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We examine the validity of Eq. Sabatyan and M. We show that Eq. In particular, we show that, to agree with the implicit criterion for representing traveling waves, given when using the Fresnel—Kirchoff integral [Eq. The results obtained correcting Eq. We demonstrate the importance of adequately taking into account the criterion implicitly assumed in the Fresnel—Kirchoff integral to represent traveling waves.
A methodology based on convolutional neural network CNN is proposed for joint classification of transmitting user number and modulation format in a multiuser free-space optical communication FSOC link. The proposed methodology relies on amplitude information of received mixed signal. In-phase and quadrature components of users that are sharing time and bandwidth resources transmitting into the same optical wireless access point and interfering within each other are analyzed. The proposed approach utilizes the constellation diagrams of the received mixed symbols to generate image data sets that are fed into CNN input. The designed CNN model with three convolutional layers was tested for: varying image resolutions, image-data set size, varying number of received symbols, and atmospheric turbulence to identify optimal parameters and processing time for system design and implementation.
Moreover, the CNN demonstrated robustness against atmospheric turbulence and suggested immunity to additive noise. Therefore, the proposed methodology proved to be a promising and feasible solution for practical implementation of an intelligent optical wireless receiver for aerial and terrestrial FSOC links. Fiber Bragg grating has embraced the area of fiber optics since the early days of its discovery, and most fiber optic sensor systems today make use of fiber Bragg grating technology. Researchers have gained enormous attention in the field of fiber Bragg grating FBG -based sensing due to its inherent advantages, such as small size, fast response, distributed sensing, and immunity to the electromagnetic field. Fiber Bragg grating technology is popularly used in measurements of various physical parameters, such as pressure, temperature, and strain for civil engineering, industrial engineering, military, maritime, and aerospace applications.
Nowadays, strong emphasis is given to structure health monitoring of various engineering and civil structures, which can be easily achieved with FBG-based sensors. Depending on the type of grating, FBG can be uniform, long, chirped, tilted or phase shifted having periodic perturbation of refractive index inside core of the optical fiber. Basic fundamentals of FBG and recent progress of fiber Bragg grating-based sensors used in various applications for temperature, pressure, liquid level, strain, and refractive index sensing have been reviewed.
A major problem of temperature cross sensitivity that occurs in FBG-based sensing requires temperature compensation technique that has also been discussed in this paper. Functional brain network analysis is important for understanding the causes of neurological disorders and relevant brain mechanisms. Lately, functional near-infrared spectroscopy fNIRS yields outputs similar to the blood-oxygen-level-dependent signals of functional magnetic resonance imaging fMRI , and numerous studies have been conducted on functional connectivity and causality using fMRI and fNIRS.
Despite the existence of numerous analysis toolboxes for fNIRS, most of them are difficult to use because they involve numerous steps, coefficients, and related files. Given that OptoNet consists of a simple and intuitive graphical user interface, users can readily analyze the cortical networks of the brain for fNIRS signals. To evaluate the efficacy of the developed toolbox, the finger tapping task experiment—extensively used in brain functional activities and causal connectivity studies—was employed. The experiment was performed using the right and left hands, and both hands simultaneously, and the consequently elicited brain cortical network activity was analyzed using developed OptoNet. We developed an optical cryostat with a sample-rotation unit for polarization-sensitive measurement in terahertz THz and infrared IR ranges.
Importantly, this control is realized in-situ , i. These measurements revealed strong angular dependence of the sample transmission. The developed cryostat is capable for solving numerous demanding problems of THz and IR spectroscopy in condensed matter physics and materials science, biophysics, chemical, and pharmaceutical sciences. Infrared thermography can be used as a measuring technology that records the thermal reaction of body to an external effect.
In this case, the external impact is low-intensity optical radiation LOR. Temperature is measured using a short-wave 1. It is known that LOR produces a therapeutic effect. At the same time, the reason for this action remains unclear. Temperature measurements continue during and after irradiation for 20 min. To interpret the results, a change in the temperature of the palm of volunteers who drank hot water is also investigated.
It is found that the temperature after exposure to LOR is definitely established at a new level, depending on the radiation dose. Changes in surface temperature are associated with stimulation of blood flow. Literature data suggest that the observed response of the body to radiation may be caused by the work of the vascular relaxation factor, photoreactivation of superoxide dismutase, and the death of blood cells during irradiation.
Terahertz THz solid immersion microscopy is a modality of THz imaging, which allows one to overcome the Abbe diffraction limit and provides high energy efficiency due to the absence of subwavelength apertures and probes in an optical scheme. In our previous study, we introduced an original arrangement of the THz solid immersion lens SIL , which provides superior spatial resolution of 0. Next, we described the continuous-wave THz solid immersion microscope, which relies on the proposed SIL and exploits a backward-wave oscillator and a Golay cell as an emitter and a detector, respectively. Finally, we studied experimentally the spatial resolution of this microscope and visualized several representative objects featuring subwavelength structural inhomogeneities.
The observed results revealed potential of the THz solid immersion microscopy in nondestructive testing and biophotonics. We analyze the pumping of the graphene-based laser heterostructures by infrared radiation using the numerical model. Our calculations are based on the thermodiffusion-drift carrier transport model. We demonstrate that the proposed optical pumping method can provide an efficient injection of the cool electron—hole plasma into the GL and the interband population inversion in the GL. Since the energy gap in b-As layer can be smaller than the energy of optical phonons in the GL, the injected electron—hole plasma can be additionally cooled down to the temperatures lower than the lattice temperature.
This promotes a stronger population inversion that is beneficial for realization of the GL-based optically pumped terahertz and far-infrared laser, plasmon emitters, and the superluminescent downconverters. We also compare the efficiency of optical pumping through the graded-gap and uniform absorbing-cooling layers. Mesenchymal stem cells MSCs represent a significant interest for cell therapy applications and, being primary cells, undergo gradual aging in culture. We studied the effects of low-intensity infrared laser irradiation during aging of MSCs in culture.
Both young and aged MSCs respond to low irradiation doses 0. Aged cells demonstrate a relatively higher growth response to low doses, but they are significantly more susceptible to deleterious effects of middle doses compared to young cells. Studies of MSC aging during long-term culture under hypoxia conditions demonstrate that low-dose irradiation of MSCs every 2 days in culture substantially increases the number of population doublings, compared to the control group. In addition, irradiated cells persisted in culture for two passages 4 days longer than their control counterparts.
However, irradiated cells did not proliferate more rapidly if irradiation was omitted. We conclude that growth responses of young and aged murine MSCs to infrared laser irradiation differ significantly and that regular irradiation affects MSC aging in culture but does not result in a bonafide retardation of aging process. This review highlights recent and novel trends focused on metallic plasmonic and dielectric metasurfaces in photoconductive terahertz THz devices.
We demonstrate the great potential of its applications in the field of THz science and technology, nevertheless indicating some limitations and technological issues. From the state-of-the-art, the metasurfaces are, by far, able to force out previous approaches like photonic crystals and are capable of significantly increasing the performance of contemporary photoconductive devices operating at THz frequencies. The effect of laser-induced heating of the upconversion particles is shown, which introduces distortions in the measured power and temperature dependences of the upconversion luminescence.
We propose a technique for calibrating the temperature dependence of upconversion particle luminescence, which should improve the accuracy of temperature measurements. The technique is based on the stabilization of upconversion particles temperature, which provides the suppression of laser-induced heating of upconversion particles. Application of a fiber Fabry—Perot interferometer for studying the sound response of cellular structures and aqueous solutions is discussed.
The distribution of frequency intensities in the acoustic spectrograms yields evaluation of a biological system response to the external exposure. In a yeast suspension, few minutes after the sound irradiation with the frequency of 3 kHz and the sound pressure of 50 to 60 dB, we observed regular fluctuations in the output acoustic signal, with the maximal period of about s. Furthermore, a sound response in the frequency range of to Hz maintained in signals for few minutes after the exposure. The observed results demonstrate that the proposed interferometric sensor has strong potential in biology and medicine since it is quite simple, portable, and highly sensitive device for analyses the sound response of a living system.
An experimental setup with a laser fiber optic probe has been developed, and the vibration dynamics of the vocal folds VFs in the larynx of rabbits have been studied. VF vibrations were excited by a variable pressure air stream. We found that, at an air flow pressure of 50 to 60 mm Hg, VFs generate a white vibration noise in the frequency range of Hz to 10 kHz. The spectrum of excited vibration frequencies becomes narrower when the air flow pressure decreases from 10 to 20 mm Hg, and three discrete lower fundamental frequencies of intrinsic mechanical vibrations of individual VFs are excited at about , , and Hz, simultaneously with narrow peaks in the high-frequency region at about 3, 6, and 8 kHz, respectively. The characteristic discrete vibration frequencies of VFs are most efficiently excited near the air flow exhaustion at a pressure of 1 to 5 mm Hg.
We detected a difference in the fundamental frequencies of the excited vibrations between intact VF and those treated for a scar defect in one of the VFs. The frequencies of the lowest intrinsic excited modes of the treated VF are slightly higher compared with untreated intact VF. The mentioned frequency difference was registered with confidence and may serve as a basis for a mildly invasive instrumental diagnostics in the therapy of VF disorders as an aid to a traditional examination and subjective assessment of VF states.
It is shown that the volt—watt sensitivity of such a detector in the entire range is practically nonselective and is 2 to 10 times higher than the sensitivity of other pyroelectric detectors and the Golay cell. The bandwidth of the proposed pyrodetector was to Hz. The results showed good prospects of these sensors for fast ultrawideband spectroscopy, covering visible, infrared, terahertz, and millimeter wave ranges. Terahertz THz waves can influence a diverse range of cellular processes. The use of high-power THz sources in biological studies may lead to major advances in understanding biological systems and help to determine safe exposure levels for existing THz technologies. We are devoted to the development of an experimental system for irradiating cells with intense broadband THz pulses.
The system has been developed to allow cells to be kept in suitable conditions for long-term exposure and to be irradiated with THz pulses in single-point mode as well as in scanning mode. The transmission in the THz region of various plastic dishes for cell culture is estimated. Quantum tomography is a widely applicable tool for complete characterization of quantum states and processes. We develop a method for precision-guaranteed quantum process tomography. Our estimator is based on the Hilbert—Schmidt distance for quantum processes. Specifically, we discuss the application of our method for characterizing quantum gates of a superconducting quantum processor in the framework of the IBM Q Experience. The combined use of fluorescence diagnostics FD and photodynamic therapy PDT is a promising approach to the treatment of cholangiocarcinoma.
Information about the probing depth of laser radiation at a therapeutic dose sufficient for the appearance of the photodynamic effect allows planning the PDT process. We aim to assess the probing depth of radiation at a therapeutic dose. The highest fluorescence intensity is observed in the gall bladder and liver tissues. A significant difference was noted in the intensity of backscattered laser radiation, depending on the segments of the wild boar hepatobiliary system. The applicability of video FD of segments of the hepatobiliary system is investigated using the two-channel video fluorescence system. During video FD in the near-infrared range, the contrast of the fluorescence images of the hepatobiliary system is less than in the visible range. The results of the study will improve the quality of diagnostic information and optimize the FD and PDT algorithms for malignant neoplasms of the human hepatobiliary system.
We demonstrate the applicability of near-infrared NIR autofluorescence AF of skin tissues to differentiating neoplasms based on performing a series of experiments with in vivo and ex vivo skin tumors and analyzing the skin AF spectral shape, the excitation—emission matrices, and the photobleaching properties of malignant and benign neoplasms.
SUB-DIFFRACTION LIMIT IMAGE RESOLUTION IN THREE DIMENSIONS
We examine the validity of Eq. Sabatyan and M. We show that Eq. In particular, we show that, to agree with the implicit criterion for representing traveling waves, given when using the Fresnel—Kirchoff integral [Eq. The results obtained correcting Eq.
Bettersizer 2600
Размер частиц может быть измерен как мокрым, так и сухим методом с помощью анализатора Bettersizer Этот универсальный и мощный анализатор с модульной конструкцией и запатентованными технологиями позволяет решать самые разнообразные задачи. Пользователи могут легко и точно определять характеристики материалов размером от 0,02 мкм до мкм. Bettersizer обладает превосходной комбинацией оптических систем Фурье и инверсной Фурье. С другой стороны, в отличие от инверсной конструкции Фурье, частицы не обязательно должны лежать в одной плоскости - таким образом достигается одновременное точное измерение малых и больших частиц.
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