Coherence Transition Research Articles

Observation of the Granular Josephson Mechanism and the Vortex-Glass Transition in the Polycrystalline GdBa2Cu3O7- δ Superconductor

The resistive transition between the normal and superconducting states in high critical temperature superconducting materials is characterized by the occurrence of two well-defined stages: a transition in the higher temperature thermal region called pairing transition and another known as coherence transition. In the presence of low magnetic fields, in the first transition, it is possible to identify a genuinely critical fluctuation regime, with Gaussian regimes. The Aslamazov-Larkin model in the 3D regime allows to analyze the amplitude of the order parameter, leading to the determination of parameters such as coherence length and critical field. In the coherence transition, the phase of the order parameter is the relevant quantity that varies between the grains of the system, leading to Josephson-type effects in the intergranular barriers due to the polycrystalline feature of this family of materials. The coherence transition for the sample GdBa2Cu3O7-δ under the application of seven different electric transport currents was studied in this work. The sample was produced by the solid-state reaction and the resistive behavior was determined to perform the paraconductivity analysis and characterizes granularity effects on the superconducting order parameter. A genuinely critical region characterized by dynamic critical exponent z = 4.5 was identified, similar to the value reported for the transition vortex glass – fluid. This paper proposes to identify three-dimensional Gaussian fluctuations in the paracoherent to get a coherence length associated with Josephson effects in the granular barrier and to find a factor related with the Josephson current in function of the seven applied currents.

Evaluation of Nocturnal Aerosol Optical Depth Determining From a Lunar Photometry in Lanzhou of Northwest China

AbstractA Cimel Sun‐sky‐lunar photometer (CE318‐T) is designed to perform daytime and nighttime photometric measurements and calculate diurnal cycle of aerosol optical depth (AOD). Nevertheless, the determination of nocturnal AOD from CE318‐T requires a precise knowledge of extraterrestrial lunar irradiance, which significantly changes with moon's phase angle (MPA) and lunar libration in a single night. This study evaluated the 1‐year nocturnal AODs at Lanzhou by using three different methods, which were validated by collocated measurements of DIAL Lidar (as a reference) and Cimel software (as a proxy). The results indicated that three independent approaches could implement a similar performance to compute nocturnal AOD near full moon phase (i.e., MPA = 0°) under moderate aerosol loading. The spectral AOD values at nighttime calculated by ROLO Lunar Langley (Robotic Lunar Observatory model) and Sun‐moon Gain Factor (SMGF) methods are significantly underestimated under low moon's illumination or high MPA (MPA < −47° or MPA > 47°) and distinctly dependent on MPA. The RIMO correction factor (RCF) (ROLO Implementation for Moon photometry Observation correction factor) method could compensate the underestimated extraterrestrial lunar irradiances of ROLO model for about 6.76%–9.78%, and thus greatly improve the calculation accuracy of nighttime AOD. The day/night coherence transition test has demonstrated that we would obtain a good diurnal variation of AODs at Lanzhou after RCF correction. The overall averages of nocturnal AOD440nm differences between Cimel software and ROLO model and SMGF method are 0.064 ± 0.024 and 0.052 ± 0.022, respectively, while the corresponding difference of RCF is less than 0.021 ± 0.014 for all wavelengths, falling within uncertainty range of AERONET AOD products (∼±0.02). The diurnal variations of AODs determined from RCF method agree well with synchronous results of DIAL Lidar, with total mean AOD532nm differences of 0.038 ± 0.024 and 0.023 ± 0.017 in daytime and nighttime, respectively. The spectral AODs computed from RCF method are well consistent with Cimel software, although there are some discrepancies under low AOD cases (AOD440nm < 0.30), and the overall average of AOD440nm differences are less than −0.0053 ± 0.002 and −0.0185 ± 0.013 in daytime and nighttime, respectively. Our results confirmed that the CE318‐T photometer can be reasonably calculated nighttime AOD and Ångström exponent (AE440–870nm) at urban Lanzhou by using three independent methods, although the former two need to be greatly improved under low moon's illumination. The RCF method was proved to reliably calculate nocturnal AOD from moonlight irradiance, which didn't rely on MPA. A more accurate lunar irradiance model needs to be developed to improve the underestimation of current ROLO model. Long‐term climatological information of nocturnal AOD is crucial for comprehensively characterizing the diurnal variations of aerosol optical properties and atmospheric boundary layer structure during the winter at typical northern city of China, which deserves to be further investigated in the future.

Exploring challenges and approaches for ChatGPT in multilingual and multisectoral contexts

ChatGPT, a transformer-based chatbot model, has gained significant attention for its ability to generate natural and coherent responses. However, the model still faces several challenges that limit its performance and applicability. This essay explores the current challenges of ChatGPT and proposes solutions to overcome them. The challenges identified include the scarcity of diverse and high-quality training data, coherence and topic transition issues in long conversations, and the risk of overfitting during training. To address these challenges, the essay proposes several solutions. Transfer learning techniques are suggested to improve model generalization by pre-training on a large corpus and fine-tuning on specific chatbot tasks. Regularization methods such as dropout and weight decay are recommended to prevent overfitting and improve generalization. The design of more effective evaluation metrics, including F1 score and human evaluation, is proposed to accurately assess the model's performance. Additionally, incorporating contextual information from previous conversation turns is explored to enhance coherence.The proposed solutions are evaluated through experiments and benchmarking. The results demonstrate promising improvements in the performance of ChatGPT, including enhanced coherence, better topic transition, reduced overfitting, and higher-quality generated responses. This research contributes to the advancement of chatbot models by addressing the challenges faced by ChatGPT. The proposed solutions offer practical strategies to improve the model's performance and applicability in real-world scenarios. The findings have implications for various industries that rely on chatbot technology, enabling them to provide more natural and coherent interactions with users.

Undergraduate Students’ Writer’s Block in English as an Academic Language: Causes, Coping Strategies Needs

This study aims to explore writer’s block in the tertiary education context and draws from 644 senior English language and literature students’ self-reports on producing academic texts in English. A mixed-methods survey design was used to collect data from the participants. Findings showed that both internal and external causes of writer’s block were at work, yet external causes were moderately more influential, while students produced argumentative-critical and expository essays and were influential in the drafting stage of the writing process. Findings also revealed that students pursued continue-to-write and avoid-writing strategies in different combinations to cope with writer’s block and needed to expand their knowledge and experience in drafting, planning, using academic language, coherence, and smooth transitions between sentences and paragraphs. Lastly, findings highlighted the need for clear instructions, studying sample texts, and feedback from teachers to overcome writer’s block. In light of these findings, several pedagogical implications were suggested.

Renormalization of steered coherence and quantum phase transitions in the alternating Ising model

We explore net steered coherence defined with respect to the mutually unbiased bases. By using the quantum renormalization group method, we studied its scaling property for the ground state of two blocks of the alternating Ising model in the renormalized space. The results show that different patterns in the net steered coherence describe different phases of the model, and its susceptibility with respect to the magnetic field is divergent at the critical points of quantum phase transitions. As the net steered coherence exists for almost all bipartite states, it can serve as an alternative for exploring quantum criticality of the many-body systems in the parameter regions without entanglement and quantum discord.

Graphop mean-field limits and synchronization for the stochastic Kuramoto model

Models of coupled oscillator networks play an important role in describing collective synchronization dynamics in biological and technological systems. The Kuramoto model describes oscillator's phase evolution and explains the transition from incoherent to coherent oscillations under simplifying assumptions, including all-to-all coupling with uniform strength. Real world networks, however, often display heterogeneous connectivity and coupling weights that influence the critical threshold for this transition. We formulate a general mean-field theory (Vlasov-Focker Planck equation) for stochastic Kuramoto-type phase oscillator models, valid for coupling graphs/networks with heterogeneous connectivity and coupling strengths, using graphop theory in the mean-field limit. Considering symmetric odd-valued coupling functions, we mathematically prove an exact formula for the critical threshold for the incoherence-coherence transition. We numerically test the predicted threshold using large finite-size representations of the network model. For a large class of graph models, we find that the numerical tests agree very well with the predicted threshold obtained from mean-field theory. However, the prediction is more difficult in practice for graph structures that are sufficiently sparse. Our findings open future research avenues toward a deeper understanding of mean-field theories for heterogeneous systems.

Automatic Construction of Predictable and High-Performance Cache Coherence Protocols for Multicore Real-Time Systems

Predictable hardware cache coherence is a viable shared data communication mechanism between cores for multicore real-time platforms. Prior works have established that predictable hardware cache coherence protocols offer significant performance advantages over alternative predictable data communication mechanisms while ensuring predictability. Unlike alternative predictable data communication mechanisms, designing predictable cache coherence protocols is nontrivial as it requires detailed understanding of the impact of different memory activity patterns to shared data for predictable and coherent data communication. Furthermore, designing predictable cache coherence protocols that deliver high average-case performance is even more challenging as it entails identifying opportunities such that a core’s access to a data is not stalled in the presence of interleaving memory activity from other cores to the same data. To this end, we present SYNTHIA, an open and automated tool for synthesizing predictable and high-performance snooping bus-based cache coherence protocols for multicore platforms deployed in real-time systems. SYNTHIA automates the complex analysis associated with designing predictable and high-performance cache coherence protocols, and constructs the complete protocol implementation (coherence states and transitions) that achieve predictability and performance. We use SYNTHIA to construct complete protocol implementations from simple specifications of common protocols (modified-shared-invalid (MSI), MESI, and MOESI protocols) and a predictable variant of the MESIF cache coherence protocol, which was recently found to be deployed in an existing multicore platform designed for real-time platforms. We validated the correctness, predictability, and performance guarantees of the generated protocol implementations from SYNTHIA using manually implemented versions, and a micro-architectural simulator.

Time‐Resolved Second‐Order Coherence Characterization of Broadband Metallic Nanolasers

AbstractHigh‐bandwidth metallic coaxial nanolasers are of high interest to investigate laser physics such as thresholdless coherence transitions, and have a large variety of promising applications enabled by their ultrasmall size and large spectral bandwidth. Optical coherence properties are commonly characterized in Hanbury‐Brown and Twiss experiments. However, those are difficult to perform in broadband lasers when the coherence time is an order of magnitude shorter than the temporal resolution of the single‐photon detectors, thus requiring significant spectral filtering. This paper demonstrates a new approach in investigating the temporal dynamics of the photon statistics associated with the nanolaser emission, obtained without the requirement of spectral filtering. While optically pumping the nanolasers with nanosecond pulses, time‐resolved second‐order coherence properties are evaluated over the time duration of the pump pulse. Coherence transitions from thermal emission to lasing are observed in the gathered time‐resolved photon statistics, linked to the temporal change in optical power of the nanosecond pump pulses. As nanolasers show better performance for the pulsed pumping scheme, the temporal envelope modulation of these pulses results in varying degrees of coherence within the nanolaser pulse envelope. This approach can also be readily applied to characterize a large variety of broadband lasers.

Quantum coherence and ground-state phase transition in a four-chain Bose–Hubbard model

We study the quantum coherence and ground-state phase transition of a four-chain Bose–Hubbard model with the long-range interaction. In a special four-chain Bose–Hubbard model, i.e., each chain only has one optical potential, four types of the ground-state phases are discovered. The effects of the disorder, the on-site interaction and the long-range interaction on the quantum coherence are studied. For the system without the long-range interaction, the quantum coherence changes from one periodic oscillation to two periodic oscillations as the on-site interaction increases. By considering the long-range interaction, the quantum coherence goes back to one periodic oscillation again. The on-site interaction itself suppresses the quantum coherence, both the on-site interaction and long-range interaction together enhance the quantum coherence with the weak disorder. If the disorder strength is increased beyond a critical value, they start to suppress the quantum coherence. In a regular four-chain Bose–Hubbard model, i.e., each chain has many optical potentials, the ground-state phase transitions are obtained by using the cluster Gutzwiller mean-field method. Exotic ground-state phases are found, i.e., superfluid phase, integer Mott insulator phase, supersolid phase and loophole insulator phase. The combination of the loophole insulator phase and the supersolid phase expands the lobes with the half-integer filling per site for the small ratio β = t ∥/t ⊥.

Coherence length versus transition temperature of hydride-based and room temperature superconductors

Recent discoveries of carbon-sulfur-hydrogen (C-S-H) room temperature superconductor (287.7 K) and near room temperature in hydride-based materials under high pressure have opened up an interesting and new avenue in the field of superconductivity. One of the important parameters of a superconductor is the coherence length, ξ which is the variation in the density of superconducting phase. ξ can also be related to the characteristic Cooper pair size. In this paper we report on the relation between ξ and the transition temperature, Tc of heavy fermions, conventional, iron arsenide-, cuprate- and hydride-based superconductors. This work showed that the coherence length was large for low Tc but for high Tc, ξ is short and tends to reach saturation value between 15 and 30 Å. ξ of the newly discovered hydride superconductors was found to be in the range of the cuprates. In this work, the coherence length of a 300 K superconductor extrapolated from the hydride-based data was found to be around 15 Å. This coherence length is sufficiently large to allow an effective Coulombic attraction between electrons in a Cooper pair.

Coherence and Quantum Phase Transition in Spin Models

Based on quantum renormalization group (QRG) method, we investigated quantum coherence and quantum phase transition (QPT) in XXZ chain and XY chain, respectively. The results show that both the geometric quantum coherence and entropic coherecne can accurately indicate the QPT at critical point after enough iteration steps. Moreover, the increasing anisotropy parameter destroys the coherence in the XXZ chain, while enhances it in the XY chain. In addition, focused on the XXZ chain we analyzed the nonanalytic phenomena and scaling behaviors with different theoretical exponents in detail.

Quantum coherence and topological quantum phase transitions in the extended XY chain

We study the quantum criticality of single- and two-spin coherence, based on the quantum skew information, in the extended XY model, and analyze the impact of different driving parameters, finite temperatures and site distances of spin-pair on their critical behaviors. We find that the first-order derivative of quantum coherence can correctly detect the topological quantum phase transitions (TQPTs), but the finite temperatures strongly affect the accuracy of detection for critical points. For the case of long-distance spin-pairs, we find that the quantum coherence is a long-range correlation and its first-order derivative can also correctly detect the TQPTs at the absolute zero temperature. Moreover, the quantum coherence itself under absolute zero temperature can also signal the partial TQPTs by a local extrema in several certain situations.

Renormalization of quantum coherence and quantum phase transition in the Ising model

Quantifying quantum coherence of a given system not only plays an important role in quantum information science but also promotes our understanding of some basic problems, such as quantum phase transition. Conventional quantum coherence measures, such as l1-norm of coherence and relative entropy of coherence, are widely used to study quantum phase transition. Here we adopt a basis-independent coherence measure that is a quantum version of the Jensen–Shannon divergence to investigate the property of total quantum coherence, as well as its two contributions in quantum critical systems. Based on the quantum renormalization group method, we propose an analysis of the distribution of quantum coherence in the Ising system near the quantum critical point. We directly obtain the tradeoff relation, singular property, and scaling behavior in the Ising system. Furthermore, the monogamy relation is also studied in detail. These results further expand our understanding of quantum coherence as well as to enlarge the applications in using quantum coherence to reflect quantum critical phenomena.

A Study of Electrical Magnetoconductivity Paracoherent Transition of Granular YBCO Doped Superconductors: A Possible Evidence of an Inverted XY Transition

This communication reports an electrical magnetoconductivity fluctuation study in polycrystalline (granular) samples of YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.985</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.015</sub> O <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathrm {7-\delta}}$ </tex-math></inline-formula> and YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.75</sub> Sr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.25</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathrm {7-\delta }}$ </tex-math></inline-formula> superconductors. The measurements were performed in magnetic fields <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H \le1000$ </tex-math></inline-formula> Oe applied parallel to the measurement density current. The samples were prepared by a standard solid-state reaction technique. The results were analyzed in terms of the temperature derivative of the electrical resistivity, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d\rho $ </tex-math></inline-formula> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">/dT</i> , and of the inverse of the logarithmic derivative of the electrical conductivity with respect to temperature, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\chi _{\sigma }^{-1}(T)$ </tex-math></inline-formula> . The results allowed the identification of power law divergences of the magnetoconductivity and show that the superconductivity transition in our samples is a two-stage process. The genuine superconductor state with zero resistance stabilizes at the coherence transition temperature, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{\mathrm {C0}}$ </tex-math></inline-formula> , in which a long-range-ordered state for the phase of the order parameter is established in the whole granular array. The approach to the zero-resistance state is characterized by the critical exponent <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda \sim ~3.5$ </tex-math></inline-formula> for our Sr doped sample and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda \sim ~4$ </tex-math></inline-formula> for our Fe doped sample. It indicates that the universality class for the coherence transition for our samples is that of the 3-D XY model where non-trivial disorder is relevant. At a temperature called <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{\mathrm {C}}^{\mathrm {IN}}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{\mathrm {C}}^{\mathrm {IN}} &gt; T_{\mathrm {C0}}$ </tex-math></inline-formula> ), we observed another exponent, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda ^{\mathrm {IN}} ~ \sim ~1.4$ </tex-math></inline-formula> , which suggests a crossover in the critical phenomenology dynamic nearby the coherence transition. The origin of this crossover may be related to a change in the universality class of the transition and the value of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda ^{\mathrm {IN}}$ </tex-math></inline-formula> is consistent with a true asymptotic inverted XY critical regime. The chemical doping generally enhances the YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathrm {7-\delta }}$ </tex-math></inline-formula> superconductor granular character; however, its physical contribution to the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda ^{\mathrm {IN}}$ </tex-math></inline-formula> exponent is an open question.

Quantum coherence spectrum and quantum phase transitions

We review the internal connection between quantum coherence (QC) and quantum phase transitions (QPTs). We propose two quantities ${L}_{\text{QC}}$ and ${S}_{\text{QC}}$ to detect QPTs of different orders by analyzing the spectrum of QC. Our results show that the two quantities not only can detect different types of QPT but can also exhibit a remarkable robustness against thermal fluctuations. In comparison with other detectors, such as quantum entanglement and QD, ${L}_{\text{QC}}$ and ${S}_{\text{QC}}$ can show more effective and reliable behaviors in characterizing a QPT at zero and finite temperatures. In light of this property and the fundamental role of QC in quantum information processing, QC spectrum-related ${L}_{\text{QC}}$ and ${S}_{\text{QC}}$ have considerable importance in detecting QPTs at a real finite-temperature experimental environment.

Novel Light Weight Compressed Data Aggregation using sparse measurements for IoT networks

Optimal data aggregation aimed at maximizing IoT network lifetime by minimizing constrained on-board resource utilization continues to be a challenging task. The existing data aggregation methods have proven that compressed sensing is promising for data aggregation. However, they compromise either on energy efficiency or recovery fidelity and require complex on-node computations. In this paper, we propose a novel Light Weight Compressed Data Aggregation (LWCDA) algorithm that randomly divides the entire network into non-overlapping clusters for data aggregation. The random non-overlapping clustering offers two important advantages: 1) energy efficiency, as each node has to send its measurement only to its cluster head, 2) highly sparse measurement matrix, which leads to a practically implementable framework with low complexity. We analyze the properties of our measurement matrix using restricted isometry property, the associated coherence and phase transition. Through extensive simulations on practical data, we show that the measurement matrix can reconstruct data with high fidelity. Further, we demonstrate that the LWCDA algorithm reduces transmission cost significantly against baseline approaches, implying thereby the enhancement of the network lifetime.

Detuning-induced stimulated Raman adiabatic passage in dense two-level systems

We investigate the coherence generation in dense two-level systems under detuning-induced stimulated Raman adiabatic passage (D-STIRAP). In the dense two-level system, the near dipole–dipole (NDD) interaction should be taken into consideration. With the increase in the strength of the NDD interaction, it is found that a switchlike transition of the generated coherence from maximum value to zero appears. Meanwhile, the adiabatic condition of the D-STIRAP is destroyed in the presence of the NDD interaction. In order to avoid the sudden decrease in the generated coherence and maintain the maximum value, we can use stronger detuning pulse or pump pulse, between which increasing the intensity of the detuning pulse is of more efficiency. Except for taking advantage of such maximum coherence in the high density case into areas like enhancing the four-wave mixing process, we also point out that the phenomenon of the coherence transition can be applied as an optical switch.

Temporal Coherence Transitions Induced by Channel Noise in Scale-Free Neuronal Networks with Time Delay

In this paper, we study the effect of channel noise on the temporal coherence of scale-free Hodgkin–Huxley neuronal networks with time delay. It is found that the temporal coherence of the neuronal networks changes as channel noise intensity is varied in different ways depending on the range of channel noise intensity. The temporal coherence monotonically decreases with the increase of channel noise intensity for too small or too big channel noise intensity. However, for intermediate channel noise intensity it intermittently and rapidly becomes high and low as channel noise intensity is varied, exhibiting temporal coherence transitions. Moreover, this phenomenon is dependent on coupling strength and network average degree and becomes strongest when they are optimal. This result shows that channel noise has a regulation effect on the temporal coherence of the delayed neuronal networks by inducing temporal coherence transitions. This provides a new insight into channel noise for the information processing and transmission in neural systems.

Channel noise-induced temporal coherence transitions and synchronization transitions in adaptive neuronal networks with time delay

Using spike-timing-dependent plasticity (STDP), we study the effect of channel noise on temporal coherence and synchronization of adaptive scale-free Hodgkin-Huxley neuronal networks with time delay. It is found that the spiking regularity and spatial synchronization of the neurons intermittently increase and decrease as channel noise intensity is varied, exhibiting transitions of temporal coherence and synchronization. Moreover, this phenomenon depends on time delay, STDP, and network average degree. As time delay increases, the phenomenon is weakened, however, there are optimal STDP and network average degree by which the phenomenon becomes strongest. These results show that channel noise can intermittently enhance the temporal coherence and synchronization of the delayed adaptive neuronal networks. These findings provide a new insight into channel noise for the information processing and transmission in neural systems.

An effective research for diffusion annealing temperature and activation energy in Au surface-layered Bi-2212 ceramic composites

This study tries to respond two fundamental questions such as (I) what is the role of Au inclusions in the Bi-2212 polycrystalline materials prepared at the diffusion annealing temperature of 600–850 °C on the stabilization of superconductivity in small homogeneous regions and (II) what are the diffusion coefficient and corresponding activation energy of Au inclusions for the Bi-2212 superconducting system. Solution of the former question is in association with the characteristic pairing and coherence transitions extracted from the detailed dc resistivity versus temperature measurements when the latter questions are answered by the change of sample resistivity after the removal of thin-layer from the surface with the aid of the Arrhenius relation for the first time. The experimental measurement results show that the optimum diffusion annealing temperature is observed to be 800 °C where the minor phase, local structural distortions, dislocations, lattice defects and disorders in the Bi-2212 compounds degrade considerably and reach the global minimum points. Similarly, the Josephson coupled energy resides in the maximum value, and thus the superconducting grains become more and more coupled due to the increment in the percolation of intergrains. Moreover, the diffusion coefficient of Au individuals is obtained to increase regularly from 3.6186 × 10−8 to 2.79278 × 10−7 cm2 s−1 with the enhancement in the diffusion annealing temperature. At the same time, the temperature-dependent diffusion coefficient and related activation energy values of Au are computed to be about 2.601 × 10− 6 cm2 s−1 and 1.523 eV, respectively. According to the results calculated, 1.523 eV is the required minimum activation energy for the penetration of Au (heavy metal) ions into the Bi-2212 crystal structure.