Excitation Process Research Articles

Exploring the dynamics of H atom guested endofullerene embedded in plasma with ultrashort chirped laser pulses

In this work, the effects of an ultrashort laser pulse on the excitation and ionization dynamics of a hydrogen guested endofullerene system embedded in a quantum plasma environment under spherical encompassment are investigated. The interaction of the plasma environment is considered within the more general exponential cosine screened Coulomb (MGECSC) potential model, and the excitation and ionization dynamics are analyzed through plasma screening parameters. For endohedral confinement, the relevant model that aligns with experimental data and is most suitable for static endohedral encapsulation is the Woods–Saxon potential model. By considering different numerical ranges of the parameters in this model, the effects of various forms of fullerenes are thoroughly explained through the analysis of confinement depth, spherical shell thickness, inner radius and the smoothing parameters. The effects of the characteristic properties of the laser pulse, such as its intensity and frequency, on the probability dynamics are also discussed. All parameters and their respective ranges are important for optimizing system performance. Additionally, the alternatives of all parameters related to the plasma-embedded endofullerene system for probability dynamics are considered. In this context, the findings cause new ideas in the controlled excitation and ionization processes of endofullerene systems embedded in a quantum plasma environment and provide a significant foundation for future experimental studies.

Photoacoustic and plasmaelastic waves propagation in semiconductor medium heated by pulsed excitation with magnetic field effect

Semiconductor materials play a crucial role in the fields of science, engineering, and technology due to their high importance. In this work, photoelastic (PE) deformations due to the photonically excited processes are studied according to the photogenerated carriers (plasma waves) during the recombination processes. A photoacoustic theoretical model for the optically excited Silicon (Si) polymer material under the effect of magnetic field is introduced. The coupled between the acoustic and plasm-thermomechanical waves is considered. The governing equation according to the photo-thermoelasticity theory with acoustic pressure is derived. The optoelectronic and thermoelastic properties of semiconductor material are taken into account. The analytical expression of the main physical fields (temperature, mechanical stress, displacement, carrier density, and acoustic pressure) is obtained mathematically using the harmonic wave technique. The theoretical results are represented graphically due to the strength of the magnetic field in two and three dimensions (2D and 3D) and some comparisons are investigated.

L-Cysteine-Modified Carbon Dots Derived from Hibiscus rosa-sinensis for Thiram Pesticides Identification on Edible Perilla Leaves.

In this work, environmentally friendly fluorescent carbon dots (C-dots) were developed for the purpose of thiram identification in the leaves of perilla plants. Powdered plant petals from Hibiscus rosa-sinensis were hydrothermally combined to create C-dots. Analytical techniques, such as scanning electron microscopy, energy dispersive X-ray spectroscopy, high resolution transmission electron microscopy, Raman spectroscopy, ultraviolet spectroscopy, Fourier transmission infrared spectroscopy, and photoluminescence were employed to examine the properties of C-dots. To enhance their functionality, an l-cysteine dopant was added to the C-dots. Since this process produces highly soluble C-dots in water, it is simple, inexpensive, and safe. The excitation process and the size of the blue luminescent C-dots both affect their photoluminescent activity. Furthermore, thiram in aqueous solutions was effectively identified by using the generated C-dots. Additionally, the ImageJ program was used to measure the colors red, green, and blue. High-resolution TEM (HR-TEM) revealed that the l-cysteine-doped carbon dots had an average particle size of 2.208 nm. Additionally, the lattice fringes observed in the HRTEM image showed a d-spacing of around 0.285 nm, which nearly corresponds to the (100) lattice plane of graphitic carbon. A Raman spectrum study was also performed to investigate the relationship between carbon dots and pesticides in the actual samples. In the end, thiram levels in perilla leaves with nondoped and doped C-dots could be distinguished with 100% accuracy using the constructed partial least-squares discriminant analysis machine learning model. The information gathered therefore demonstrated that the synthetic C-dots successfully and efficiently provide rapid and sensitive detection of hazardous pesticides in edible plant products.

Reduced Scaling Correlated Natural Transition Orbitals for Multilevel Coupled Cluster Calculations.

Multilevel coupled cluster theory offers reduced scaling computation of intensive properties in systems that are too large for standard coupled cluster calculations. A significant benefit of the multilevel coupled cluster framework is the possibility of calculating intensive properties that are not tightly localized if an appropriate set of active orbitals is used. Correlated natural transition orbitals (CNTOs) are tailored to describe excitation processes. For multilevel coupled cluster singles and doubles (MLCCSD) and singles and perturbative doubles (MLCC2) calculations, the construction of CNTOs generally becomes the computational bottleneck. Here, we demonstrate how CNTOs can be obtained with operations, eliminating the -scaling steps involved in the original approach. This reduction in scaling moves the bottleneck of MLCC2 and MLCCSD calculations from the active orbital space preparation to the MLCC2 and MLCCSD equations with -scaling.

FLT3 signaling inhibition abrogates opioid tolerance and hyperalgesia while preserving analgesia

Navigating the duality of opioids’ potent analgesia and side effects, including tolerance and hyperalgesia, is a significant challenge in chronic pain management, often prompting hazardous dose escalation to maintain analgesic effects. The peripheral mu-opioid receptor (MOR) is known to mediate these contradictory effects. Here, we show that the fms-like tyrosine kinase receptor 3 (FLT3) in peripheral somatosensory neurons drives morphine tolerance and hyperalgesia in a male rodent model. We found that chronic morphine treatment increases FLT3 and MOR co-expression, and that inhibiting FLT3 represses MOR-induced hyperactivation of the cyclic adenosine monophosphate (cAMP) signaling pathway, mitigating maladaptive excitatory processes engaged after chronic morphine treatment. Furthermore, in postsurgical or inflammatory models of chronic pain, co-administering morphine with a FLT3-specific inhibitor not only prevents or suppresses tolerance and hyperalgesia but also potentiates the analgesic efficacy of morphine, without aggravating other morphine-induced adverse effects. Our findings suggest that pairing morphine with FLT3 inhibitors could become a promising avenue for chronic pain management to safely harness the power of opioids, without the risk of dose escalation. By enhancing morphine analgesic potency through FLT3 inhibition, this approach could minimize opioid dosage, thereby curtailing the risk of addiction and other opioid-related side effects.

Ultrafast Spectroscopic Studies on Excited State Dynamics of Different Alkyl Substituted Perylene Monoimides in Solution and Thin Films

AbstractPerylene monoimides (PMI) are a unique class of polyaromatic molecules, which are known to undergo interesting excited state processes, making them attractive for the applications in optoelectronic devices. In this paper a comprehensive investigation is conducted on the photophysical properties and excited state dynamics of a series of PMI derivatives (PMI‐C18, PMI‐CE6, PMI‐C8, and PMI‐C6), with varying side chains substituted at the imide position. These studies involved utilization of both steady state and time resolved spectroscopic techniques. Femtosecond transient absorption (TA) spectroscopic studies demonstrated that PMI derivatives exhibit similar fluorescence characteristic in solution, irrespective of the various side chains substituted at the imide position. However, in thin films the various side chains led to prominent differences in their packing arrangement, which leads to difference in the TA spectra as compared to solution. The difference in the packing arrangement in PMI thin films is studied using X‐ray diffraction (XRD) spectroscopy. It is notable that the PMI‐CE6 thin films exhibited the existence of triplet state. The distinctive behavior of PMI‐CE6 is attributed to the distinct packing arrangement, providing role of molecular structure in influencing the excited state dynamics. The triplet state formation in PMI thin films renders them well‐suited for utilization in optoelectronic devices.

Study on the aerodynamic characteristics of reentry capsule with obtuse head inverted cone under hypersonic chemical nonequilibrium flow

Abstract During spacecraft reentry, the aerodynamic characteristics of the reentry capsule with a sizeable obtuse head inverted cone (OBHIC) in a hypersonic state are the key factors in the design of controlled reentry trajectory, the design of trim angle of attack (AoA), and the accuracy of fall point of capsules. This paper establishes a numerical simulation algorithm of a hypersonic chemical nonequilibrium flow field by considering high-temperature real gas effects. The reentry capsule’s aerodynamic and flow field characteristics are predicted and analyzed. The component transport equations for chemical reactions are added to the Navier-Stokes equations, enabling precise modeling of gas molecule vibrational excitation and ionization processes. A half-model multi-block structured mesh is employed to construct the aerodynamic profile of the reentry capsule with OBHIC. The aerodynamic characteristics and pressure distribution of the reentry capsule were calculated and analyzed under the typical conditions of flight altitude of 40~80 km, flight velocity of 6~27 Ma, and AoA of 15°~24°. The results of the aerodynamic characteristics prediction show that the aerodynamic characteristics of the reentry capsule are little affected by the incoming flow velocity in a hypersonic state but significantly affected by the AoA. As the AoA increases, the lift coefficient CL increases linearly, the drag coefficient CD decreases linearly, the lift-to-drag ratio K rises linearly, and K increases from 0.19 to 0.29. In its hypersonic state, the reentry capsule exhibits a low lift-to-drag ratio, characterized by high drag and low lift coefficients. The results of this paper play an essential role in the reentry flight dynamics and reentry trajectory design of the reentry capsule. Moreover, it can further ensure the safety and reliability of the reentry flight of spacecraft.

Hybrid Hamiltonian Simulation for Excitation Dynamics.

Hamiltonian simulation is one of the most anticipated applications of quantum computing. Quantum circuit depth for implementing Hamiltonian simulation is commonly time dependent using Trotter-Suzuki product formulas so that long time quantum dynamic simulations (QDSs) become impratical for near-term quantum processors. Hamiltonian simulation based on Cartan decomposition (CD) provides an appealing scheme for QDSs with fixed-depth circuits, while it is limited to a time-independent Hamiltonian. In this work, we generalize this CD-based Hamiltonian simulation algorithm for studying time-dependent systems by combining it with variational quantum algorithms. The time-dependent and time-independent parts of the Hamiltonian are treated by using variational and CD-based Hamiltonian simulation algorithms, respectively. As such, this hybrid Hamiltonian simulation requires only fixed-depth quantum circuits to handle time-dependent cases while maintaining a high accuracy. We apply this new algorithm to study the response of spin and molecular systems to δ-kick electric fields and obtain accurate spectra for these excitation processes.

Coordination of Pharyngeal and Esophageal Phases of Swallowing.

Although swallowing has been reviewed extensively, the coordination of the phases of swallowing have not. The phases are controlled by the brainstem, but peripheral factors help coordinate the phases. The occurrence, magnitude, and duration of esophageal phase depends upon peripheral feedback activated by the bolus. The esophageal phase does not occur without peripheral feedback from the esophagus. This feedback is mediated by esophageal slowly-adapting mucosal tension receptors through the recurrent and superior laryngeal nerves. A similar reflex mediated by the same peripheral pathway is the activation of swallowing by stimulation of the cervical esophagus. This reflex occurs primarily in human infants and animals, and this reflex may be important for protecting against aspiration after esophago-pharyngeal reflux. Not only are there inter-phase excitatory processes, but also inhibitory processes. A significant inhibitory process is deglutitive inhibition. When one swallows faster than peristalsis ends, peristalsis is inhibited by the new pharyngeal phase. This process prevents the ongoing esophageal peristaltic wave from blocking the bolus being pushed into the esophagus by the new wave. The esophageal phase returns during the last swallow of the sequence. This process is probably mediated by mucosal tension receptors through the superior laryngeal nerves. A similar reflex exists, the pharyngo-esophageal inhibitory reflex, but studies indicate that it is controlled by a different neural pathway. The pharyngo-esophageal inhibitory reflex is mediated by mucosal tension receptors through the glossopharyngeal nerve. In summary, there are significant peripheral processes that contribute to swallowing, whereby one phase of swallowing significantly affects the other.

Photophysics of Nitro-Substituted Unnatural Nucleic Acid Base.

The unnatural nucleic acid base (uNAB), 6-amino-3-methyl-5-nitropyridin-2(1H)one, often referred to as Z can form a base pair with the uNAB 2-aminoimidazo[1,2-a]-1,3,5-triazin-4(8H)-one (referred to as P) and is analogous to a guanine-cytosine (G-C) pair. However, it is well-known that the nonradiative decay pathway of the P-Z pair is significantly different from that of the G-C pair (Cui et al., Front. Chem. 2020, 8, 605117-605125). In this work, we study the excited state processes in Z using state-of-the-art multireference methods and dynamical techniques to ascertain the predominant nonradiative channels. We find that unlike in the natural NABs, the excited state processes in Z are driven primarily by the -NO2 group rotation. The electron-withdrawing effect of the -NO2 substituent plays a crucial role. We further ascertained that ultrafast deactivation channels are possible in Z and identified the stationary point geometries that are responsible for these channels.

Application of Graphene in Acoustoelectronics.

An interdigital transducer structure was fabricated from multilayer graphene on the surface of the YZ-cut of a LiNbO3 ferroelectric crystal. The multilayer graphene was prepared by CVD method and transferred onto the surface of the LiNbO3 substrate. The properties of the multilayer graphene film were studied by Raman spectroscopy. A multilayer graphene (MLG) interdigital transducer (IDT) structure for surface acoustic wave (SAW) excitation with a wavelength of Λ=60 μm was fabricated on the surface of the LiNbO3 crystal using electron beam lithography (EBL) and plasma chemical etching. The amplitude-frequency response of the SAW delay time line was measured. The process of SAW excitation by graphene IDT was visualized by scanning electron microscopy. It was demonstrated that the increase in the SAW velocity using graphene was related to the minimization of the IDT mass.

ELECTRON SOURCE BASED ON EMERGENCE OF SELF-INJECTED ELECTRON BUNCH AT PLASMA WAKEFIELD EXCITATION BY A TW LASER PULSE

Wakefield acceleration methods are known due to some their advantages. The main of them is the high accelerating gradient up to several teravolts per meter. In the paper another important advantage is concluded to the possibility of using a wakefield accelerator as a source of electrons by means of obtaining self-injected bunches and their acceleration. The result is the simulation of the process of plasma wakefield excitation by a laser pulse with an energy of tens of mJ and a power of 1…2 TW for obtaining the promising electron source. Homogeneous and Gaussian plasma profiles were investigated and compared to increase the energy of the self-injected bunches. The laser parameters were taken that corresponded to the parameters of the laser setup in the Institute of Plasma Electronics and New Methods of Acceleration of the National Scientific Center “Kharkiv Institute of Physics and Technology”. Based on the results of the simulation, the possibility of obtaining relativistic self-injected bunches that can be used for further laser acceleration experiments, including dielectric laser acceleration, was demonstrated.

Disturbances of the process of synaptic elimination and its reflection in the wave N170 of auditory evoked potential (AEP) in first psychotic episode of paranoid schizophrenia

The reaction of cortical structures of different significance (associated with delusions and hallucination and neutral ones) was studied. The work was conducted in patients with paranoid schizophrenia and normal control (24 patients with paranoid schizophrenia, 15 controls). In patients in frontal areas paradox effect (PE) in AEPs with the increase of both parameters of N170 component was revealed. In central and temporal areas PEs were found in N170 component with the decrease of both parameters of this component. These results point to the “conflict” between the processes of excitation and inhibition in schizophrenia. In schizophrenia patients Pes were revealed in auditory and visual modalities (EVPs and VEPs) on the N170 wave with the unidirectional shifts (increase and decrease) of both parameters in the same cortical areas in AEPs and VEPs. It is supposed that ERP disturbances revealed in patients with schizophrenia are due to the pathology of the synaptic pruning causing the imbalance of excitation-inhibition and leading to the psychosis onset.

Anomalous Directed Percolation on a Dynamic Network Using Rydberg Facilitation.

The facilitation of Rydberg excitations in a gas of atoms provides an ideal model system to study epidemic evolution on (dynamic) networks and self-organization of complex systems to the critical point of a nonequilibrium phase transition. Using MonteCarlo simulations and a machine learning algorithm we show that the universality class of this phase transition can be tuned but is robust against decay inherent to the self-organization process. The classes include directed percolation (DP), the most common class in short-range spreading models, and mean-field (MF) behavior, but also different types of anomalous directed percolation (ADP), characterized by rare long-range excitation processes. In a frozen gas, ground state atoms that can facilitate each other form a static network, for which we predict DP universality. With atomic motion the network becomes dynamic by long-range (Lévy-flight type) excitations. This leads to continuously varying critical exponents, varying smoothly between DP and MF values, corresponding to the ADP universality class. These findings also explain the recently observed critical exponent of Rydberg facilitation in an ultracold gas experiment [Helmrich etal., Nature (London) 577, 481 (2020)NATUAS0028-083610.1038/s41586-019-1908-6], which was in between DP and MF values.

Fluorescence scattering under the Stokes–Mueller formalism determines the orientational distribution of fluorophores and the nature of optically active biological proteins

Abstract In the current paper, we represent intrinsic fluorescence anisotropies as four-dimensional normalized Stokes vectors defined by the maximum excitation and emission in the fluorescence process with respect to linear, linear-45 and circular polarizations of light. Depending upon the transition moments for absorption/excitation and emission of fluorophores, eight types of these Stokes vectors can be realized from the Mueller fluorescence matrix of the system. These Stokes vectors probe the orientational distribution of fluorophores and predict the nature of optically active biological proteins, whether laevorotatory or dextrorotatory. The orthogonality relation between the Stokes vectors corresponding to the excitation and emission processes of fluorescence connects the molecular ground and excited states of biological and non-biological systems.

Study of the electronic structure and electron impact excitation cross section of helium impurities in spherical quantum dots

This manuscript is devoted to explore the atomic structure and electron impact excitation process of atom impurities in quantum dots. To achieve this goal, a method that solves the fully relativistic Dirac equation within the framework of relativistic configuration interaction is proposed. The Gaussian potential is used, which can accurately describe the location of impurities in quantum dots and their local effects on the surrounding electron cloud. The coupled Dirac equation is modified to include a new central potential, providing solutions that include both the continuous and bound state wave functions. The process of electron impact excitation is elucidated using the distorted wave method, all within the framework of relativistic Dirac theory. For illustrative purposes, a detailed investigation of the excitation energies, transition rates, wave functions, and excitation cross sections is carried out for a wide range of confinement strengths of the potential and quantum dot radii, using the helium impurities in spherical quantum dots as an example. Our results reveal that for a given confinement strength of the potential, the bound state wave functions are initially pulled into the inner region by the attractive Gaussian potential well, but eventually reflect the free atom scenario at large quantum dot radii. In contrast, the continuous electron wave functions exhibit monotonic variations as a function of the quantum dot radii. Such behavior of the wave functions gives rise to distinctive phenomena in the variation of excitation energies, transition rates, and excitation cross sections in relation to the potential parameters. Good agreement between the present results and existing data, where available, is obtained. This work holds importance not only for basic research in atomic physics but also for the optical and electronic applications of quantum dots. I.e., in the design and optimization of quantum dot lasers and quantum dot sensors.

Magic-Angle Exciton Coupling in a Molecular Solid: Optical Consequence of Null-Coulombic Coupling.

Instances of magic angle excitonic coupling and its optical consequences are infrequently documented in the literature, yet they hold fundamental significance in understanding excited state electronic processes within molecular aggregates. Weak/null long-range dipolar Coulombic coupling is the characteristic of chromophore arrays positioned in a magic angle configuration. This study presents a rare example of such phenomena in CF3DPT solids, resulting in a high fluorescence quantum efficiency of 62 ± 3% in the aggregated solid state. Supported by computational calculations, we validate our experimental findings of null-Coulombic coupling and significant charge transfer (CT) coupling within the solid state.

Особливості вікових змін організації мозкової діяльності військовослужбовців, які визначають функціональну рухливість нервових процесів

One of the individual-typological qualities of a person characterizing the processes of inhibition and excitation in the central nervous system is the level of functional motility of nervous processes (FMNP). The degree of its development largely determines individual differences in adaptive capabilities, the speed of orientation in new conditions, and the ability to adapt one’s behavior to changing environmental factors. Therefore, this characteristic is crucial for professional selection and monitoring of professional efficiency. Our work aimed to determine the level of FMNP in three age groups of representatives of different military specialties and to study the peculiarities of the functioning of neural networks in the brain that are formed during the FMNP test. During the original computer tests to assess FMNP, electroencephalograms (EEG) were recorded with subsequent coherent analysis. Group 1 (18-23 years old) had the lowest level of FMNP and differed significantly from group 3 (35-54 years old). A coherent analysis of EEG showed that the neurophysiological basis for a higher level of FMNP during passing tests for its determining by the participants of the group 3 could be a higher level of motivation and selective attention to visual stimuli due to δ-band coherence in the fronto-parietal regions, better synchronization of the distant neural clusters due to the developed neural network in the θ-band (in the parietal, fronto-parietal and temporal-central areas), higher level of the occipital-central (i.e. visual-motor) integration and blocking of distracting information due to more connections in α-band range. Since most differences were found in the α-band, it could be assumed that the α-activity is of crucial importance for the successful passing of the FMNP test by the older age group. Key words: functional motility of nervous processes; coherence; neural networks; electroencephalogram; age-related changes.

Research on Pipeline Stress Detection Method Based on Double Magnetic Coupling Technology.

Oil and gas pipelines are subject to soil corrosion and medium pressure factors, resulting in stress concentration and pipe rupture and explosion. Non-destructive testing technology can identify the stress concentration and defect corrosion area of the pipeline to ensure the safety of pipeline transportation. In view of the problem that the traditional pipeline inspection cannot identify the stress signal at the defect, this paper proposes a detection method using strong and weak magnetic coupling technology. Based on the traditional J-A (Jiles-Atherton) model, the pinning coefficient is optimized and the stress demagnetization factor is added to establish the defect of the ferromagnetic material. The force-magnetic relationship optimization model is used to calculate the best detection magnetic field strength. The force-magnetic coupling simulation of Q235 steel material is carried out by ANSYS 2019 R1 software based on the improved J-A force-magnetic model. The results show that the effect of the stress on the pipe on the magnetic induction increases first and then decreases with the increase in the excitation magnetic field strength, and the magnetic signal has the maximum proportion of the stress signal during the excitation process; the magnetic induction at the pipe defect increases linearly with the increase in the stress trend. Through the strong and weak magnetic scanning detection of cracked pipeline materials, the correctness of the theoretical analysis and the validity of the engineering application of the strong and weak magnetic detection method are verified.

Interference patterns of two-photon excited fluorescence by spatial beam shaping

We report on two-photon excited fluorescence interference patterns produced by spatial laser beam shaping. Thereto, a focused spatially modulated laser beam component is overlapped with an unfocused Gaussian beam component, and both are directed on a cuvette filled with dye. The phase retardance between the two common path laser components is precisely adjusted by a 2D liquid crystal modulator. With this method it is possible to generate various fluorescence patterns which exhibit sharp features and a high contrast due to constructive and destructive interference of a two-photon excitation process. The developed spatial shaping interference technique with two-photon excitations has a high potential for optical and biophotonic imaging applications.