bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetochiroptical nanocavities in hyperbolic metamaterials enable sensing down to the few-molecule level
Authors: Carvalho William O. F. , Oliveira Osvaldo N. , Mejía-Salazar J. R.
Published: February 2024

In this work, we combine the concepts of magnetic circular dichroism, nanocavities, and magneto-optical hyperbolic metamaterials (MO-HMMs) to demonstrate an approach for sensing down to a few molecules. Our proposal comprises a multilayer MO-HMM with a square, two-dimensional arrangement of nanocavities. The magnetization of the system is considered in polar configuration, i.e., in the plane of polarization and perpendicular to the plane of the multilayer structure. This allows for magneto-optical chirality to be induced through the polar magneto-optical Kerr effect, which is exhibited by reflected light from the nanostructure. Numerical analyses under the magnetization saturation condition indicate that magnetic circular dichroism peaks can be used instead of reflectance dips to monitor refractive index changes in the analyte region. Significantly, we obtained a relatively high sensitivity value of S = 40 nm/RIU for the case where refractive index changes are limited to the volume inside nanocavities, i.e., in the limit of a few molecules (or ultralow concentrations), while a very large sensitivity of S = 532 nm/RIU is calculated for the analyte region distributed along the entire superstrate layer.
Preliminary study of dual annular multiple-beam cathode for V-band coaxial transit-time oscillator
Authors: Zeng Fanbo , Zhang Jiande , He Juntao , Ling Junpu
Published: February 2024

Since the research toward high-power millimeter-wave generator becomes a tendency in high-power microwave, overmoded structure with the high-order mode has been a considerable interest because of its potential to increase power handling capacity (PHC). To expand the PHC of V-band transit-time oscillator and excite higher mode TM03, a dual annular multiple-beam cathode has been proposed. In the geometric structure of the dual annular multiple-beam diode, cathode rods around two concentric circles are uniformly placed on cathode base, and each circle has several graphite rods. Because of space charge shielding effect and fluctuation of electron beam, explosive emission current of inner and outer cathode circles is difficult to be balanced, and the electron beam transmission rate is not very high. To solve those two problems, the relative length (ΔL) and the relative radius (Δr) between the inner and outer cathode circles are optimized to obtain balanced currents of inner and outer beams and a good transmission rate. In this paper, the preliminary study of a dual annular multiple-beam cathode is carried out by optimizing the cathode structure. When ΔL and Δr are equal to 2.5 and 4 mm, respectively, the dual annular multiple-beams cathode can provide 2.71 kA uniform intense relativistic electron beams under 421 kV, and the magnetic field is 1.2T. As a simulation result, explosively emitted and the 95.2% of total beam current transmission rate can be reached.
The stabilizing effect of collision on sheet instability in laser radiation pressure-based ion acceleration: A theoretical and simulation analysis
Authors: Sharbati Pouyan , Hasanbeigi Ali , Hajisharifi Kamal , Mehdian Hassan
Published: February 2024

In the past decade, transverse instabilities in the ion acceleration process using the laser radiation pressure method have been a prominent topic of discussion. These instabilities caused by the coupling between quasi-static ions with oscillating electrons through the ponderomotive force lead to the creation of density ripples in the target, ultimately resulting in the breaking of the target. This article investigates the collisional effects on the instability characteristic through theoretical and two-dimensional PIC simulation analysis. In agreement with our simulation studies, theoretical results show that the collision term enhanced the ion acceleration by decreasing the ion density accumulation and temporal growth rate of instability.
Non-radiative configurations of a few quantum emitters ensembles: Evolutionary optimization approach
Authors: Volkov Ilya , Mitsai Stanislav , Zhogolev Stepan , Kornovan Danil , Sheremet Alexandra , Savelev Roman , Petrov Mihail
Published: February 2024

Suppressing the spontaneous emission in quantum emitters ensembles (atoms) is one of the topical problems in quantum optics and quantum technology. While many approaches are based on utilizing the subradiance effect in ordered quantum emitters arrays, the ensemble configurations providing the minimal spontaneous emission rate are yet unknown. In this work, we employ the differential evolution algorithm to identify the optimal configurations of a few atomic ensembles that support quantum states with maximal radiative lifetime. We demonstrate that atoms tend to assemble mostly in quasi-regular structures with specific geometry, which strongly depends on the minimally allowed interatomic distance rmin. While the discovered specific non-radiative realizations of small ensembles cannot be immediately predicted, there is particular correspondence to the non-radiative states in the atomic lattices. In particular, we have found that states inheriting their properties either from the bound states in the continuum or band edge states of infinite lattices dominate across a wide range of rmin values. Additionally, we show that for small interatomic distances, the linear arrays with modulated spacing have the smallest radiative losses exponentially decreasing as the size of the ensemble increases.
Translational and reorientational dynamics in carboxylic acid-based deep eutectic solvents
Authors: Schulz A. , Moch K. , Hinz Y. , Lunkenheimer P. , Böhmer R.
Published: February 2024

The glass formation and the dipolar reorientational motions in deep eutectic solvents (DESs) are frequently overlooked, despite their crucial role in defining the room-temperature physiochemical properties. To understand the effects of these dynamics on the ionic conductivity and their relation to the mechanical properties of the DES, we conducted broadband dielectric and rheological spectroscopy over a wide temperature range on three well-established carboxylic acid-based natural DESs. These are the eutectic mixtures of choline chloride with oxalic acid (oxaline), malonic acid (maline), and phenylacetic acid (phenylaceline). In all three DESs, we observe signs of a glass transition in the temperature dependence of their dipolar reorientational and structural dynamics, as well as varying degrees of motional decoupling between the different observed dynamics. Maline and oxaline display a breaking of the Walden rule near the glass-transition temperature, while the relation between the dc conductivity and dipolar relaxation time in both maline and phenylaceline is best described by a power law. The glass-forming properties of the investigated systems not only govern the orientational dipolar motions and rheological properties, which are of interest from a fundamental point of view, but they also affect the dc conductivity, even at room temperature, which is of high technical relevance.
Modeling the effect of shape deformation induced by gravity on the evaporation of pendant and sessile drops
Authors: Tonini S. , Cossali G. E.
Published: February 2024

Pendant and sessile drops form a spherical cap only in the absence of gravity. The effect of gravity on drop shape is often neglected on the basis of the assumption that the drop size is smaller than the capillary length [Lc=(σ/gρ)1/2], although the deformation may not be fully negligible even in those cases. This paper focuses on evaluation of the effect that deformation due to gravity has on the evaporation characteristics of pendant and sessile drops. The drop shape is described by the Bashforth–Adams equation, a non-linear second order ordinary differential equation, which is solved numerically using a Runge–Kutta method with variable time steps. Under quasi-steady approximation, the species and energy conservation equations in the gas phase have analytical solutions, even for temperature-dependent gas thermophysical properties, once the solution of a basic Laplace problem is known. The Laplace equation is solved in axial symmetric geometry by using COMSOL Multiphysics®, for a wide range of drop sizes and contact angles, yielding vapor distribution, vapor fluxes, and evaporation rates. Comparison with the results from drops of same size in microgravity (i.e., having a spherical cap shape) shows that the effect is also perceptible for drops with a size smaller than the capillary length and that it can become quite important for those with larger sizes. Complementary results are found for sessile and pendant drops with respect to wall wettability, suggesting that the phenomenon can be analyzed using a unitary approach.
Supersaturation dependent nucleation of methane + propane mixed-gas hydrate
Authors: Uchida Tsutomu , Sugibuchi Ren , Hayama Masato , Yamazaki Kenji
Published: February 2024

Before hydrates can be widely used in industry, we should better understand the problematic issues of hydrate nucleation, particularly its stochastic nature. Here, we report on measurements of the nucleation probability of mixed-gas hydrates in which the guest molecules are a mixture of methane and propane. For the pure cases, at a supersaturation near 1.0, we had previously measured an induction time for the methane hydrate of about 1 h, whereas for the propane hydrate, it was over one day. Using the same experimental setup, we examine here the nucleation probability for a mixture of 90% methane and 10% propane as the guest gas for a range of supersaturations. For the experiments, the temperature was 274 ± 0.5 K and the stirring rate was about 300 rpm. The experiments were repeated at least ten times under the same condition, exchanging the sample water every time. We define the nucleation probability at a given time as the fraction of trials that nucleated by that time and then determine the nucleation probability distribution. The resulting nucleation frequency is found to have a power-law relation to supersaturation. Then, we examine how the nucleation frequency is affected by the existence of ultrafine bubbles in the initial water. We find that the ultrafine bubbles increase the nucleation frequency but much less than that of typical changes in supersaturation.
Shubnikov–de Haas oscillations of biaxial-strain-tuned superconductors in pulsed magnetic field up to 60 T
Authors: Yip King Yau , Wang Lingfei , Poon Tsz Fung , Yu Kai Ham , Lam Siu Tung , Lai Kwing To , Singleton John , Balakirev Fedor F. , Goh Swee K.
Published: February 2024

Two-dimensional (2D) materials have gained increasing prominence not only in fundamental research but also in daily applications. However, to fully harness their potential, it is crucial to optimize their properties with an external parameter and track the electronic structure simultaneously. Magnetotransport over a wide magnetic field range is a powerful method to probe the electronic structure and, for metallic 2D materials, quantum oscillations superimposed on the transport signals encode Fermi surface parameters. In this manuscript, we utilize biaxial strain as an external tuning parameter and investigate the effects of strain on the electronic properties of two quasi-2D superconductors, MoTe2 and RbV3Sb5, by measuring their magnetoresistance in pulsed magnetic fields up to 60 T. With a careful selection of insulating substrates, we demonstrate the possibility of both the compressive and tensile biaxial strains imposed on MoTe2 and RbV3Sb5, respectively. For both systems, the applied strain has led to superconducting critical temperature enhancement compared to their free-standing counterparts, proving the effectiveness of this biaxial strain method at cryogenic temperatures. Clear quantum oscillations in the magnetoresistance—the Shubnikov–de Haas (SdH) effect—are obtained in both samples. In strained MoTe2, the magnetoresistance exhibits a nearly quadratic dependence on the magnetic field and remains non-saturating even at the highest field, whereas in strained RbV3Sb5, two SdH frequencies showed a substantial enhancement in effective mass values, hinting at a possible enhancement of charge fluctuations. Our results demonstrate that combining biaxial strain and pulsed magnetic field paves the way for studying 2D materials under unprecedented conditions.
An improved axisymmetric interfacial lattice Boltzmann flux solver for large-density-ratio multiphase flows
Authors: Yang Liuming , Yang Xinmeng , Yang Yunfei , Hou Guoxiang , Wang Yan
Published: February 2024

In this paper, an improved axisymmetric interfacial lattice Boltzmann flux solver abandoning the previous predictor-corrector scheme is proposed. Unlike the previous model starting from the two-dimensional standard lattice Boltzmann method (LBM), the present method is developed using the axisymmetric LBM, which directly incorporates the axisymmetric effects into the distribution functions. As a result, the proposed solver does not need the corrector step involving complicated space derivatives. It makes this method simpler and more computationally efficient. In the present solver, the resultant governing equation is globally resolved by the finite volume method, while the fluxes are reconstructed by local application of the axisymmetric LBM. Therefore, the inconsistency between the local reconstruction and the global governing equation can be eliminated because the global equation can be strictly derived from the axisymmetric LBM, which holds stronger physical basis than the previous method. Numerical experiments about the interface capturing and the multiphase flows are conducted to test the proposed model. Results show that the present method is superior to the fractional step solver in terms of the accuracy, stability, and computational efficiency. In addition, this solver has the capacity of simulating large-density-ratio and complex interfacial change.
Strain-controlled Néel temperature and exchange bias enhancements in IrMn/CoFeB bilayers
Authors: Zhang Chenyu , Zhang Zhengming , Wang Dunhui , Hu Yong
Published: February 2024

We propose a numerical method, where first-principles calculations are combined with modified Monte Carlo simulations, and study the Néel temperature of antiferromagnetic IrMn and exchange bias effect in antiferromagnet/ferromagnet IrMn/CoFeB bilayers manipulated by the applications of tensile and compressive strains. The results show that both tensile and compressive strains linearly change the magnetic moment of Mn and the magnetocrystalline anisotropy of IrMn, and meanwhile, the uniaxially easy-axis directions under tensile and compressive strains are perpendicular. The strain-triggered increase in antiferromagnetic exchange coupling between Mn–Mn pairs is revealed and induces an up to 1.5 times enhancement of the Néel temperature of IrMn. Furthermore, the spontaneous and conventional exchange bias effects can be both observed under large tensile strains, also sensitive to the cooling field, and strongly enhanced roughly by 800% under 8 T in the application of 1.5% strain, which can be interpreted by the strain-induced high magnetocrystalline anisotropies. Thus, the tensile strains are better for controlling and optimizing the Néel temperature of IrMn and further exchange bias properties in IrMn-based heterostructures. This work establishes the correlations between microscopically and macroscopically magnetic responses to strain, indicating that strain can be an intriguing means of extrinsic manipulation of exchange bias, which is of importance for spintronic device applications.
Application of nanogenerators in acoustics based on artificial intelligence and machine learning
Authors: Yu Xiaofei , Ai Tengtian , Wang Kai
Published: February 2024

As artificial intelligence (AI) advances, it is critical to give conventional electronics the capacity to “think,” “analyze,” and “advise.” The need for intelligent, self-powered devices has increased due to recent significant developments in the computer field, namely, in the fields of AI and machine learning (ML). The use of nanogenerators in the area of acoustics is examined in this Review, with an emphasis on how they might be integrated with ML and AI. Innovative energy-harvesting devices called nanogenerators are able to produce electrical power from outside sources, such as vibrations in the air or mechanical movements. The study examines a number of acoustic applications for nanogenerators, such as energy harvesting, sound detection, noise monitoring, and acoustic sensing. Furthermore, the research highlights how AI and ML techniques enhance the performance of nanogenerators and enable more efficient acoustic applications through data analysis and model training. At the end of this Review, the future development prospects of nanogenerators based on AI and ML were discussed.
The spindle protein CKAP2 regulates microtubule dynamics and ensures faithful chromosome segregation
Authors: Paim Lia Mara Gomes , Lopez-Jauregui Azriel Abraham , McAlear Thomas S. , Bechstedt Susanne
Published: February 2024

Regulation of microtubule dynamics by microtubule-associated proteins (MAPs) is essential for mitotic spindle assembly and chromosome segregation. Altered microtubule dynamics, particularly increased microtubule growth rates, were found to be a contributing factor for the development of chromosomal instability, which potentiates tumorigenesis. The MAP XMAP215/CKAP5 is the only known microtubule growth factor, and whether other MAPs regulate microtubule growth in cells is unclear. Our recent in vitro reconstitution experiments have demonstrated that Cytoskeleton-Associated Protein 2 (CKAP2) increases microtubule nucleation and growth rates, and here, we find that CKAP2 is also an essential microtubule growth factor in cells. By applying CRISPR-Cas9 knock-in and knock-out (KO) as well as microtubule plus-end tracking live cell imaging, we show that CKAP2 is a mitotic spindle protein that ensures faithful chromosome segregation by regulating microtubule growth. Live cell imaging of endogenously labeled CKAP2 showed that it localizes to the spindle during mitosis and rapidly shifts its localization to the chromatin upon mitotic exit before being degraded. Cells lacking CKAP2 display reduced microtubule growth rates and an increased proportion of chromosome segregation errors and aneuploidy that may be a result of an accumulation of kinetochore–microtubule misattachments. Microtubule growth rates and chromosome segregation fidelity can be rescued upon ectopic CKAP2 expression in KO cells, revealing a direct link between CKAP2 expression and microtubule dynamics. Our results unveil a role of CKAP2 in regulating microtubule growth in cells and provide a mechanistic explanation for the oncogenic potential of CKAP2 misregulation.
On the validity of descriptors in ACTFL Language Proficiency Guidelines
Authors: Li Qijie , Feng Hao , Cui Yiping
Published: February 2024

ACTFL Language Proficiency Guidelines (hereinafter called Guidelines) are a
multi-lingual framework mainly based on the language proficiency development of several European languages. Little consideration
is given to the peculiarity of Chinese. Efforts are made to assess the validity of the descriptors in Guidelines
in comparison with Chinese Proficiency Grading Standards for International Chinese Language Education
(hereinafter called Standards). A total of five parameters from Guidelines that are not
compatible with Standards have been selected and two questionnaires compiled by the authors are answered by local
American Chinese language teachers to evaluate the validity of these descriptors. The study shows that the descriptors in
Standards are more valid in differentiating language proficiency levels of Chinese. In accordance with this
study, some revisions and amendments should be made to Guidelines.
MiPhDUO: microwave imaging via physics-informed deep unrolled optimization
Authors: Zumbo Sabrina , Mandija Stefano , Isernia Tommaso , Bevacqua Martina T
Published: February 2024

Microwave imaging (MWI) is a non-invasive technique that can identify unknown scatterer objects’ features while offering advantages such as low cost and portable devices with respect to other imaging methods. However, MWI faces challenges in solving the underlying inverse scattering problem, which involves recovering target properties from its scattered fields. Existing methods include linearized and non-linear optimization approaches, but they have limitations respectively in terms of range of validity and computational complexity (in view of the possible occurrence of ‘false solutions’). In recent years, learning-based approaches have emerged as they can allow real-time imaging but usually lack generalizability and a direct connection to the underlying physics. This paper proposes a physics-informed approach that combines convolutional neural networks with physics-based calculations. It is based on a few cascaded operations, making use of the gradient of the relevant cost function, and successively improving the estimation of the unknown target. The proposed approach is assessed using simulated as well as experimental Fresnel data. The results show that the integration of physics with deep learning can contribute to improve reconstruction accuracy, generalizability, and computational efficiency in MWI.
Dynamics of NO, N2O, and ONOOH in atmospheric-pressure air dielectric barrier discharge: decoupling energy density and gas temperature effects varying with discharge voltage
Authors: Zhou Xiong-Feng , Geng Wen-Qiang , Ma Xiang-Yu , Ran Cong-Fu , Liu Kun
Published: February 2024

The dose regulation of reactive nitrogen species is crucial for biomedical applications. In this study, we develop a global chemical kinetics model comprising 92 species and 1018 reactions to investigate the regulatory dynamics of three types of reactive nitrogen species, i.e. NO, N2O, and ONOOH, which vary with the discharge voltage in an air coaxial dielectric barrier discharge. Based on the experimental results, the model can describe the density variations of NO, N2O, and ONOOH. The simulation results indicate that the O,

NO

3
−

,

NO

2
−

, and O3 are essential intermediate species related to NO generation; N, NO2, O-, N2*, and O(1D) are essential intermediate species related to N2O generation; and

O

2
−

, NO, NO2, OH,

O

4
−

, and O3 are essential intermediate species related to ONOOH generation. The individual and comprehensive effects of the energy density and gas temperature on the densities of NO, N2O, and ONOOH and the corresponding intermediate species are quantified under increasing discharge voltages. The simulation results indicate that the energy density is the primary factor affecting the number density of NO, N2O, and ONOOH, whereas the gas temperature exerts a completely different effect on these three species. These insights are valuable for plasma applications in biomedicine, where the selective and controlled production of reactive nitrogen species is key for achieving the desired plasma performance.
Fast breakdown process and characteristics diagnosis of nanosecond pin–pin discharge
Authors: Li Yao , Li Si-Si , Feng Yi , Qie Shao-Ming , Yuan Hao , Yang De-Zheng
Published: February 2024

In this paper, the characteristics of a nanosecond spark discharge with a pin–pin electrode configuration have been systematically studied. Both a streak camera with high temporal resolution and an intensified charge-coupled device (ICCD) camera are employed together to investigate the breakdown and evolution process of the discharge. The formation of initial breakdown and mode transition from streamer to spark in the electrode gap are clearly observed on the time scale of several nanoseconds with a temporal resolution of 100 ps. In addition, the time-resolved spectra technology is also used to analyze the generation and quenching mechanisms of reactive species, the electron density, and the electron temperature. The results show that there is a 1.25 ns initial discharge breakdown and that a bright cathode spot exists before the transformation from streamer to spark channel. After a faster cathode filament and a slower anode filament propagate and merge at the electrode gap, the spark discharge phase begins. The generation processes of different reactive species depend on the discharge phase to a great extent. The N2* is first generated during the streamer phase while the O*, N*, and N+ are mainly generated under the spark phase, in which the electron temperature calculated by Boltzmann plots is 2.74 eV, and the electron density determined from the Stark broadening of O lines is on the order of 1016 cm−3.
Maximal circular polarization isolation and asymmetric polarization conversion by chiral meta-structure
Authors: Hussain Shahid , Maroof Zubaria , Ahmed Faizan , Ji Ruonan , Wang Shaowei
Published: February 2024

Chiral objects hold immense significance in modern optical technology, particularly due to their ability to manipulate circularly polarized waves. The chiroptical effects observed in naturally known chiral structures are typically very weak, however, the use of engineered meta-structures has proven to be highly effective in overcoming these shortcomings. Despite extensive research efforts, the construction of chiroptical phenomena approaching maximum performance has proven to be challenging, mostly due to the lack of optimal design choices and the existence of material losses. Here we present a metasurface constituting S-shaped building blocks capable of realizing virtually maximum chiroptical phenomena. The structure demonstrates nearly full polarization transmission, conversion to an opposite spin state, and reflection of the opposite spin state at a wavelength of 1549 nm. As a result, the maximum circular dichroism (CD) value reaches up to ≈1 (0.9993) for a given polarization state. Furthermore, reduced symmetry enables the one-way flow of a given polarization state resulting in about unity (0.998) asymmetric transmission (AT) value. Through rigorous numerical simulations, we elucidate the underlying principles driving these extraordinary optical properties. The CD and AT values are record-high demonstrated so far. The single-layer design offers an ultrathin profile, making it compatible with integrated photonics and providing opportunities for applications in compact, lightweight optical devices such as circular polarizers, half-wave plates, and self-polarizing reflectors.
Superconducting properties of bismuthate/manganite epitaxial multilayers
Authors: Komori Sachio , Taniyama Tomoyasu
Published: February 2024

We report epitaxial growth and superconducting properties of superconductor/ferromagnet (S/F) multilayers consisting of an s-wave superconducting bismuthate BaPb0.75Bi0.25O3 (BPBO) and a ferromagnetic insulating manganite La0.875Sr0.125MnO3 (LSMO). We demonstrate that the superconductivity of BPBO sandwiched by LSMO is preserved down to a thickness close to the superconducting coherence length. The superconducting transition temperature of BPBO is unaffected by the magnetization alignment of the LSMO layers, which is in sharp contrast to YBa2Cu3O7 showing a clear magnetic exchange interaction. While the stable s-wave superconductivity in the S/F oxide multilayer demonstrated in this work is promising for the development of quantum spin devices with strong spin–orbit coupling, the absence of the magnetic exchange field effect highlights the importance of interface engineering for the realization of a strongly exchange-coupled s-wave S/F oxide interface.
Revealing the effect of bridges in the multi-filamentary Bi-2212 wires
Authors: Zhang Zhen-Chuang , Yu Min , Yang Dong-Sheng , Zhou Meng-Liang , Zhou Hai-Shan , Qin Jing-Gang
Published: February 2024

As the excellent current carrying capacity in ultra-high magnetic fields, Bi-2212(Bi2Sr2CaCu2O8+x
) has attracted much attention. In view of the unique nature of Bi-2212, high-temperature heat treatment is highly needed for the formation of the continuous textured structure in the multi-filamentary Bi-2212 wire. In the meanwhile, bridges between filaments can also be produced in the heat treatment process, which brings structural changes in the wires. However, the mechanism of the effect of the bridges is yet to be understood. In this work, systematical research was carried out on the multi-filamentary Bi-2212 wire for the effect mechanism. Based on the results of the four-probe method and the magnetic moment results, inferiority in Ic
combined with a larger magnetic moment at high magnetic fields was detected in samples that have a large number of bridges. Further analysis indicates the inferiority in Ic
can be attributed to the reduced cross-sectional area of the filaments and the inferiority in the quality of texture on the basis of results of a series of structural characterizations.
Proposal of ensemble qubits with two-atom decay
Authors: Qin Wei , Miranowicz Adam , Nori Franco
Published: February 2024

We propose and analyze a novel approach to implement ensemble qubits. The required anharmonicity is provided by a simultaneous decay of two atoms (i.e. two-atom decay), which is achieved by fully quantum degenerate parametric amplification. For an atomic ensemble, the two-atom decay generates and stabilizes a 2D quantum manifold, which is spanned by the ground and single-excited superradiant states. Moreover, this nonlinear decay process can strongly suppress transitions to higher-excited superradiant states, and convert residual transitions into an effective decay from the single-excitation superradiant state to the ground state. Our method does not require Rydberg dipole blockade and, thus, strong atom-atom interactions, compared to previous work. This indicates that it can be applied to typical atomic or spin ensembles in simple experimental setups. Remarkably, our idea is compatible with the cavity protection mechanism, and therefore spin dephasing due to inhomogeneous broadening can be strongly suppressed. The presented ensemble qubit provides a new platform for quantum information processing, and also extends the range of applications of atomic or spin ensembles.
A machine learning approach to predict the efficiency of corrosion inhibition by natural product-based organic inhibitors
Authors: Akrom Muhamad , Rustad Supriadi , Dipojono Hermawan Kresno
Published: February 2024

This paper presents a quantitative structure–property relationship (QSPR)-based machine learning (ML) framework designed for predicting corrosion inhibition efficiency (CIE) values in natural organic inhibitor compounds. The modeling dataset comprises 50 natural organic compounds, with 11 quantum chemical properties (QCP) serving as input features, and the target variable being the corrosion inhibition efficiency (CIE) value. To enhance the predictive accuracy of the ML model, the kernel density estimation (KDE) function is employed to generate virtual samples during the training process, with the overarching goal of refining the precision of the ML model. Three distinct models, namely random forest (RF), gradient boosting (GB), and k-nearest neighbor (KNN), are tested in the study. The results demonstrate a noteworthy enhancement in the prediction performance of the models, attributable to the incorporation of virtual samples that effectively improve the correlation between input features and target values. Consequently, the accuracy of the predicted CIE values is significantly augmented, aligning more closely with the actual CIE values. Performance improvements were evident across all models after the incorporation of virtual samples. The GB, RF, and KNN models exhibited increments in R2 values from 0.557 to 0.996, 0.522 to 0.999, and 0.415 to 0.994, respectively, concomitant with the introduction of 500 virtual samples. Additionally, each model demonstrated a notable reduction in RMSE values, transitioning from 1.41 to 0.19, 1.27 to 0.10, and 1.22 to 0.16, respectively. While the GB model initially outperformed others before the addition of virtual samples, the performance of the model exhibited fluctuation as the number of virtual samples varied. This behavior suggests that the KDE function provides a certain level of resilience against model variations. The proposed approach contributes to the effective design and exploration of corrosion inhibitor candidates, offering a reliable and accurate predictive tool that bridges the gap between theoretical studies and experimental synthesis.
A new superior electronic properties Si allotrope for power electronic device applications
Authors: Wang Yulong , Duan Baoxing , Yang Yintang
Published: February 2024

A new I−4 space group silicon allotrope is proposed in this paper. The electronics properties, mechanical properties and Ag(100)/I4Si(100) interface properties are studied using first principle calculations method. The results of the phonon show that I−4 Si is dynamically stable. Elastic constants reveal I−4 Si is dynamical stable. Electronics properties calculations reveal that the CBM and VBM of I−4 Si are at X and M point, which indicates that I−4 Si is an indirect band gap semiconductor with a high band gap of 1.95 eV. To satisfy the demands for fabricating electronic devices, the N-type doping, P-type doping and Ohmic contact are studied, too. The fermi energy level of N-type and P-type I−4 Si move into conduction band and valence band, respectively. The Schottky barrier of Ag/I-4 interface is 0.65 eV. Meanwhile, the current-voltage curve becomes highly symmetric, suggesting an Ohmic behavior of the Ag(100)/I4Si(100) interface. Critical breakdown field calculations results show that the critical breakdown field of I−4 Si is 9.05 × 105 V cm−1, which is 3.02 times that of the diamond Si. Because band gap and critical breakdown field of I-4 Si are much greater than that of diamond Si, I-4 Si is potential electronic semiconductor material. Thus, I−4 Si can be applied in the field of modern power electronic device applications due to its superior electronic properties.
High-pressure study on calcium azide (Ca(N3)2): Bending of azide ions stabilizes the structure
Authors: Wu 武 Xiaoxin 晓鑫 , Wang 王 Yingjian 颖健 , Li 李 Siqi 思琪 , Lv 吕 Juncheng 俊呈 , Wang 王 Jingshu 婧姝 , Yang 杨 Lihua 丽华 , Zhang 张 Qi 旗 , Liu 刘 Yanqing 艳清 , Zhang 张 Junkai 俊凯 , Jia 贾 Hongsheng 洪声
Published: February 2024

The high-pressure structure and elastic properties of calcium azide (Ca(N3)2) were investigated using in-situ high-pressure x-ray diffraction and Raman scattering up to 54 GPa and 19 GPa, respectively. The compressibility of Ca(N3)2 changed as the pressure increased, and no phase transition occurred within the pressure from ambient pressure up to 54 GPa. The measured zero-pressure bulk modulus of Ca(N3)2 is higher than that of other alkali metal azides, due to differences in the ionic character of their metal-azide bonds. Using CASTEP, all vibration modes of Ca(N3)2 were accurately identified in the vibrational spectrum at ambient pressure. In the high-pressure vibration study, several external modes (ext.) and internal bending modes (ν
2) of azide anions (

N
3
−

) softened up to ∼7 GPa and then hardened beyond that pressure. This evidence is consistent with the variation observed in the F
E–f
E data analyzed from the XRD result, where the slope of the curve changes at 7.1 GPa. The main behaviors under pressure are the alternating compression, rotation, and bending of

N
3
−

ions. The bending behavior makes the structure of Ca(N3)2 more stable under pressure.
Gravitational wave footprints from Higgs-portal scalegenesis with multiple dark chiral scalars*
Authors: Zhang 张 He-Xu 贺旭 , Matsuzaki Shinya , Ishida Hiroyuki
Published: February 2024

We discuss the gravitational wave (GW) spectra predicted from the electroweak scalegenesis of the Higgs portal type with a large number of dark chiral flavors, which many flavor QCD would underlie and give the dynamical explanation of the negative Higgs portal coupling required to trigger the electroweak symmetry breaking. We employ the linear-sigma model as the low-energy description of dark many flavor QCD and show that the model undergoes ultra-supercooling due to the produced strong first-order thermal phase transition along the (approximately realized) flat direction based on the Gildener-Weinberg mechanism. Passing through evaluation of the bubble nucleation/percolation, we address the reheating and relaxation processes, which are generically non-thermal and nonadiabatic. Parametrizing the reheating epoch in terms of the e-folding number, we propose proper formulae for the redshift effects on the GW frequencies and signal spectra. It then turns out that the ultra-supercooling predicted from the Higgs-portal scalegenesis generically yields none of GW signals with the frequencies as low as nano Hz, unless the released latent heat is transported into another sector other than reheating the universe. Instead, models of this class prefer to give the higher frequency signals and still keeps the future prospected detection sensitivity, like at LISA, BBO, and DECIGO, etc. We also find that with large flavors in the dark sector, the GW signals are made further smaller and the peak frequencies higher. Characteristic phenomenological consequences related to the multiple chiral scalars include the prediction of dark pions with the mass much less than TeV scale, which is also briefly addressed.
Cross sections for 14 MeV neutron interaction with lutetium isotopes and their theoretical excitation functions*
Authors: Song 宋 Yueli 月丽 , Zhou 周 Fengqun 丰群 , Li 李 Yong 勇 , Zhang 张 Xiaopeng 晓朋 , Ji 姬 Pengfei 鹏飞 , Sun 孙 Xiaojun 小军
Published: February 2024

The cross-sections for the 175Lu(n,p)175Yb, 175Lu(n,α)172Tm, 176Lu(n,α)173Tm, 175Lu(n,2n)174mLu, and 175Lu(n,2n)174gLu reactions at 13.57, 14.03 14.62, and 14.86 MeV neutron energies were measured using an activation technique. The theoretical excitation functions of these reactions were calculated using the Talys-1.95 code. The reaction cross-section data experimentally obtained were analyzed and compared with experimental data reported in the literature, data from five major evaluated nuclear data libraries of IAEA, and theoretical values based on Talys-1.95. The data obtained at some neutron energies agree with some of the data reported in the literature and theoretical values based on Talys-1.95. The consistency of the theoretical curves of excitation functions based on Talys-1.95 with the data obtained in this study and those reported in the literature is higher than that of the evaluation curves of excitation functions for the 175Lu(n,p)175Yb, 175Lu(n,α)172 Tm, and 176Lu(n,α)173Tm reactions. This study is helpful because it provides new evaluated reaction cross-section data on lutetium (which is a fusion reactor material), improves the quality of neutron-induced reaction cross section data libraries, and advances the research on related applications.
An experimental study of pedestrian bidirectional flow through bottlenecks
Authors: Jia Xinmiao , Jiang Nan , Zhang Ping , Li Maoyu , Yu Hanchen , Ju Xiaoyu , Yang Lizhong
Published: February 2024

Pedestrian flow passing through bottlenecks is complex, particularly for opposite movement in a room with a single doorway. These bidirectional flows would always cause congestion and further reduce traffic efficiency so the ‘Disembarking precedes embarking’ rule is widely used in the actual management of public spaces. However, the impact of the imbalance of the bidirectional movement of pedestrian numbers on the pedestrian capacity and throughput at the bottleneck still needs further exploration. Therefore, this study investigates the effects of the ratio r of pedestrians leaving the room to the total number of participants and the bottleneck widths (1.2, 1.6 and 2.0 m) on the movement behavior of pedestrians in bidirectional flow and the efficiency of passing through by conducting controlled experiments where pedestrian trajectories, speed, density, flow and time headway are analyzed. Results indicate that the bottleneck width and the pedestrian flow rate are linearly related, whereas the r and flow have a nonlinear relationship. Specifically, r = 10% is the optimal value for improving the pedestrian traffic efficiency at the bottleneck, which is even better than the unidirectional scenario. The most significant density in the measuring area is at r = 30%, corresponding to the greatest probability of clogging. The pedestrian density within the room influences the flow rate at the bottleneck, thereby indicating that wider doors are not always better from a design perspective. The findings presented in this paper can provide actual data to validate bidirectional pedestrian flow simulation models and theoretical support for pedestrian facility and crowd management optimization.
Overlap structure and free energy fluctuations in short-range spin glasses
Authors: Newman C M , Stein D L
Published: February 2024

We investigate scenarios in which the low-temperature phase of short-range spin glasses comprises thermodynamic states which are nontrivial mixtures of multiple incongruent pure state pairs. We construct a new kind of metastate supported on Gibbs states whose edge overlap values with a reference state fall within a specified range. Using this metastate we show that, in any dimension, the variance of free energy difference fluctuations between pure states within a single mixed Gibbs state with multiple edge overlap values diverges linearly with the volume. We discuss some implications of these results.
Vegetation types and habitats with participation of plant species – local endemics to the marble part of Northern Pirin Mts., Bulgaria
Authors: Nacheva Veradina , Tzonev Rossen , Pachedjieva Kalina , Kolchagov Rumen , Gussev Chavdar , Pavlova Dolja
Published: February 2024

This study was carried out in the carbonate (marble) part of North Pirin Mts. Its upper parts are declared protected area of National Park category according to the Bulgarian Protected Areas Act. It is also a NATURA 2000 protected zone under the Habitats Directive, and a natural UNESCO World Heritage Site. The main reason for the conservation of this territory is the exceptional concentration of rare, relict and endemic plant species, its specific flora, vegetation and fauna. Subject of the study are the plant communities and habitats, with participation of 8 local endemic plant taxa, such as Cyanus achtarovii, Oxytropis kozhuharovii, O. urumovii, Odontarrhena orbelica, Alyssum pirinicum, Veronica kellereri, Brassica nivalis subsp. jordanoffii and Arabis ferdinandi-coburgii. The plant communities were studied according to the classical Braun-Blanquet’s approach by sampling the phytocoenoses, where the local endemics participate. The major syntaxa to which these communities belong, were determined. The plant communities with the participation of local endemics were also referred to lower units according to EUNIS habitats classification. The study found that most of the studied endemic species occur in various vegetation types and exhibit relatively wide ecological flexibility, despite inhabiting restricted area. The main reason for this is the comparative uniformity of the high mountain marble relief. This study also highlights the high conservation value of the vegetation cover and habitat diversity of the carbonate alpine and subalpine vegetation belts of Northern Pirin Mts., as a habitat for numerous endemic and relict plant species.
An update to the genus Bolboschoenus in Bulgaria - species diversity, distribution and phytosociological affinities
Authors: Kunev G
Published: February 2024

The current study presents new data on the distribution of the representatives of the genus Bolboschoenus in Bulgaria and gives a brief description of their communities. It is based on revision of herbarium materials, field observations and phytosociological samples. Morphological characteristics and ecological traits of the studied taxa are commented. A synopsis of all collected chorological information is attached.
Comparison of the zooplankton-based RCC to Carlson’s trophic state indices and water quality parameters
Authors: Stanachkova Marieta , Dashinov Dimitriy , Traykov Ivan
Published: February 2024

Zooplankton is not included as a biological quality element, even though it is a key component of pelagic food webs. The data on zooplankton community structure can be used to evaluate the trophic state of lakes through an RCC Index, based on quantitative proportions between the main zooplankton groups. As previous investigations have related the index only to the Secchi disc transparency, the aim of this study was to compare the Index to a set of water quality parameters and trophic state indices. Two sandpit lakes with contrasting characteristics were selected as model lakes for the study. A total of 57 samples were collected simultaneously with the physicochemical water quality parameters between 2016 and 2020. Carlson’s trophic state indices were used to assess the trophic state of the lakes. Pearson correlation coefficient and Principal Component Analysis were used to assess the observed correlations between the measured parameters and to distinguish what factors regulate zooplankton community structure. Overall, 86 zooplankton taxa were identified. RCC Index ranged from 2 in the small sandpit lake to 87 in the big sandpit lake. A highly significant negative correlation was found between the RCC Index and the values of TP and COD. The results complement the arguments for the inclusion of zooplankton as a BQE for the assessment of the status of lakes.
Water Safety Plan: A case study from Sofia, Bulgaria
Authors: Aleksova M , Schneider I
Published: February 2024

According to Directive 2184/2020 on the quality of water intended for human consumption and World Health Organization (WHO) best practice, the Water Safety Plan (WSP) includes a review of the whole water supply chain – from protection of the water source, through water abstraction, transportation, treatment, storage and distribution to the end user. Risk management is based on the introduction of corrective, control and preventive measures, as well as subsequent validation of the measures taken and monitoring of their implementation according to the Deming cycle. The purpose of the current study is to review individual components of the WSP implementation and the effectiveness of WSP developed and implemented by Sofiyska voda JSC (SV) - the water supplier of Sofia, the capital of Bulgaria. The article presents the overall approach followed by the water supply operator, including the system review, risk identification and assessment, mitigation barriers, process control through critical control points (CCPs), review and verification of all risk management measures taken.