are simulated. The process is monitored in time via the momentum-space signal, with a special focus on the mixed elastic/inelastic scattering from coherences. We give practical ideas on how this relatively weak contribution to the signal can potentially be retrieved. A direct connection to the real-space movie of the conical intersection dynamics is made, enabling the observation of quantum coherences that direct chemical processes.
Regulation of a subset of release-ready vesicles by the presynaptic protein Mover
Authors: Pofantis Ermis , Neher Erwin , Dresbach Thomas
Published: January 2021

Significance

At active zones, ubiquitous proteins tether neurotransmitter-laden vesicles to specialized release sites, make them fusion-competent, and regulate their exocytotic fusion. Can specialized, synapse-specific proteins modulate this machinery? If so, which steps do they regulate? Here, we study mice lacking the presynaptic protein Mover. Mover is absent in some invertebrates and restricted to certain synapses in the rodent brain. Using electrophysiology and mathematical analysis of transmitter release kinetics at the calyx of Held, we find that Mover regulates a subset of fusion-competent synaptic vesicles: Mover selectively affects the vesicles most poised to be released during the initial stages of activity. Thus, by analogy, if ubiquitous proteins are light switches, Mover is a dimmer in transmitter release.
Natural cystatin C fragments inhibit GPR15-mediated HIV and SIV infection without interfering with GPR15L signaling
Authors: Hayn Manuel , Blötz Andrea , Rodríguez Armando , Vidal Solange , Preising Nico , Ständker Ludger , Wiese Sebastian , Stürzel Christina M. , Harms Mirja , Gross Rüdiger , Jung Christoph , Kiene Miriam , Jacob Timo , Pöhlmann Stefan , Forssmann Wolf-Georg , Münch Jan , Sparrer Konstantin M. J. , Seuwen Klaus , Hahn Beatrice H. , Kirchhoff Frank
Published: January 2021

Significance

G protein-coupled receptors (GPCRs) are involved in many physiological processes and important drug targets. However, most therapeutic agents targeting GPCRs, such as the coreceptors of HIV-1 CCR5 and CXCR4, also interfere with their signaling function. Here, we used primate lentiviruses as tools to discover novel endogenous ligands of GPR15, a coreceptor for HIV-2 and SIV proposed to play a role in mucosal immunity. We found that C-terminal fragments of cystatin C generated by immune-activated proteases inhibit GPR15-mediated HIV and SIV infection without interfering with GPR15L chemokine signaling. Thus, we identified an endogenous bioactive peptide that specifically prevents the detrimental activity of a GPCR (i.e. virus infection) without compromising its physiological signaling function.
Free NPs as units in Finnish
Authors: Helasvuo Marja-Liisa
Published: January 2021

This article focuses on free NPs, i.e. noun phrases that are grammatically not part of any clause but form units
of their own. Using the methodology of discourse-functional and interactional linguistics, I analyze the morphosyntactic, prosodic
and interactional features of free NPs in conversational Finnish. With its rich morphological marking, Finnish provides an
interesting perspective on free NPs: Morphosyntactic features, together with semantics, are crucial in determining the status of
an NP as a clausal constituent or a free NP. The prosodic analysis shows that the majority of free NPs show clear prosodic
boundaries, signalled for example by speaker change, coherent intonation contour, pause or pitch reset. Free NPs serve various
interactional functions, such as making assessments or disambiguating referents. These are functions which operate on something
already established in the discourse. Free NPs, however, can also initiate something new for example by making requests or
introducing new topics.
Constructional creativity in a Romance language
Authors: Busso Lucia
Published: January 2021

The present contribution summarizes findings on the understudied area of Italian valency coercion – i. e. the interaction of verbs and argument structure constructions in novel and creative ways – from four different studies. It highlights their innovative character, theoretical significance, and crosslinguistic implications for Construction Grammar. The paper suggests that valency coercion resolution involve different phenomena, such as distributional properties of constructions and compatibility between verb and construction. Sociolinguistic factors such as age and diatopic variables are also suggested to be relevant.
Argument structure satisfaction via unselected adjuncts
Authors: Fujii Seiko , Lee-Goldman Russell
Published: January 2021

This paper presents a frame-based constructional approach to argument structure satisfaction via unselected adjuncts, by
focusing on one such case in Japanese. It points out an intriguing constructional phenomenon whereby causal adjunct clauses marked with
node ‘because’, as used with main-clause predicates that evoke communication frames (such as Telling and
Warning), serve to satisfy main-clause argument structure. The node clause precedes the main-clause speech act of
telling/warning, and can be interpreted as a speech-act causal (Sweetser 1990). The
node clause at the same time conveys the content of informing or warning, i.e., the core Frame Element message,
which is absent as a main-clause complement. This analysis of argument structure satisfaction via unselected adjuncts provides evidence for
a Frame Semantic approach to argument structure that incorporates Construction Grammar.
Va a ser que no
Authors: Garachana Mar , Sansiñena María Sol
Published: January 2021

This study seeks to gain a better insight into the origin and expansion of the construction <va a ser que
sí/no
> (lit. goes to be that yes/no) in Peninsular Spanish. We argue that this construction derives from the use of the
periphrastic future construction  in a pseudo-cleft sentence whose subject is a deictic
element or an element that conveys the speaker’s attitudinal assessment of the propositional content expressed in the attribute, a
complement que-clause. The etymological structure evolves through a process that formally implies the suppression of the
explicit subject and the fusion of the components va a ser que leading to the conventionalization of refutative and
assertive values. To demonstrate this directionality, we examine recent stages of change and develop syntactic and semantic-pragmatic
arguments grounded in a data-based approach.