In Press
In Press catalogue
- Vol.73 No.19
2024-10-05
2024, 73 (19): 190501.
Abstract +
The fine structure of multi-compartment neurons can simultaneously capture both temporal and spatial characteristics, offering rich responses and intrinsic mechanisms. However, current studies of the effects of channel blockage and noise on neuronal response states are mainly limited to single-compartment neurons. This study introduces an analytical method to explore theintrinsic mechanism of channel blockage and noise effects on the response states of multi-compartment neurons, by using the smooth Pinsky-Rinzel two-compartment neuron model as a case study. Potassium, sodium, and calcium ion channel blockage coefficient are separately introduced to develop a smooth Pinsky-Rinzel neuron model with ion channel blockage. Methods such as single-parameter bifurcation analysis, double-parameter bifurcation analysis, coefficient of variation, and frequency characteristics analysis are utilized to examine the effects of various ion channel blockages on neuronal response states. Additionally, smooth Pinsky-Rinzel neuron Subunit noise model and conductance noise model are constructed to investigate their response characteristics by using interspike interval analysis and coefficient of variation indicators. Subthreshold stimulation is used to explore the presence of stochastic resonance phenomena. Single-parameter bifurcation analysis of the ion channel blockage model elucidates the dynamic processes of two torus bifurcations and limit point bifurcations in Pinsky-Rinzel neuron firing under potassium ion blocking. Double-parameter bifurcation analysis reveals a nearly linear increase in the Hopf bifurcation node of potassium ions with input current, whereas sodium ions exhibit a two-stage pattern of linear decline followed by exponential rise. The analysis of average firing frequency and coefficient of variation indicates that the moderate potassium channel blockage promotes firing, sodium channel blockage inhibits firing, and calcium channel blockage shows the complex characteristics but mainly promotes firing. Subthreshold stimulation of the channel noise model demonstrates the stochastic resonance phenomena in both models, accompanied by more intense chaotic firing, highlighting the positive role of noise in neural signal transmission. The interspike interval and coefficient of variation indicators show consistent variation levels for both noise models, with the conductance model displaying greater sensitivity to membrane area and stronger encoding capabilities. This study analyzes the general frequency characteristics of potassium and sodium ions in a multi-compartment neuron model through ion channel blocking model, providing special insights into the unique role of calcium ions. Further, the study explores stochastic resonance by using ion channel noise model, supporting the theory of noise-enhanced signal processing and offering new perspectives and tools for future studying complex information encoding in neural systems. By constructing an ion channel blockage model, the effects of potassium and sodium ions on the frequency characteristics of multi-compartment neurons are analyzed and the special influences of calcium ions are revealed. Using the ion channel noise model, the stochastic resonance is investigated, supporting the theory that the noise enhances signal processing. This research offers a new perspective and tool for studying the complex information encoding in neural systems.
2024, 73 (19): 190701.
Abstract +
At present, high-precision digital thermometers based on industrial platinum resistance have become a popular research direction and are widely used in environmental monitoring, medical health, industrial automation and other fields. However, due to the influence of materials and manufacturing processes, the measurement accuracy is average. With the increase of service life, it is inevitable that the temperature measurement deviation will be caused by the drift of the resistance value. The algorithm of correcting temperature is an effective method to improve the measurement accuracy of digital thermometers. Traditional compensation function correction algorithms such as polynomial fitting and B-spline fitting have good correction effect, but the problems of resistance drift cannot be solved. The segmented linear correction algorithm is simple and easy to implemente, but it requires multi-point temperature measurements. Because of the nonlinear changes of the temperature correction curve, the correction effect is average, which limits its correction accuracy and universality. Therefore, we proposenalgorithm of reconstructing temperature correction curve based on the pseudo inverse method. Firstly, the reconstruction matrix is built by using the original data and multiple characteristic temperature points. Then, the complete temperature correction curve is reconstructed by the characteristic temperature points to be reconstructed and the reconstruction matrix. Finally, the reconstructed temperature correction curve is automatically included in the sample database, which improves the diversity of samples and the correction accuracy of the algorithm. Experimental results show that the proposed algorithm has a better correction effect on nonlinear changes and drifts of the temperature correction curve. And the proposed algorithm is less affected by the number of characteristic temperature points and the selection combination. The complete temperature correction curve is well reconstructed by collecting only 4 characteristic temperature points. Therefore, the proposed algorithm can provide the effective support for improving the measurement accuracy of digital thermometer.
2024, 73 (19): 190702.
Abstract +
GeTe belongs to a chalcogenide phase change material, which can dynamically achieve reversible switching between the crystalline state of low resistivity and the amorphous state of high resistivity by utilizing the thermally induced phase change characteristics. The GeTe is an important functional material in the fields of memristors and nonvolatile radio frequency (RF) switches. For RF switch applications, this paper focuses on optimizing the electrical performance of GeTe thin films prepared by magnetron sputtering. By comprehensively analyzing the effects of substrate materials, sputtering conditions, and annealing conditions on the resistivity of crystalline GeTe films, effective conditions for preparing low resistivity GeTe films are explored. Fig. (a) shows that compared with the GeTe film on a SiO2substrate, the film on an Al2O3substrate can obtain higher crystallinity and lower resistivity. For the deposition power and pressure shown in Fig. (b), the combination of medium power (50–80 W) and low pressure (2–3 mTorr) is beneficial for low crystalline resistivity of GeTe film. Additionally, Fig. (c) shows that higher annealing temperature (350–400 ℃) can realize lower film resistivity. Finally, the experimental results show that the lowest crystalline resistivity of the prepared GeTe thin film reaches 3.6×10–6Ω·m, and the resistance ratio is more than 106. Based on rectangular chips of GeTe film, a parallel millimeter-wave switch with zero static power is also constructed. As shown in Fig. (d), the insertion loss is less than 2.4 dB, and the isolation is greater than 19 dB in a 1–40 GHz frequency band, demonstrating the potential application of GeTe thin films in the field of broadband high-performance discrete nonvolatile RF switches.
2024, 73 (19): 190703.
Abstract +
The Hefei Advanced Light Facility is the fourth-generation diffraction-limited storage ring light source, scheduled to begin operation in 2028. With its high-brightness and highly coherent X-rays, it will break through the current spatiotemporal resolution bottlenecks of X-ray techniques in studying correlated electron systems, providing crucial information for understanding the nature and microscopic origins of novel physical properties in these materials. This article introduces the main scientific goals and technical advantages of the Hefei Advanced Light Facility, focusing on the application perspectives of advanced technologies such as angle-resolved photoemission spectroscopy, magnetic circular dichroism, coherent X-ray scattering, and coherent X-ray imaging in researches of quantum materials and correlated electron systems. These techniques will enable the detailed analysis of the distribution and dynamics of electronic/spin/orbital states, reveal various novel quantum phenomena, and elucidate the fluctuations of order parameters in correlated electron systems. The completion of the Hefei Advanced Light Facility will provide advanced technical supports for decoding complex quantum states and non-equilibrium properties, ultimately promoting the application of quantum materials and correlated electron systems in frontier fields such as energy and information.
2024, 73 (19): 193201.
Abstract +
Cocrystals represent an effective method to manipulate the physicochemical properties of materials at a molecular level. However, understanding the relationship between their complex crystal structures and macroscopic properties is a challenge. In this paper, by using terahertz (THz) spectroscopy to characterize non-covalent interactions within crystals, the THz vibrational spectra of the CL-20/MTNP cocrystal are studied. Firstly, the THz spectra of CL-20, MTNP, and the CL-20/MTNP cocrystal are measured at room temperature. Both absorption positions and intensities of the cocrystals differ from those of their original components, confirming the unique advantage of terahertz spectroscopy in cocrystal identification. Secondly, the THz vibrational features of the three materials are calculated based on density functional theory (DFT). Then, the experimental absorptions are matched with the calculated vibrations. Furthermore, a vibrational decomposition method is employed to decompose the molecular vibrations into intermolecular and intramolecular vibrations. The vibrational variations of the cocrystal compared with its original components are analyzed. The results reveal that in the cocrystal, the intermolecular vibrational modes of both CL-20 and MTNP molecules have changed compared with their raw materials. This indicates that the non-covalent interactions in the cocrystal have changed the original intermolecular interactions of these molecules. Consequently, this enhancement promotes the heat transfer between MTNP and CL-20 molecules, thereby improving the thermal stability of the cocrystal. These findings in this study demonstrate that the THz vibrational spectroscopy technology helps establish a relationship between the molecular structure of cocrystal and its macroscopic properties. This research contributes to deepening our understanding of cocrystal systems and opens up a new way for designing and optimizing materials.
2024, 73 (19): 193601.
Abstract +
Rare earth doped boron clusters have attracted much attention due to their special optical, electrical and magnetic properties. The geometric structures, stability, electronic properties and aromaticity of negative rare earth doped boron clusters
$ {\text{REB}}_n^ - $
(RE = La, Sc;n= 6, 8) are investigated with the artificial bee colony algorithm combined with density functional theory calculations at the PBE0/RE/SDD//B/6-311+G* level of theory. Calculations show that the ground state structures of
$ {\text{REB}}_n^ - $
(RE = La, Sc;n= 6, 8) are all ofC2symmetry, and the doped lanthanide atom is located in a “boat-shaped” structure at the top center. By comparing with the experimental photoelectron spectra, it is confirmed that the ground state structure of
$ {\text{LaB}}_{8}^ - $
is a “zither-like” three-dimensional structure, and the ground state structure of
$ {\text{ScB}}_{8}^ - $
is an “umbrella” structure withC7Vsymmetry formed by the scandium atom at the “umbrella handle”. The electron localization between RE—B is not as good as that between B—B. The simulated photoelectron spectra have similar spectral characteristics to the experimental results. The lowest energy structures of
$ {\text{LaB}}_{6}^ - $
and
$ {\text{ScB}}_{6}^ - $
areσ-π double aromatic clusters, and the structures exhibit aromaticity. The density of states of low-energy isomers shows that the open shell
$ {\text{ScB}}_{8}^ - $
density of states spectrum exhibits spin polarization phenomenon, which is expected to assemble magnetic material components. These studies contribute to understanding the evolution of structure and properties of nanomaterials, and provide important theoretical support for designing nanomaterials with practical value.
2024, 73 (19): 194101.
Abstract +
2024, 73 (19): 194201.
Abstract +
With the development of ultrafast science and attosecond laser technology, the pump-probe system based on isolated attosecond laser pulses is a key to attosecond science, which will be used to study electronic dynamics on an attosecond time-scale. To obtain stable and reliable signals, it is necessary to ensure ultra-stable and ultra-accurate synchronization. Any timing jitter can cause signal to disperse or get buryied in noise, making it impossible to obtain the true physical mechanism. Based on the above, the delay between pump laser pulse and probe laser pulse must be controlled with an attosecond time resolution. In this work, a dual-layer system is developed to achieve high-precision synchronization locking. To ensure that both layers have the same time jitter, we design an adapter to secure the elements placed during installation. Timing jitter is obtained by shaking interference fringes through fast Fourier transformation, and can be calculated in several ms. Then error signals are fed back to the PZT stage in order to compensate for real-time optical path drift. Through such a design, a time-delay accuracy of 7.64 as to 15.53 as is realized, which is linearly related to the interferometer arm length ranging from 1 m to 5 m, with anR2of 0.96. Moreover, the error between the experimental result of arm length of 8 m and 10 m and the result fitted with the above data is less than 3 as. These results show that using a small interferometer can achieve the fast detection of the time-delay accuracy of long-arm attosecond pump-probe detection system in large scientific instrument, which is of great significance in guiding ther applications such as in non-collinear attosecond streaking spectroscopy, time-resolved photoelectron spectroscopy, and coherent synthesis.
2024, 73 (19): 195201.
Abstract +
When an intense laser obliquely irradiates a solid, a pre-pulse will first ionize the solid surface, followed by the main pulse interacting with the plasma and ultimately being reflected by the plasma. Simultaneously, certain electrons within the plasma will be trapped in the accelerating phase of the laser field, subsequently gaining effective acceleration within the field, this phenomenon is known as phase-locked electron acceleration. Given the current intense lasers' electric field intensity nearing the TV/m range, electrons could potentially acquire energy levels on the order of hundreds of GeV or even TeV, provided they stay in the accelerating phase of the laser field long enough. Here, we initially use PIC (Particle-in-Cell) simulations to simulate the interaction process between laser pulses and plasma, thereby obtaining the properties of phase-locked electrons. In order to reduce computational demands, we turn to use a three-dimensional (3D) test particle model to calculate the subsequent interactions of these electrons with the reflected laser field. By this model, we obtain the data of the locked-phase electrons after having interacted with the reflected laser (Fig. (a)). Furthermore, we use this model to calculate the dynamical behavior of electrons under different initial conditions (Fig. (b)). Under the laser intensity of
$ {a}_{0}=350 $
(
$ {a}_{0} $
is the normalized laser vector potential), the energy of the electrons directly accelerated by the laser is enhanced to 32 GeV. In contrast, under the same laser intensity, the energy of the electrons accelerated by ponderomotive force is only 0.35 GeV. The research findings indicate that the strong laser with peak power around 10 PW can directly accelerate electrons to approximately 30 GeV. Additionally, this study outlines the optimal initial conditions for injecting electrons into the laser field and the final electron energy within the phase-locked acceleration mechanism, thereby establishing a calibration relationship with the laser field intensity. Given the continual enhancement of laser intensity and the potential application of the laser phase-locked electron acceleration mechanism to positron acceleration, this research holds promise for its implementation in fields such as miniaturized positron-electron colliders and high-energy gamma-ray sources.
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