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

2017 ◽  
Vol 8 (2) ◽  
pp. 177-187
Author(s):  
N. D. Abramovich ◽  
S. K. Dick
Keyword(s):  
Laser Radiation ◽  
Stratum Corneum ◽  
Volume Concentration ◽  
Structural Characteristics ◽  
Structural Parameters ◽  
Scattered Light ◽  
Biological Tissues ◽  
Speckle Structure ◽  
Speckle Field ◽  
Blood Capillaries

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.

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

2019 ◽  
Author(s):  
Илья Павлов ◽  
Il'ya Pavlov ◽  
Ирина Расковская ◽  
Irina Raskovskaya ◽  
Бронюс Ринкевичюс ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Laser Radiation ◽  
Measurement Error ◽  
Rough Surface ◽  
Laser Doppler Vibrometer ◽  
Average Intensity ◽  
Speckle Structure ◽  
Vibration Displacement ◽  
Speckle Field ◽  
Surface Vibration

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.

Influence of Continuous and Pulsed Laser Radiation on Optical and Thermal Properties of Biological Tissues

2014 ◽  
Vol 59 (12) ◽  
pp. 1149-1154
Author(s):  
A.D. Mamuta ◽  
◽  
V.S. Voitsekhovich ◽  
N.M. Kachalova ◽  
L.F. Golovko ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Laser Radiation ◽  
Pulsed Laser ◽  
Biological Tissues ◽  
Pulsed Laser Radiation

scholarly journals Coupled Fluid–Solid Numerical Simulation for Flow Field Characteristics and Supporting Performance of Flexible Support Cylindrical Gas Film Seal

Aerospace ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 97
Author(s):  
Junfeng Sun ◽  
Meihong Liu ◽  
Zhen Xu ◽  
Taohong Liao ◽  
Xiangping Hu ◽  
...  
Keyword(s):  
Flow Field ◽  
Film Thickness ◽  
Fluid Dynamic ◽  
Structural Characteristics ◽  
Structural Parameters ◽  
Equivalent Stress ◽  
Three Dimensional ◽  
High Rotational Speed ◽  
Flexible Support ◽  
Flow Field Characteristics

A new type of cylindrical gas film seal (CGFS) with a flexible support is proposed according to the working characteristics of the fluid dynamic seal in high-rotational-speed fluid machinery, such as aero-engines and centrifuges. Compared with the CGFS without a flexible support, the CGFS with flexible support presents stronger radial floating characteristics since it absorbs vibration and reduces thermal deformation of the rotor system. Combined with the structural characteristics of a film seal, an analytical model of CGFS with a flexible wave foil is established. Based on the fluid-structure coupling analysis method, the three-dimensional flow field of a straight-groove CGFS model is simulated to study the effects of operating and structural parameters on the steady-state characteristics and the effects of gas film thickness, eccentricity, and the number of wave foils on the equivalent stress of the flexible support. Simulation results show that the film stiffness increases significantly when the depth of groove increases. When the gas film thickness increases, the average equivalent stress of the flexible support first decreases and then stabilizes. Furthermore, the number of wave foils affects the average foils thickness. Therefore, when selecting the number of wave foils, the support stiffness and buffer capacity should be considered simultaneously.

Synthetic Transfer Zone Characterization Using Seismic Attributes: An Example from the Parihaka Fault System in the Taranaki Basin, New Zealand.

2021 ◽  
pp. 1-73
Author(s):  
Pierre Karam ◽  
Shankar Mitra ◽  
Kurt Marfurt ◽  
Brett M. Carpenter
Keyword(s):  
New Zealand ◽  
Structural Characteristics ◽  
Structural Parameters ◽  
Seismic Attributes ◽  
Fault System ◽  
Structural Interpretation ◽  
Transfer Zones ◽  
Seismic Characterization ◽  
The Individual ◽  
Transfer Zone

Synthetic transfer zones develop between fault segments which dip in the same direction, with relay ramps connecting the fault blocks separated by the different fault segments. The characteristics of the transfer zones are controlled by the lithology, deformation conditions, and strain magnitude. The Parihaka fault is a NE-SW trending set of three major en-echelon faults connected by relay ramps in the Taranaki Basin, New Zealand. The structure in the basin is defined by extension during two episodes of deformation between the late Cretaceous and Paleocene and between the Late Miocene and recent. To better understand the evolution of a synthetic transfer zone, we study the geometry and secondary faulting between the individual fault segments in the Parihaka fault system using structural interpretation of 3D seismic data and seismic attributes. This interpretation allows for a unique application of seismic attributes to better study transfer zones. Seismic attributes, including coherence, dip, and curvature are effective tools to understand the detailed geometry and variation in displacement on the individual faults, the nature of secondary faulting along the transfer zones, and the relationship between the faults and drape folds. Seismic characterization of the fault system of Miocene to Pliocene age horizons highlights variations in the degree of faulting, deformation, and growth mechanism associated with different stages of transfer zone development. Coherence, dip, and curvature attributes show a direct correlation with structural parameters such as deformation, folding, and breaching of relay ramps.. All three attributes enhance the visualization of the major and associated secondary faults and better constrain their tectonic history. The observed correlation between seismic attributes and structural characteristics of transfer zones can significantly improve structural interpretation and exploration workflow.

scholarly journals Numerical simulation of changes in the electric properties of biological tissues under local heating by laser radiation

2021 ◽  
Vol 2090 (1) ◽  
pp. 012049
Author(s):  
N V Kovalenko ◽  
A V Smirnov ◽  
O A Ryabushkin
Keyword(s):  
Numerical Simulation ◽  
Mathematical Model ◽  
Laser Radiation ◽  
Optical Radiation ◽  
Local Heating ◽  
Biological Tissues ◽  
Electric Properties ◽  
Reliable Tool ◽  
The Mathematical Model

Abstract The mathematical model that describes the local heating of biological tissues by optical radiation is introduced. Changes of the electric properties of biological tissues in such process can be used as a reliable tool for analyzing heating and damage degrees of tissues.

scholarly journals Influence of parameters of impulse laser impact on the formation of the gradient of the structure of porous titanium powder

2018 ◽  
pp. 88-94
Author(s):  
D. V. Minko
Keyword(s):  
Laser Radiation ◽  
Titanium Powder ◽  
Structural Characteristics ◽  
Selective Laser Sintering ◽  
Light Flux ◽  
Laser Action ◽  
Pulsed Laser ◽  
Powder Materials ◽  
Solid Core ◽  
Powder Particles

The possibility of selective laser sintering of graded porous and compactly porous structures by surface fusion of powder particles is demonstrated while maintaining a solid core, which leads to the formation of interparticle contacts in the presence of a liquid phase. The interaction of the light flux of the laser pulse with the surface of the powder particles under multiple reflection is considered. It is shown that the effect of single pulses of laser radiation leads to the formation of sintered structural elements of a powder material having a diameter approximately equal to the diameter of the focal spot. Technological regimes of pulsed laser action are established at which steady contact formation of titanium powder particles of the fractional compositions under study occurs. The possibility of obtaining powder materials with a gradient structure by controlling the parameters of pulsed laser action is experimentally demonstrated. It was found that accurate dosing of thermal energy and the number of pulses of laser radiation makes it possible to minimize shrinkage of powder layers in the absence of particle conglomeration, to control the structural characteristics and properties of products, to preserve the microstructure and phase composition of the initial materials.

Action Mechanisms of Laser Radiation in Biological Tissues

2003 ◽  
pp. 73-127 ◽  
Author(s):  
A. Roggan ◽  
U. Bindig ◽  
W. Wäsche ◽  
F. Zgoda ◽  
R. Steiner ◽  
...  
Keyword(s):  
Laser Radiation ◽  
Biological Tissues ◽  
Action Mechanisms

Abstract TP436: Dysfunctional Cerebral Neovascularization And Remodeling Patterns In Obese And Lean Models Of Type 2 Diabetes

Stroke ◽  
2013 ◽  
Vol 44 (suppl_1) ◽  
Author(s):  
Roshini Prakash ◽  
Maribeth Johnson ◽  
Susan C Fagan ◽  
Adviye Ergul
Keyword(s):  
Type 2 Diabetes ◽  
Glycemic Control ◽  
Structural Characteristics ◽  
Structural Parameters ◽  
Volume Density ◽  
3 Dimensional ◽  
Gk Rats ◽  
Dimensional Reconstruction ◽  
Branch Density

We previously reported intense pial cerebral collateralization and arteriogenesis in a mild and lean model of type 2 diabetes, Goto-Kakizaki (GK) rats. Further 3-dimensional fluroscein (FITC) imaging studies revealed regional differences in increased cerebral neovascularization which was associated with poor vessel wall maturity. Building upon these findings, the goals of this study were a) to compare and contrast this pathological neovascularization pattern in db/db mice and GK models of diabetes, and b) determine the effect of glycemic control on erratic cerebral neovascularization. Total vascular volume, density and surface area as well as structural parameters including microvessel/macrovessel ratio, non-FITC perfusing vessel abundance, penetrating arteriole (PA) branching density and diameter, and tortuosity were measured by 3 dimensional reconstruction of FITC stained vasculature using Z-stacked images obtained with confocal microscopy. Lean GK rats exhibited an increase in both micro and macrovessel density, non-perfusing vessel abundance, branch density, diameter and tortuosity. Glycemic control with metformin prevented these changes. Obese db/db mice, on the other hand, showed an increase in only microvascular density but this was not associated with an increase in non-FITC perfusing vessels. PA branch density was higher than controls but branch diameter was reduced. Diabetes also promoted astrogliosis. These results suggests that type 2 diabetes leads to cerebral neovascularization and remodeling but structural characteristics of newly formed vessels differ between lean and obese models that have mild or severe hyperglycemia, respectively. The prevention of dysfunctional cerebral neovascularization by early glucose control suggests that hyperglycemia is a mediator of this response. N=4-8 * p≤ 0.05, ** p≤ 0.005 *** 0.0005

Optimal Design of Composite Material Maintenance Structure for Aircraft Based on ANSYS Workbench

2021 ◽  
Vol 871 ◽  
pp. 216-221
Author(s):  
Jing Tao Dai ◽  
Pei Zhong Zhao ◽  
Hong Bo Su ◽  
Hao Dong Liu ◽  
Yu Bo Wang ◽  
...  
Keyword(s):  
Finite Element ◽  
Composite Material ◽  
Optimal Design ◽  
Structural Characteristics ◽  
Structural Parameters ◽  
Element Model ◽  
Composite Cement ◽  
Composite Patch ◽  
Length Width ◽  
Ansys Workbench

Composite material is widely used to maintain damaged structures of aircraft. The 3D finite element model of composite cement maintenance for aircraft is established by finite element method software ANSYS Workbench. The structural characteristics and usage status of the composite cement maintenance model is analyzed, and then the optimal structural parameters of the composite patch are obtained, including the length, width and thickness. The results show that the composite cement maintenance method could effectively restore the rigidity, and improve the strength of the structure. Furthermore, the optimal design for composite patch ensures safety of aircraft, economics of maintenance, and operability of repair methods.

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