Threshold For Generation Research Articles

Combined Compression of Stimulated Brillouin Scattering and Laser–Induced Breakdown Enhanced with Sic Nanowire

In this paper, the laser pulse time compression technique, based on stimulated Brillouin scattering (SBS) and passive laser–induced breakdown (LIB) series technology, is investigated. By doping a SiC nanowire in a CCl4 solution of an LIB breakdown medium, the LIB generation threshold is reduced, and the stability of the LIB compression output is improved. When OD is 0.2, the output pulse width is 254.4 ps, and the corresponding energy conversion efficiency and pulse compression rate are 34.2% and 50.2%, respectively. Our experiment proves the feasibility of this scheme.

Enhancing conversion efficiency of MgO:PPLN and Rb:PPKTP crystal-based subnanosecond optical parametric generators by utilizing a supercontinuum seed

This paper presents an approach to enhance the conversion efficiency of subnanosecond pulse duration microlaser-pumped optical parametric generators (OPGs) tunable from near- to mid-infrared. The method involves generating a supercontinuum (SC) in the photonic crystal fiber (PCF) and using it to seed the subnanosecond OPG based on the fan-out grating design MgO:PPLN crystal. Since the SC spectrum covered the entire signal wave tuning range (1414–2128 nm), seeding and conversion efficiency improvement of 6%–11% was achieved for all OPG signal wavelengths, and the generation threshold was reduced up to 3 times. Such a method allows for improved energy stability, significantly increases the brightness of the OPG output radiation, and is pivotal in mitigating the risk of MgO:PPLN optical damage. The study also extended the method to successfully seed 532 nm pumped Rb-doped PPKTP crystal-based OPG with the same SC, demonstrating broad applicability and performance improvement across different parametric devices.

Role of galactic disc thickness in magnetic field generation

A large variety of galaxies have magnetic structures of lengthscales comparable with their radius. Theoretically, their existence is based on the dynamo mechanism. It is based on alpha-effect characterizing helicity of the turbulent motions and differential rotation which is connected with changing angular velocity. The field can be destroyed by turbulent diffusion, so the mechanism is threshold and can be realized only for the case when first and second effect are more intensive than the third one. Equations of magnetohydrodynamics that are used to describe the dynamo mechanism, are too difficult to be solved. So, usually different approximation taking into account details of astrophysical objects are used. As for galaxies, a thin disc approximation has been developed. It works properly for galactic objects with small half-thickness. However, as for thick discs we should take a model which uses more complicated structure of the field. Here we find the threshold for the field generation for thick astrophysical discs.

Kerr frequency comb generation in fiber Fabry-Pérot resonator: Technological locks and leveraging fiber properties

We explore fiber Fabry-Pérot (FFP) resonators, a new platform for frequency comb generation We experimentally identified mirror diffraction losses dependent on the effective area of the fiber and simulated them via Fourier optics. In the nonlinear regime, a linear stability analysis of a generalized Lugiato-Lefever equation revealed optimization of reflectivity and detuning, leading to a significant reduction in the required power threshold for comb generation compared to linear regime, and to improved energy frugality. Furthermore, controlled or exploited birefringence in various experimental settings enabled the generation of Kerr frequency combs and stimulated Brillouin lasers. In this communication we propose an overview of the practical characteristics related to the fabrication and use of these resonators.

An Improved Method for Evaluating Hydrocarbon Generation of Shale: A Case Study of the Lower Cretaceous Qingshankou Formation Shale in the Songliao Basin

AbstractBecause of the influence of hydrocarbons, especially adsorbed hydrocarbons, on the detection of cracked hydrocarbon (S2) and total organic carbon (TOC), the hydrogen index (HI)‐based hydrocarbon generation model deviates from actual practice. In this study, the shale in the first member of the Qingshankou Formation in the central depression of the Songliao Basin, where in northeastern China, was taken as the research object and a correction method for S2 and TOC was established. By correcting the experimental results of different maturity samples, the actual hydrocarbon generation model has been revealed, the differences before and after correction compared, and the evolutionary characteristics of the adsorbed hydrocarbon content were clarified. The results show that the organic matter enters the hydrocarbon generation threshold at Ro–0.5% and reaches the hydrocarbon generation peak at Ro–1.0% and that the hydrocarbon generation process ends at Ro–1.3%. The hydrocarbon generation model established based on the measured values has a ‘lag effect’ compared to actual values, and this extends the hydrocarbon generation window of organic matter and delays the hydrocarbon generation peak. With the increase of maturity, adsorbed hydrocarbon content shows the characteristics of ‘first increasing, then stabilizing, and then decreasing’, and reaches the most abundant stage at Ro of 0.9%–1.3%.

Methods of Measuring the Narrow-Band Generation Dynamics near the Generation Threshold of a Raman Fiber Laser with a Random Feedback

Methods of Measuring the Narrow-Band Generation Dynamics near the Generation Threshold of a Raman Fiber Laser with a Random Feedback

The evolutionary meaning of migraine.

Migraine's astonishing prevalence and preserved genetic background contrast with the definition of a disease and the biological meaning of experiencing recurrent, severe headache attacks is still puzzling. To provide a comprehensive explanation of the migraine evolutionary meaning, we review (i) the putative role of the autonomic nervous system in migraine attacks, (ii) the inter-ictal autonomic, functional, and metabolic signature of migraine patients, (iii) the bio-behavioral perspective of pain, and (iv) the allostatic perception of migraine chronification. Migraineurs have inter-ictal cortical hyperexcitability and metabolic dysfunction that predisposes to brain energetic imbalance. Multiple precipitating factors may lead to brain energy consumption over the migraine attack generation threshold. In response, the brain engenders adaptive, evolutionary conserved, autonomic-behavior responses through the antidromic activation of the trigeminovascular system. The sickness behavior and severe pain experienced during migraine attacks result in avoiding mental and physical activity, allowing brain energy restoration. Chronic exposure to stressors may result in an allostatic overload, leading to maladaptive chronic activation of these responses. In this bio-behavioral perspective, the chronification of migraine should be envisioned as a pathological process, whereas the migraine itself should not. Migraine has an evolutionary (Darwinian) meaning.

How did submarine volcanic eruptions interact with organic matter to favour hydrocarbon generation in the Bohai Bay Basin, China?

ABSTRACT Based on the geological and geochemical analysis of volcanic rock and their surrounding rocks, combined with palaeontological data and hydrocarbon generation thermal simulation experiments, the mechanism of the impact of volcanic eruptions on the formation of organic matter and hydrocarbon generation in the Dongying Depression is investigated. According to the results, underwater volcanic eruptions play a significant role in promoting biological eruptions and water stratification by introducing heat, minerals, and metal elements. The formation of the basalt source rock symbiotic association went through three evolutionary stages, which were underwater eruption, late eruption, and normal sedimentation. These stages have influenced the generation of hydrocarbons from organic matter in the following ways: (1) The organic acid released from the source rock dissolves the adjacent basalt, and the transitional metal elements in the basalt become activated and enter the source rock, which catalyses the hydrocarbon generation from the source rock. (2) Alteration of olivine in basalt releases hydrogen, improving hydrocarbon generation efficiency of source rock. (3) The existence of a large number of carbonates improves the hydrocarbon generation rate and efficiency of source rocks and reduces the hydrocarbon generation threshold of source rocks.

What level of renewable energy production will reduce ecological footprint without compromising trade? Evidence from Shanghai Cooperation Organization nations.

In order to decarbonize the global economy and reduce environmental degradation, it has become necessary to switch from using fossil fuels to renewable energy. However, a net zero global economy cannot be achieved without understanding the total renewable energy generation threshold and associated investment amount. This study estimates the renewable energy generation threshold to mitigate environmental degradation using data from 2003 to 2019 while focusing on Shanghai Cooperation Organization (SCO) nations. A panel fully modified model and the eight permanent nations of the SCO are employed. Our results show that while trade openness, foreign direct investment, and economic activities positively drive environmental degradation, renewable energy generation is a negative driver, and population has no relationship with environmental degradation. The threshold analysis shows that SCO nations need to increase their renewable energy generation from the current average of 2.403 to 7.737. Policy recommendation regarding how these nations can raise this money has been provided.

Targeted blockade of aberrant sodium current in a stem cell-derived neuron model of SCN3A encephalopathy.

Missense variants in SCN3A encoding the voltage-gated sodium (Na+) channel α subunit Nav1.3 are associated with SCN3A-related neurodevelopmental disorder (SCN3A-NDD), a spectrum of disease that includes epilepsy and malformation of cortical development. How genetic variation in SCN3A leads to pathology remains unclear, as prior electrophysiological work on disease-associated variants has been performed exclusively in heterologous cell systems. To further investigate the mechanisms of SCN3A-NDD pathogenesis, we used CRISPR/Cas9 gene editing to modify a control human induced pluripotent stem cell (iPSC) line to express the recurrent de novo missense variant SCN3A c.2624T>C (p.Ile875Thr). With the established Ngn2 rapid induction protocol, we generated glutamatergic forebrain-like neurons (iNeurons), which we showed to express SCN3A mRNA and Nav1.3-mediated Na+ currents. We performed detailed whole-cell patch clamp recordings to determine the effect of the SCN3A-p.Ile875Thr variant on endogenous Na+ currents in, and intrinsic excitability of, human neurons. Compared to control iNeurons, variant-expressing iNeurons exhibit markedly increased slowly-inactivating/persistent Na+ current, abnormal firing patterns with paroxysmal bursting and plateau-like potentials with action potential failure, and a hyperpolarized voltage threshold for action potential generation. We then validated these findings using a separate iPSC line generated from a patient harbouring the SCN3A-p.Ile875Thr variant compared to a corresponding CRISPR-corrected isogenic control line. Finally, we found that application of the Nav1.3-selective blocker ICA-121431 normalizes action potential threshold and aberrant firing patterns in SCN3A-p.Ile1875Thr iNeurons; in contrast, consistent with action as a Na+ channel blocker, ICA-121431 decreases excitability of control iNeurons. Our findings demonstrate that iNeurons can model the effects of genetic variation in SCN3A yet reveal a complex relationship between gain-of-function at the level of the ion channel versus impact on neuronal excitability. Given the transient expression of SCN3A in the developing human nervous system, selective blockade or suppression of Nav1.3-containing Na+ channels could represent a therapeutic approach towards SCN3A-NDD.

VLF chorus emissions modeling using EPOCH PIC code: Generation regimes and comparison with a backward wave oscillator theory

We present the results of a numerical model for VLF chorus emissions generation based on the EPOCH PIC code. The initial distribution function of energetic elections is assumed to have a finite-width step-like deformation in the velocities parallel to the geomagnetic field. This allows us to verify and generalize the analytical and numerical results obtained earlier within the framework of a backward wave oscillator model in which a sharp step feature is assumed. We show that in the presence of a sharp or smooth step, chorus emissions can be generated for realistic flux of energetic electrons even if the initial velocity distribution (without the step) is isotropic. Simulated chorus emissions behave very similarly for both sharp and finite-width steps. In particular, the generation of repetitive chirping chorus elements occurs if the coupling parameter exceeds the linear generation threshold several times. For smaller threshold excess, quasi-stationary or relaxation oscillation regimes take place. For the first time, we systematically study the dependence of the chorus emissions properties on the energetic electron distribution parameters, in particular, on the step width and the effective wave-particle coupling parameter proportional to the energetic electron flux and step height. We show that the functional dependences of the linear growth rate on the coupling parameter is the same for a smooth step gradient as those obtained for the sharp step within the framework of the backward wave oscillator model. The threshold flux of energetic electrons, above which whistler mode waves are generated, increases very fast with increasing step width. With a fixed relative step height, the threshold flux is about an order of magnitude higher for a step width of 8% than for a sharp step.

Suppression of small-scale dynamo in time-irreversible turbulence

ABSTRACT The conventional theory of small-scale magnetic field generation in a turbulent flow considers time-reversible random flows. However, real turbulent flows are known to be time irreversible: the presence of energy cascade is an intrinsic property of turbulence. We generalize the ‘standard’ model to account for the irreversibility. We show that even small time asymmetry leads to significant suppression of the dynamo effect at low magnetic Prandtl numbers, increases the generation threshold, and may even make generation impossible for any magnetic Reynolds number. We calculate the magnetic energy growth rate as a function of the parameters of the flow.

Ih current stabilizes excitability in rodent DRG neurons and reverses hyperexcitability in a nociceptive neuron model of inherited neuropathic pain.

We show here that hyperpolarization-activated current (Ih ) unexpectedly acts to inhibit the activity of dorsal root ganglion (DRG) neurons expressing WT Nav1.7, the largest inward current and primary driver of DRG neuronal firing, and hyperexcitable DRG neurons expressing a gain-of-function Nav1.7 mutation that causes inherited erythromelalgia (IEM), a human genetic model of neuropathic pain. In this study we created a kinetic model of Ih and used it, in combination with dynamic-clamp, to study Ih function in DRG neurons. We show, for the first time, that Ih increases rheobase and reduces the firing probability in small DRG neurons, and demonstrate that the amplitude of subthreshold oscillations is reduced by Ih . Our results show that Ih , due to slow gating, is not deactivated during action potentials (APs) and has a striking damping action, which reverses from depolarizing to hyperpolarizing, close to the threshold for AP generation. Moreover, we show that Ih reverses the hyperexcitability of DRG neurons expressing a gain-of-function Nav1.7 mutation that causes IEM. In the aggregate, our results show that Ih unexpectedly has strikingly different effects in DRG neurons as compared to previously- and well-studied cardiac cells. Within DRG neurons where Nav1.7 is present, Ih reduces depolarizing sodium current inflow due to enhancement of Nav1.7 channel fast inactivation and creates additional damping action by reversal of Ih direction from depolarizing to hyperpolarizing close to the threshold for AP generation. These actions of Ih limit the firing of DRG neurons expressing WT Nav1.7 and reverse the hyperexcitability of DRG neurons expressing a gain-of-function Nav1.7 mutation that causes IEM. KEY POINTS: Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, the molecular determinants of hyperpolarization-activated current (Ih ) have been characterized as a 'pain pacemaker', and thus considered to be a potential molecular target for pain therapeutics. Dorsal root ganglion (DRG) neurons express Nav1.7, a channel that is not present in central neurons or cardiac tissue. Gain-of-function mutations (GOF) of Nav1.7 identified in inherited erythromelalgia (IEM), a human genetic model of neuropathic pain, produce DRG neuron hyperexcitability, which in turn produces severe pain. We found that Ih increases rheobase and reduces firing probability in small DRG neurons expressing WT Nav1.7, and demonstrate that the amplitude of subthreshold oscillations is reduced by Ih . We also demonstrate that Ih reverses the hyperexcitability of DRG neurons expressing a GOF Nav1.7 mutation (L858H) that causes IEM. Our results show that, in contrast to cardiac cells and CNS neurons, Ih acts to stabilize DRG neuron excitability and prevents excessive firing.

South Africa's energy policy: Prioritizing competition and climate change for decarbonisation

An affordable, reliable, and renewable power supply is essential for economic recovery and to ensure the economy reaches its potential output over the long term. The policy framework needs to catch up to the market's need for (i) competition to address increasing tariffs and the widening capacity shortfall and (ii) the increased role of renewable energy to facilitate the country's energy transition. This study examines how competition and climate change have influenced policy reform and implementation in the South African energy sector, by reviewing its historical context and regulatory framework. Furthermore, the study estimates the cost of neglecting these objectives in policy formation by assessing the impact on the energy system, the economy and the environment. The lifting of the embedded generation threshold policy reform, which will support climate and competition objectives, albeit after the fact, is expected to yield economic, social and environmental benefits. This study empirically demonstrates this by utilising the E3ME model developed by Cambridge Econometrics to support the case for the ex-ante prioritising of climate and competition considerations in energy policy. While energy security should remain the primary objective, energy policy can be leveraged to promote other government objectives, such as increased market participation and decarbonisation.

Sodium channel endocytosis drives axon initial segment plasticity.

Activity-dependent plasticity of the axon initial segment (AIS) endows neurons with the ability to adapt action potential output to changes in network activity. Action potential initiation at the AIS highly depends on the clustering of voltage-gated sodium channels, but the molecular mechanisms regulating their plasticity remain largely unknown. Here, we developed genetic tools to label endogenous sodium channels and their scaffolding protein, to reveal their nanoscale organization and longitudinally image AIS plasticity in hippocampal neurons in slices and primary cultures. We find that N-methyl-d-aspartate receptor activation causes both long-term synaptic depression and rapid internalization of AIS sodium channels within minutes. The clathrin-mediated endocytosis of sodium channels at the distal AIS increases the threshold for action potential generation. These data reveal a fundamental mechanism for rapid activity-dependent AIS reorganization and suggests that plasticity of intrinsic excitability shares conserved features with synaptic plasticity.

Thrombin Generation Thresholds for Coagulation Initiation under Flow

In veins, clotting initiation displays a threshold response to flow intensity and injury size. Mathematical models can provide insights into the conditions leading to clot growth initiation under flow for specific subjects. However, it is hard to determine the thrombin generation curves that favor coagulation initiation in a fast manner, especially when considering a wide range of conditions related to flow and injury size. In this work, we propose to address this challenge by using a neural network model trained with the numerical simulations of a validated 2D model for clot formation. Our surrogate model approximates the results of the 2D simulations, reaching an accuracy of 94% on the test dataset. We used the trained artificial neural network to determine the threshold for thrombin generation parameters that alter the coagulation initiation response under varying flow speed and injury size conditions. Our model predictions show that increased levels of the endogenous thrombin potential (ETP) and peak thrombin concentration increase the likelihood of coagulation initiation, while an elevated time to peak decreases coagulation. The lag time has a small effect on coagulation initiation, especially when the injury size is small. Our surrogate model can be considered as a proof-of-concept of a tool that can be deployed to estimate the risk of bleeding in specific patients based on their Thrombin Generation Assay results.

Quantitative effect of kerogen type on the hydrocarbon generation potential of Paleogene lacustrine source rocks, Liaohe Western Depression, China

Kerogen types exert a decisive effect on the onset and capacity of hydrocarbon generation of source rocks. Lacustrine source rocks in the Liaohe Western Depression are characterized by thick deposition, high total organic carbon (TOC) content, various kerogen types, and a wide range of thermal maturity. Consequently, their hydrocarbon generation potential and resource estimation can be misinterpreted. In this study, geochemical tests, numerical analysis, hydrocarbon generation kinetics, and basin modeling were integrated to investigate the differential effects of kerogen types on the hydrocarbon generation potential of lacustrine source rocks. Optimized hydrocarbon generation and expulsion (HGE) models of different kerogen types were established quantitatively upon abundant Rock-Eval/TOC/vitrinite reflectance (Ro) datasets. Three sets of good–excellent source rocks deposited in the fourth (Es4), third (Es3), and first (Es1) members of Paleogene Shahejie Formation, are predominantly types I–II1, II1–II2, and II–III, respectively. The activation energy of types I–II2 kerogen is concentrated (180–230 kcal/mol), whereas that of type III kerogen is widely distributed (150–280 kcal/mol). The original hydrocarbon generation potentials of types I, II1, II2, and III kerogens are 790, 510, 270, and 85 mg/g TOC, respectively. The Ro values of the hydrocarbon generation threshold for type I–III source rocks gradually increase from 0.42% to 0.74%, and Ro values of the hydrocarbon expulsion threshold increase from 0.49% to 0.87%. Types I and II1 source rocks are characterized by earlier hydrocarbon generation, more rapid hydrocarbon expulsion, and narrower hydrocarbon generation windows than types II2 and III source rocks. The kerogen types also affect the HGE history and resource potential. Three types (conventional, tight, and shale oil/gas) and three levels (realistic, expected, and prospective) of hydrocarbon resources of different members in the Liaohe Western Depression are evaluated. Findings suggest that the Es3 member has considerable conventional and unconventional hydrocarbon resources. This study can quantitatively characterize the hydrocarbon generation potential of source rocks with different kerogen types, and facilitate a quick and accurate assessment of hydrocarbon resources, providing strategies for future oil and gas exploration.

Two-timescale autonomous energy management strategy based on multi-agent deep reinforcement learning approach for residential multicarrier energy system

In the residential multicarrier energy system (RMES), autonomous energy management (AEM) is beneficial for prosumers' costs that actively controls generation, energy conversion, and storage in real-time. Conventional model-based AEM methods rely on forecast models of distributed energy resources and proper system parameters, which are difficult for practical application. This article proposes a novel model-free two-timescale real-time AEM strategy for the RMES. The energy management problem in the RMES is time-decomposed into two timescales (hourly-ahead external energy trading and 15-min ahead internal energy conversion), formulated as Markov Games. Then, defining a multi-agent system not only enables separate energy management diagrams but also accelerates learning. Intelligent agents account for optimizing energy trading and energy conversion to minimize daily costs under the training of a deep deterministic policy gradient algorithm. In order to learn a collaborative strategy, all agents are trained centrally while being executed based on local information in a decentralized manner for fast response. A deterministic study indicates that the proposed AEM strategy can effectively and flexibly schedule the operation of components with respect to different price signals and load profiles. In the stochastic study that considers the error thresholds of solar panels generation and loads, the difference between the energy cost of test scenarios with a trained strategy and the no-regret learning method is equal to 0.32%, which is appropriate. In addition, the proposed method not only achieves a reduction in power imbalance but also exhibits lower energy costs when compared to various benchmark methods.

Constraining multi-stage and protracted oil generation of alkaline lacustrine source rocks by heteroatomic compounds

It is unclear whether source rocks deposited in ancient alkaline lakes undergo multiple stages of hydrocarbon generation, particularly of oils. In this study, the lower Permian Fengcheng Formation in the Junggar Basin, China, was investigated using the geochemistry of heteroatomic species, with a focus on N-containing compounds, by negative-ion electrospray high-resolution Fourier transform ion cyclotron resonance mass spectrometry. The maturity parameters based on N-containing compounds (e.g., C0–5/C15–35-DBE 12 N1 and C0–5/C15–35-DBE 15 N1) and aromatic hydrocarbons (TMNr) reveal progressive generation of mature to highly mature crude oils. The polymerization index P1 ([DBE 18 + DBE 15]/DBE 12_N1), alkylation index R1 (RC6−35/RC0−5), and paleo-salinity index (β carotane/nCmax) of the Fengcheng Formation source rocks suggest that the high salinity inhibited molecular polymerization of organic matter and prolonged the oil generation peak, which produced highly mature crude oils in the late stages of hydrocarbon generation. Therefore, alkaline lacustrine source rocks undergo multiple stages of protracted oil generation, which results in a longer oil window and higher threshold for gas generation than in the case of the classic Tissot model. The results highlight the oil generation potential of deep basins containing alkaline lacustrine source rocks and highly mature organic matter, which also have a lower gas-generation potential than previously thought.

The Na<sup>+</sup>/K<sup>+</sup>-ATPase Inhibitor Ouabain Has Different Effects on the Electrophysiological Properties of Excitatory and Inhibitory Neurons in the Entorhinal Cortex E

Na+/K+-ATPase maintains the neuron’s resting potential and the transmembrane gradient of K+ and Na+ cations, thus regulating ion transport and cellular volume. Mutations in Na+/K+-ATPase genes that impair its function can cause significant impairments in the nervous system function, including the development of epilepsy, if not lethal. Different forms of Na+/K+-ATPase are expressed in various classes of neurons and exhibit different characteristics. Thus, the impaired function of Na+/K+-ATPase may differentially affect the functioning of inhibitory and excitatory neurons. This study aims to determine the effects of the Na+/K+-ATPase antagonist ouabain on the electrophysiological characteristics of pyramidal cells and fast-spiking interneurons, as well as its impact on synaptic transmission. The results indicate that exposure to 5 µM ouabain results in depolarization of the resting membrane potential by 5 mV, as well as decreased amplitude and increased duration of the action potential of pyramidal neurons. Furthermore, ouabain caused a decrease in the amplitude of afterhyperpolarization in fast-spiking i-nterneurons. Moreover, both types of neurons exhibited a decrease in the threshold of action potential generation and the current at which depolarization block occurs. The addition of ouabain did not alter other electrophysiological characteristics of neurons. Furthermore, ouabain rapidly attenuates GABAergic transmission without affecting e-xcitatory synaptic transmission. These new findings on the effects of ouabain on excitatory pyramidal neurons and inhibitory interneurons contribute to the understanding of the mechanism underlying changes in the balance of excitation and inhibition in neural networks under Na+/K+-ATPase function impairment.