We study laser-assisted fast (
e
, 2
e
) collisions on atomic hydrogen both in perturbative and in nonperturbative regimes of laser radiation. We calculate multiphoton triple differential cross ...sections in asymmetric coplanar kinematics employing the first Born approximation in the projectile–target interaction. The study allows us to test the robustness of our recently formulated quasi-Sturmian-Floquet method to treat the dressing of the initial and final atomic states by the laser field. In both radiation regimes our method exhibits high efficiency for different net numbers of photons exchanged between the colliding system and the laser field.
Graphical abstract
In this review, we describe dielectric properties of biological tissues and liquids in the context of terahertz (THz) biophotonics. We discuss a model of the THz dielectric permittivity of water and ...water-containing media, which yields analysis of the relaxation and damped resonant molecules modes. We briefly describe modern techniques of THz spectroscopy and imaging employed in biophotonics with a strong emphasize on a THz time-domain spectroscopy. Furthermore, we consider the methods of sub-wavelength resolution THz imaging and the problem of THz wave delivery to hard to access tissues and internal organs. We consider the THz dielectric properties of biological solutions and liquids. Although strong absorption by water molecules prevents THz-waves from penetration of hydrated tissues and probing biological molecules in aqueous solutions, we discuss approaches for overcoming these drawbacks – novel techniques of freezing and temporal dehydration by application of hyperosmotic agents which have a potential for cancer detection. We review recent applications of THz technology in diagnosis of malignancies and aiding histology paying particular attention to the origin of contrast observed between healthy and pathological tissues. We consider recent applications of THz reflectometry in sensing the thinning dynamics of human pre-corneal tear film. Modern modalities of THz imaging, which relies on the concepts of multi-spectral and multi-temporal domains and employing the principles of color vision, phase analysis and tomography are discussed. Novel methods of THz spectra analysis based on machine learning, pattern recognition, chemical imaging and the revealing of the spatial distribution of various substances in a tissue, are analyzed. Advanced thermal model describing biological object irradiated by THz waves and phantoms mimicking the optical properties of tissues at THz frequencies are presented. Finally, application of the high-resolution THz spectroscopy in analytic chemistry, biology and medicine are described.
The clinical use of optical methods for
skin imaging is limited by skin strong scattering properties, which reduce image contrast and probing depth. The efficiency of optical methods can be improved ...by optical clearing (OC). However, for the use of OC agents (OCAs) in a clinical setting, compliance with acceptable non-toxic concentrations is required.
OC of
human skin, combined with physical and chemical methods to enhance skin permeability to OCAs, was performed to determine the clearing-effectiveness of biocompatible OCAs using line-field confocal optical coherence tomography (LC-OCT) imaging.
Nine types of OCAs mixtures were used in association with dermabrasion and sonophoresis for OC protocol on three volunteers hand skin. From 3D images obtained every 5 min for 40 min, the intensity and contrast parameters were extracted to assess their changes during the clearing process and evaluate each OCAs mixture's clearing efficacy.
The LC-OCT images average intensity and contrast increased over the entire skin depth with all OCAs. The best image contrast and intensity improvement was observed using the polyethylene glycol, oleic acid, and propylene glycol mixture.
Complex OCAs featuring reduced component concentrations that meet drug regulation-established biocompatibility requirements were developed and proved to induce significant skin tissues clearing. By allowing deeper observations and higher contrast, such OCAs in combination with physical and chemical permeation enhancers may improve LC-OCT diagnostic efficacy.
A square integrable parabolic Sturmian functions approach is suggested to calculate fully differential cross sections for the hydrogen ionization by impact of fast antiprotons. The problem is recast ...as an inhomogeneous Schrödinger equation for the Coulomb three-body system
(
e
-
,
p
+
,
p
-
)
. The transition amplitude is expressed as an expansion in terms of ’basis amplitudes’ that contain the angular dependence. They are provided here in closed form thereby avoiding numerical integration of very rapidly oscillating functions. The angular dependence is weighted by expansion coefficients whose evaluation is the computationally demanding part. These coefficients are expressed in terms of overlaps between the basis Sturmian functions and the result of the action of the incident channel potential action onto the initial state. Convergence with respect to the basis size is achieved numerically. Our approach makes the high enough incident energy assumption that the Born series for the Coulomb three-body Green’s function converges pretty fast, leaving the antiproton-electron interaction to be treated as a perturbation. The performed numerical calculations validate this assumption at 500 keV incident energy, and provide cross sections for a momentum transfer of 0.25 a.u. in agreement with three other theoretical results.
Introduction
The study of voluntary attention is necessary to assess the effectiveness of therapeutic, psychotherapeutic and psychocorrective measures. Evaluation of the effectiveness of treatment by ...analyzing the dynamics of indicators of voluntary attention of adolescents with endogenous mental pathology is necessary for the development of personalized patient management
Objectives
To analyze the dynamics of indicators of voluntary attention to memory in adolescents with endogenous mental pathology during treatment.
Methods
clinical-catamnestic, pathopsychological methods. We examined 153 patients aged 12-16 years (average-13.7 years) with diagnoses of F21.3, F21.4, F20.8xx3 (ICD-10). The comparison group consisted of 143 healthy peers. Methods children’s color train test, Schulte tables. All subjects were examined twice – at the beginning of therapy and at discharge from the clinic.
Results
Analysis of the results of comparing the dynamics of attention in adolescents with endogenous mental diseases during the initial examination and during repeated examination showed that adolescents with diagnoses of F21.3, F21.4, as well as with a diagnosis of F20.8xx3 improve their attention indicators during repeated examination (at p< 0.01). Adolescents of the experimental group showed better results compared to the control group, which indicates that there is a positive therapeutic dynamics of attention in sick adolescents. Comparison of therapeutic dynamics of attention of adolescents with endogenous mental diseases depending on the diagnosis revealed significant differences. Adolescents from the F21 group performed better than the F20 group (at P< 0.01).
Conclusions
The Study showed the effectiveness of the choice of this methodological tool in assessing the therapeutic dynamics of patients.
The experiment Neutrino-4 started in 2014 with a detector model and continued with a full-scale detector in 2016–2021. In this article, we describe all the steps of the preparatory work on this ...experiment. We present all results of the Neutrino-4 experiment with increased statistical accuracy provided to date. The experimental setup is constructed to measure the flux and spectrum of the reactor antineutrinos as a function of distance to the center of the active zone of the SM-3 reactor (Dimitrovgrad, Russia) in the range of 6–12 meters. Using all the collected data, we performed a model-independent analysis to determine the oscillation parameters Δm214 and sin22θ14. The method of coherent summation of measurement results allows us to directly demonstrate the oscillation effect. We present the analysis of possible systematic errors and the MC model of the experiment, which considers the possibility of the effect manifestation at the present precision level. As a result of the analysis, we can conclude that at currently available statistical accuracy, we observe the oscillations at the 2.9 σ level with the parameters Δm214 = (7.3 ± 0.13st ± 1.16syst) eV2 = (7.3 ± 1.17) eV2 and sin22θ = 0.36 ± 0.12 stat(2.9σ). Monte Carlo based statistical analysis gave an estimation of the confidence level at 2.7σ. We plan to improve the currently working experimental setup and create a completely new setup in order to increase the accuracy of the experiment by 3 times. We also provide a brief analysis of the general experimental situation in the search for sterile neutrinos.
The parabolic quasi-Sturmian approach, recently introduced for the calculation of ion–atom ionizing collisions, is adapted and applied here to the single ionization of helium induced by an ...intermediate-energy proton impact. Within the method, the ionization amplitude is represented as the sum of the products of the basis amplitudes associated with the asymptotic behavior of the continuum states of the two noninteracting hydrogenic subsystems (e−,He+) and (p+,He+). The p−e interaction is treated as a perturbation in the Lippmann–Schwinger-type (LS) equation for the three-body system (e−,He+,p+). This LS equation is solved numerically using separable expansions for the proton–electron potential. We examine the convergence behavior of the transition amplitude expansion as the number of terms in the representation of the p−e interaction is increased and find that, for some kinematic regimes, the convergence is poor. This difficulty, which is absent for a higher proton energy impact, is solved by varying the momentum of the auxiliary proton plane wave introduced into the basis function. Fully differential cross-sections are calculated and compared with experimental data for 75 keV protons and the results obtained with the 3C model.
In this paper, we report on an approach for shaping the spectra of THz pulse generation in photoconductive antennas (PCAs) by frequency-dependent impedance modulation. We introduce a theoretical ...model describing the THz pulse generation in PCAs, and accounting for impedances of the photoconductor and of the antenna. Additionally we account a detector response for comparative analysis with experimental data. In order to showcase an impact of frequency-dependent impedance modulation on the spectra of THz pulse generation, we applied this model to simulating broadband PCAs with log-spiral topology. Finally, we fabricated two different log-spiral PCAs and characterized them experimentally using the THz pulsed spectroscopy. The observed results demonstrate agreement between the theoretical model and experiment, justifying the potential of shaping the spectra of THz pulse generation in PCAs by modulation of frequency-dependent impedances. This approach makes it possible to optimize PCA performance and thus accommodes the needs of THz pulsed spectroscopy and imaging in fundamental and applied branches of THz science and technology.
Over the past few decades, significant attention has been paid to the biomedical applications of terahertz (THz) technology. Nowadays, THz spectroscopy and imaging have allowed numerous demanding ...problems in the biological, medical, food, plant and pharmaceutical sciences to be solved. Among the biomedical applications, the label-free diagnosis of malignant and benign neoplasms represents one of the most attractive branches of THz technology. Despite this attractiveness, THz diagnosis methods are still far from being ready for use in medical practice. In this review, we consider modern research results in the THz diagnosis of malignant and benign neoplasms, along with the topical research and engineering problems which restrain the translation of THz technology to clinics. We start by analyzing the common models of THz-wave-tissue interactions and the effects of tissue exposure to THz waves. Then, we discuss the existing modalities of THz spectroscopic and imaging systems, which have either already been applied in medical imaging, or hold strong potential. We summarize the earlier-reported and original results of the THz measurements of neoplasms with different nosology and localization. We pay attention to the origin of contrast between healthy and pathological tissues in the THz spectra and images, and discuss the prospects of THz technology in non-invasive, minimally invasive and intraoperative diagnosis, as well as in aiding histology. Finally, we review the challenging problems of THz diagnosis, as well as attempts to solve them, which should bring THz technology much closer to medical practice. This review allows one to objectively uncover the benefits and weaknesses of THz technology in the diagnosis of malignant and benign neoplasms.
We applied terahertz (THz)-pulsed spectroscopy to study ex vivo the refractive index and absorption coefficient of human brain gliomas featuring different grades, as well as perifocal regions ...containing both intact and edematous tissues. Glioma samples from 26 patients were considered and analyzed according to further histological examination. In order to fix tissues for the THz measurements, we applied gelatin embedding, which allows for sustaining their THz response unaltered, as compared to that of the freshly excised tissues. We observed a statistical difference between the THz optical constants of intact tissues and gliomas of grades I to IV, while the response of edema was similar to that of tumor. The results of this paper justify a potential of THz technology in the intraoperative label-free diagnosis of human brain gliomas for ensuring the gross-total resection.
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