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We investigate the effect of Rashba spin-orbit coupling (RSOC) on photoconductivities of rectified currents in monolayer graphene with exchange field and sublattice potential. The system shows that the photoconductivities of resonant shift and injection current contributions are nonzero, while the photoconductivities of non resonant shift current contribution are zero. We find that the RSOC induces a warping term, which leads to the nonzero rectified currents. Moreover, the photoconductivities of resonant injection (shift) current contribution are (not) related to the relaxation rate. The similar behavior can be found in other Dirac materials, and our findings provide a way to tune the non-linear transport properties of Dirac materials.

A method to improve the spatial resolution of the radiant optical fiber temperature sensor is proposed in this paper. The front lens of the sensor is designed to limit the diameter of the thermometry target. In order to avoid limiting the influence of the thermometry target diameter on the sensor radiation-light coupling ability, a mathematical model of the radiation-light coupling of the sensor is established, and the relationship between the radiation-light coupling ability of the sensor and the diameter of the thermometry target is analyzed. Furthermore, an aspheric lens is applied to reduce the influence of aberration on the diameter of the thermometry target. The experimental results show that the deviation between the actual temperature measuring target diameter and the theoretical design value is less than 0.2 mm. The radiation received by the sensor outside the temperature measuring target is less than 10% of its total received radiation. Moreover, when there is radiated light interference outside the temperature measurement target, the temperature measurement error of the sensor is only 0.21%–2.61%, indicating that the proposed method has practical significance in improving the spatial resolution of the temperature measurement.

The SARS-CoV-2 Omicron variant has become the dominant variant in the world. Uncovering the structural basis of altered immune response and enhanced transmission of Omicron is particularly important. Here, taking twenty-five antibodies from four groups as examples, we comprehensively reveal the underlying mechanism of how mutations in Omicron induces the weak neutralization by using molecular simulations. Overall, the binding strength of 68% antibodies is weakened in Omicron, much larger than that in Delta (40%). Specifically, the percentage of the weakened antibodies vary largely in different groups. Moreover, the mutation-induced repulsion is mainly responsive for the weak neutralization in AB/CD groups but does not take effect in EF group. Significantly, we demonstrate that the disappearance of hydrophobic interaction and salt bridges due to residue deletions contributes to the decreased binding energy in NTD group. This work provides unprecedented atomistic details for the distinct neutralization of WT/Delta/Omicron, which informs prospective efforts to design antibodies/vaccines against Omicron.

The exceptional points (EPs) in a system are the eigenvalue degeneracy that has been demonstrated in a wide range of optical arrangements. In this paper, EP is analyzed schematically in an optically pumped magnetometer, which is governed by the Bloch equation with a 3 × 3 matrix. We numerically illustrate EP enhanced sensing for magnetic field and EP encircling induced 2π phase shift by employing the sensing field along with transverse modulation field. These findings may contribute to the realization of EP magnetometers and atomic gyroscopes for improved field and rotation sensitivity.

The molecular mechanics/Poisson–Boltzmann surface area (MM/PBSA) method has been widely used in predicting the binding affinity among ligands, proteins, and nucleic acids. However, the accuracy of the predicted binding energy by the standard MM/PBSA is not always good, especially in highly charged systems. In this work, we take the protein–nucleic acid complexes as an example, and showed that the use of screening electrostatic energy (instead of Coulomb electrostatic energy) in molecular mechanics can greatly improve the performance of MM/PBSA. In particular, the Pearson correlation coefficient of dataset II in the modified MM/PBSA (i.e., screening MM/PBSA) is about 0.52, much better than that (< 0.33) in the standard MM/PBSA. Further, we also evaluate the effect of solute dielectric constant and salt concentration on the performance of the screening MM/PBSA. The present study highlights the potential power of the screening MM/PBSA for predicting the binding energy in highly charged bio-systems.

Investigation of exceptional points mostly focuses on the second-order case and employs the gain-involved parity-time (PT) symmetric systems. Here, we propose an approach to implementing fourth-order exceptional points (FOEPs) using directly coupled optical resonators with rotation. On resonance, the system manifests FOEP through tuning the spinning velocity to targeted values. Eigenfrequency bifurcation and enhanced sensitivity for nanoparticle have been presented. Also, near FOEP, nonreciprocal light propagation exhibits great boost and dramatic change, which may be applied to high-efficiency isolators and circulators.

Triaxial uniform coils housed in magnetic shields are extensively used in atomic sensors. The coil constant can be affected by the magnetic shield that imposes a ferromagnetic boundary. This study numerically and experimentally analyzes the coil constant dependence on the Mn–Zn ferrite magnetic shield thickness, aspect ratio, air gaps between the magnetic annuli, and the distance from the coils. Results show that the radial coil constant (saddle-shaped coil) only depends upon the distance between the coil and the magnetic shield. The axial coil constant (Lee–Whiting coil) depends on the aspect ratio, distance between the coil and the magnetic shield, and air gap width between the magnetic annuli. The axial coil constant is linearly related to the air gap. When the thickness of the magnetic shield is greater than 2 mm, the radial and axial coil constants are independent of the shield thickness. The difference between the simulated and measured values is only 3.9%. The numerical calculation accuracy was verified by experimental measurements. This study can aid in the design and research of coils in the ferrite magnetic shield in atomic sensors.

The spread of the coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has become a global health crisis. The binding affinity of SARS-CoV-2 (in particular the receptor binding domain, RBD) to its receptor angiotensin converting enzyme 2 (ACE2) and the antibodies is of great importance in understanding the infectivity of COVID-19 and evaluating the candidate therapeutic for COVID-19. In this work, we propose a new method based on molecular mechanics/Poisson-Boltzmann surface area (MM/PBSA) to accurately calculate the free energy of SARS-CoV-2 RBD binding to ACE2 and antibodies. The calculated binding free energy of SARS-CoV-2 RBD to ACE2 is -13.3 kcal/mol, and that of SARS-CoV RBD to ACE2 is -11.4 kcal/mol, which agrees well with experimental result (-11.3 kcal/mol and -10.1 kcal/mol, respectively). Moreover, we take two recently reported antibodies as the example, and calculate the free energy of antibodies binding to SARS-CoV-2 RBD, which is also consistent with the experimental findings. Further, within the framework of the modified MM/PBSA, we determine the key residues and the main driving forces for the SARS-CoV-2 RBD/CB6 interaction by the computational alanine scanning method. The present study offers a computationally efficient and numerically reliable method to evaluate the free energy of SARS-CoV-2 binding to other proteins, which may stimulate the development of the therapeutics against the COVID-19 disease in real applications., 18 pages, 5 figures

In an optically pumped alkali vapor cell with a high density of atoms, the attenuation of the pump light generates a spatially non-uniform distribution of the electronic spin polarization of alkali atoms, which is detrimental to biomagnetism applications of magnetometers as well as the hyperpolarization of noble gas atoms. Therefore, in this study, we propose a new scheme to generate a nearly uniform, unsaturated spin polarization region based on counter-propagating pump beams and atomic diffusion. A finite element method-based simulation is used to demonstrate the three-dimensional distribution of the spin polarization in a spherical cell. The effects of cell temperature and pump light power on the homogeneity of the spin polarization are studied. The distribution of spin polarization near the center of the cell is experimentally measured and a 1 cm uniform spin polarization region is achieved in the center of the cell. The uniformity of spin polarization in the center region of the cell increased by 50% compared with single beam pumping. The advantage of our proposed scheme is that it can generate an unsaturated uniform region of spin polarization in the center of a cell using a single species of alkali atoms.

A spinning optical resonator is an excellent platform for realizing nonreciprocity. Here, we demonstrate the distinctive isolation features in spinning indirectly coupled resonators, where the nonreciprocal light propagation and probing mechanism via mechanical rotation have been achieved. Interplay with nanoparticles induces a tunable one- or two-way transmission through differential rotation, which can also be employed to realize the improved capability of particle detection. By pushing an individual resonator into a rotation-induced exceptional point (EP) condition, an EP associated isolation pattern is observed with avoided crossing. Our results may promote the development and understanding of nonreciprocity, rotation devices and anti-parity-time symmetry.

We propose a three-cavity coupled cavity optomechanical (COM) structure with tunable system parameters and theoretically investigate the probe-light transmission rate. Numerical calculation of the system’s spectra demonstrates distinctive compound-induced transparency (CIT) characteristics, including multiple transparency windows and sideband dips, which can be explained by a coupling between optomechanically-induced transparency (OMIT) and electromagnetically-induced transparency. The effects of optical loss (gain) in the cavity, number and topology of active cavity, tunneling ratio, and pump laser power on the CIT spectrum are evaluated and analyzed. Moreover, the optical group delay of CIT is highly controllable and fast–slow light inter-transition can be achieved. The proposed structure makes possible the advantageous tuning freedom and provides a potential platform for controlling light propagation and fast–slow light switching.

Mu-metal shields are widely used in atomic devices, but their magnetic noise related to loss is the key performance limit. The magnetic noise can be calculated by using complex permeability and the magnetic field intensity in the shield. In this study, Bertotti loss separation is used for the first time to accurately calculate the changes of complex permeability due to the hysteresis loss in different frequencies and magnetic field intensities, and we further consider the change in magnetic field intensity due to the induced eddy current, which also increases the accuracy of the magnetic noise calculation. For extremely low frequencies below 20 Hz, the improved noise simulation model differs from the measured results by less than 11%. If the loss separation is not considered, the difference between the measured value and the simulated value would be as high as 54%. The high agreement between the calculation and the experimental results proves the accuracy of the proposed method. Our method can be used in the design and optimization of low-noise magnetic shields to improve the sensitivity of atomic devices

Image captioning is an extremely challenging work, which involves both computer vision and natural language processing. However, in recent years, with the introduction and improvement of various new technologies, it has made a great advancement. In this paper, a novel attention-based image caption model is proposed. We use Resnet harnessed by outstanding performance in convolutional neural network, as the encoder. For the decoding, LSTM network equipping with fitness of dealing with problems highly related to time series, is adopted. At each time step, the attention mechanism guides the language model to synthesize context vectors adaptively. The experimental results show that the model has good performance in various quantitative metrics as well as in human evaluation.

The alkali-metal density ratio is one of the primary design parameters in hybrid optical pumping magnetometers. Here, experiments were conducted with a hybrid optically-pumped atomic magnetometer using a cell containing potassium and rubidium. Potassium atoms are pumped by a laser and become polarized. Rubidium atoms are polarized via collisions with potassium atoms and can be probed. The light shift was eliminated by adjusting the density ratio of potassium to rubidium atoms and by optimizing the pump laser parameters. The effect of fluctuations in the laser power and frequency were minimized as a result. The optimal density ratio and magnetic field sensitivity were 1:277 and 0.68 fT Hz−1/2, respectively.

The structure, dielectric, ferroelectric property and high-temperature dielectric relaxation behaviors (HTRBs) were systematically studied for the first time in the Ba(Hf x Ti1−x )O3 ferroelectric ceramics. It was noted that the T C of the Ba(Hf x Ti1−x )O3 ceramics decreases, while T O and T R increases with the increase of Hf quantity. Furthermore, the HTRBs were observed in all samples. Mechanisms of HTRBs were studied from complex impedance and ac conductivity, exposing that it was concerned with the drifting of oxygen vacancies (OVAs). Based on the value of theoretical calculation for activation energy, it was concluded that the HTRBs were attributed to the short distance hopping of the OVAs and the conduction was ascribed to the long-range move of doubly-ionized OVAs in Ba(Hf x Ti1−x )O3 system. Meanwhile, electron paramagnetic resonance spectra were measured to detect the defects in BHTO ceramics. The results showed that the OVAs-related defect signals were observed at g = 1.942. In addition, the dielectric constant peak of relaxation could be significantly restrained by O2 annealing. This further proved that the HTRBs being associated with the defect of oxygen.

Efficient delivery of nanoparticles into specific cell interiors is of great importance in biomedicine. Recently, the pH-responsive micelle has emerged as one potential nanocarrier to realize such purpose since there exist obvious pH differences between normal tissues and tumors. Herein, by using dissipative particle dynamics simulation, we investigate the interaction of the pH-sensitive triblock copolymer micelles composed of ligand (L), hydrophobic block (C) and polyelectrolyte block (P) with cell membrane. It is found that the structure rearrangement of the micelle can facilitate its penetration into the lower leaflet of the bilayer. However, when the ligand-receptor specific interaction is weak, the micelles may just fuse with the upper leaflet of the bilayer. Moreover, the ionization degree of polyelectrolyte block and the length of hydrophobic block also play a vital role in the penetration efficiency. Further, when the sequence of the L, P, C beads in the copolymers is changed, the translocation pathways of the micelles may change from direct penetration to Janus engulfment. The present study reveals the relationship between the molecular structure of the copolymer and the uptake of the pH-sensitive micelles, which may give some significant insights into the experimental design of responsive micellar nanocarriers for highly efficient cellular delivery.

We present an ultrahigh-sensitivity electro-optic modulator (EOM) detection method for detecting the atomic Larmor precession in an all-optical K–Rb hybrid atomic magnetometer operating in the spin-exchange relaxation-free regime. A magnetic field sensitivity of ~10 f T Hz−1/2 has been achieved by optimizing the probe laser parameters and the EOM modulation conditions, which is comparable to that with the Faraday modulation method and has a better performance than the balanced polarimetry method in the low frequency range. The EOM detection method in the atomic magnetometer presents several advantages, such as simple structure, no extra magnetic noise, moderate thermal effect, high measurement sensitivity and reliable stability. It is demonstrated to be feasible for the improved compactness and simplicity of atomic magnetic field measurement devices in the future.

The property of σ-meson or f0 (400-1200) is studied in the general color symmetry model (GCM) for quantum chromodynamics. With recent determined values of mσ, fσ and fπ in GCM, the isoscalar ππ S-wave amplitude is calculated without any free parameter. The T-matrix pole for f0 (400-1200) is found to be 1011- i 284 MeV, which is very close to the Particle Data Group value (400-1200)-i (300-500) MeV.

We investigate the electron transport and conductance properties in Fibonacci quasi-periodic graphene superlattices with electrostatic barriers and magnetic vector potentials. It is found that a new Dirac point appears in the band structure of graphene superlattice and the position of the Dirac point is exactly located at the energy corresponding to the zero-averaged wave number. The magnetic and electric potentials modify the energy band structure and transmission spectrum in entirely diverse ways. In addition, the angular-dependent transmission is blocked by the potential barriers at certain incident angles due to the appearance of the evanescent states. The effects of lattice constants and different potentials on angular-averaged conductance are also discussed.

In a K-Rb-21Ne co-magnetometer, the Rb electron magnetic field which is experienced by the nuclear spin is about 100 times larger than that of the K in a K-3He co-magnetometer. The large electron magnetic field which is neglected in the K-3He co-magnetometer coupled Bloch equations model is considered here in the K-Rb-21Ne co-magnetometer to study the low frequency magnetic field suppression effect. Theoretical analysis and experimental results shows that in the K-Rb-21Ne spin co-magnetometer, not only the nuclear spin but also the large electron spin magnetic field compensate the external magnetic field noise. By comparison, only the 3He nuclear spins mainly compensate the external magnetic field noise in a K-3He co-magnetometer. With this study, in addition to just increasing the magnetic field of the nuclear spins, we can suppress the magnetic field noise by increasing the density of the electron spin. We also studied how the magnetic field suppression effect relates to the scale factor of the K-Rb-21Ne co-magnetometer and we compared the scale factor with that of the K-3He co-magnetometer. Lastly, we show the sensitivity of our co-magnetometer. The magnetic field noise, the air density fluctuation noise and pumping power optimization are studied to improve the sensitivity of the co-magnetometer.

Phase change material microcapsules (MicroPCMs) were synthesized by a coreshell-like emulsion polymerization method. Styrene and methylacrylic acid copolymer (PS- MAA) was used as a wall material, and paraffin was used as a core material in order to prepare spherical, high resistance and high enthalpy MicroPCMs. Scanning Electron Microscope (SEM), laser particle size analyzer, Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetry (TG) and Differential Scanning Calorimeter (DSC) were employed to characterize the MicroPCMs. The results indicated that the average particle size of MicroPCMs was 42.29 μm, and the content of paraffin within microcapsules was 57.6%. The melting temperature and crystallization temperature were 30.7°C and 25.2°C.The melting enthalpy and crystallization enthalpy were -84.1 J/g and 91.3 J/g, respectively.

In this paper, we demonstrate an enhancement to SPW cavity through the incorporation of high-Q WGM bottle microresonator (BMR) with surface microgrooves. A standard BMR fabricated through the "soften-and-compress" technique with initial length of 280 μm, bottle diameter of 187 μm and stem diameter of 125 μm was utilized in the experiment for supporting WGMs. Thin gold film was deposited on top of the BMR for generating SPWs. 21 microgrooves was then inscribed on the metal surface of the BMR along the azimuthal direction with 10 μm length, 485 nm width, 6 μm depth and pitch of 1.5 μm. Due to surface curvature, the gold film only covered half of the BMR with a characteristic meniscus shape and maximum thickness of 30 nm. The meniscus provides appropriately tapered metal edges that facilitate the adiabatic transformation of BMR WGMs to SPWs and vice-versa. Lorentzian shape-line fit performed on the TM excited resonances show that plasmonic Q values in excess of 4000 could be achieved from such structure with ~ 25% coupling efficiency.