A system for assessing the functional state of blood flow in the skin surface layers by the speckle structure of multiply scattered optical radiation

Assessment of the parameters of skin microcirculation is an urgent and important task of modern medicine in the development of methods for diagnosing diseases of the nervous system. The system for assessing the functional state of blood flow in the skin surface layers in the wavelength range from 400 to 850 nm has been improved based on the use of an extended mathematical model of the propagation of optical radiation in human skin by taking into account additional parameters: optical anisotropy of the skin, diameter and shape of erythrocytes in the dermis layer, blood pressure in the brachial artery in the range from 90/60 to 195/130 mm·Hg, plasma protein concentration in the blood (α1, α2, β1, β2, γ-globulins and fibrinogen, g/l), rheological properties of blood flow with a diameter of blood vessels from 4.5 to 500 microns in the skin surface layers, skin temperature from +35 to +41 °C. The developed system makes it possible to determine the severity of microhemodynamic shifts in relation to metabolic disorders, improve diagnosis and evaluate the treatment efficacy of a number of neurological disorders; it also made it possible to reduce the patient examination time and increase the accuracy of measuring the blood flow microcirculation parameters by 10 % (linear and volumetric blood flow velocities) to detect blood flow disturbances in the surface layers of the skin in the normal and abnormal condition of the nervous system.

Tyramide signal amplification mass spectrometry (TSA-MS) ratio identifies nuclear speckle proteins

We present a simple ratio method to infer protein composition within cellular structures using proximity labeling approaches but compensating for the diffusion of free radicals. We used tyramide signal amplification (TSA) and label-free mass spectrometry (MS) to compare proteins in nuclear speckles versus centromeres. Our “TSA-MS ratio” approach successfully identified known nuclear speckle proteins. For example, 96% and 67% of proteins in the top 30 and 100 sorted proteins, respectively, are known nuclear speckle proteins, including proteins that we validated here as enriched in nuclear speckles. We show that MFAP1, among the top 20 in our list, forms droplets under certain circumstances and that MFAP1 expression levels modulate the size, stability, and dynamics of nuclear speckles. Localization of MFAP1 and its binding partner, PRPF38A, in droplet-like nuclear bodies precedes formation of nuclear speckles during telophase. Our results update older proteomic studies of nuclear speckles and should provide a useful reference dataset to guide future experimental dissection of nuclear speckle structure and function.

The Influence of the Speckle Structure of the Scattered Laser Radiation on the Measurement Error of the Rough Surface Vibration Displacement

The influence of the speckle structure of the scattered laser radiation on the measurement error of the rough surface vibration displacementusing laser Doppler vibrometer assembled according to a differential scheme is studied. The scheme of the experimental setup for investigation of characteristics of laser beam reflected from different surfaces is described and the obtaineed experimental images are given. It is shown that the structure of a reflected and scattered beam highly dependent on parameters of roughness of an investigated surface. Based on the results of numerical simulation, characteristic dimensions of surface irregularities are obtained, at which the beam structure is destroyed and the speckle structure is formed. It is shown that in case of a partially developed speckle structure, the error will be determined by by the relative contribution of a mirror component, a contrast and an average intensity of a speckle field. To estimate the error, a numerical simulation was performed for given parameters of a surface, beam and scatterers.

DEPENDENCE OF THE SPECKLE-PATTERNS SIZE AND THEIR CONTRAST ON THE BIOPHYSICAL AND STRUCTURAL PARAMETERS OF BIOLOGICAL TISSUES

Speckle fields are widely used in optical diagnostics of biotissues and evaluation of the functional state of bioobjects. The speckle field is formed by laser radiation scattered from the object under study. It bears information about the average dimensions of the scatterers, the degree of surface roughness makes it possible to judge the structural and biophysical characteristics of individual tissue cells (particles), on the one hand, and the integral optical characteristics of the entire biological tissue. The aim of the study was – the determination of connections between the biophysical and structural characteristics of the biotissue and the light fields inside the biotissues.The model developed of the medium gives a direct relationship between the optical and biophysical parameters of the biotissue. Calculations were carried out using known solutions of the radiation transfer equation, taking into account the multilayer structure of the tissue, multiple scattering in the medium, and multiple reflection of irradiation between the layers.With the increase wavelength, the size of speckles formed by the non-scattered component (direct light) of laser radiation increases by a factor of 2 from 400 to 800 μm in the stratum corneum and 5 times from 0.6 to 3 μm for the epidermis and from 0.27 to 1.4 μm to the dermis. Typical values of sizes of speckles formed by the diffraction component of laser radiation for the stratum corneum and epidermis range from 0.02 to 0.15 μm. For the dermis typical spot sizes are up to 0.03 μm. The speckle-spot size of the diffusion component in the dermis can vary from ±10 % at 400 nm and up to ±23 % for 800 nm when the volume concentration of blood capillaries changes. Characteristic dependencies are obtained and biophysical factors associated with the volume concentration of blood and the degree of it’s oxygenation that affect the contrast of the speckle structure in the dermis are discussed.The of speckles׳ size in the layers of tissue varies from a share of micrometer to millimeter. The established dependence makes it possible to determine the depth of penetration of light into the biotissue based on the dimensions of speckles. Calculation of the contrast of the speckle structure of scattered light in visible spectral range at different depths in the biotissue made it possible to establish the dependence of the contrast value of the interference pattern on the degree of oxygenation of the blood and the volume concentration of capillaries in the dermis.

Highly porous nanoberyllium for X-ray beam speckle suppression

This paper reports a special device called a `speckle suppressor', which contains a highly porous nanoberyllium plate squeezed between two beryllium windows. The insertion of the speckle suppressor in an X-ray beam allows manipulation of the spatial coherence length, thus changing the effective source size and removing the undesirable speckle structure in X-ray imaging experiments almost without beam attenuation. The absorption of the nanoberyllium plate is below 1% for 1 mm thickness at 12 keV. The speckle suppressor was tested on the ID06 ESRF beamline with X-rays in the energy range from 9 to 15 keV. It was applied for the transformation of the phase–amplitude contrast to the pure amplitude contrast in full-field microscopy.

Laser wakefield compression and acceleration of externally injected electron bunches in guiding structures

For the considered scheme of the external electron bunch injection in front of a laser pulse, the influence of the nonlinear driving laser pulse dynamics and electron bunch self-action to the processes of electron bunch compression and acceleration in the laser wakefield is analyzed. Self-consistent modelling results confirm that the nonlinear laser pulse dynamics limits the bunch compression due to variations of the phase velocity of the wake. A growth of the injected bunch charge leads to some extent to an increase of the trapped and accelerated bunch charge and to decrease of the trapped bunch radius and emittance due to increased self-focusing bunch. The three-dimensional theoretical model is elaborated and used to describe the propagation of laser pulses in dielectric capillary waveguides under imperfect coupling and focusing conditions with broken cylindrical symmetry. The role of cone entrances to the cylindrical part of a capillary is analyzed, and it is demonstrated that matching cones can considerably increase the transmission of laser pulses through the capillary, but cannot mitigate the requirements on the precision of the laser pulse focusing into a capillary. In order to avoid a speckle structure and strong transverse gradients of the fields, which can prevent the process of regular electron bunch acceleration, one has to ensure a small laser angle of incidence into the capillary not exceeding 1 mrad.