Wall Elasticity Research Articles

Infrared study and computational simulations of coronary arteries atherosclerotic lesions for early diagnosis of disease progression

Abstract Introduction Coronary artery atherosclerotic disease is the most common cardiovascular disease and bypass grafting surgery (CABG) is an effective treatment. However, the pathogenic mechanism of coronary arteries atherosclerosis and disease progression is not yet clear. Purpose The use of FT-IR spectroscopy, hyperspectral microscope and mathematical simulation models are some of the tools to predict the morphological and elasticity disorders in the vessel wall due to molecular structure changes. Methods Biopsies of atherosclerotic native coronary arteries from 54 patients (44–85 years), who underwent coronary endarterectomy during bypass grafting surgery (CABG), were examined ex vivo. The FT-IR-spectra were recorded with a Nicolet-6700 spectrometer. Morphological changes of atheromatic plaques were performed with SEM-EDX, Fei-Co. CytoVita-Olympus hyperspectral microscope was used to obtain the cells. Results FT-IR spectroscopy (Figure 1A) showed that the disease affects the protein folding, leading to amyloid formation (beta-sheets), lipid peroxidation and AGEs (Advanced Glycation end products) production. The detection of amorphous CaCO3 (1415 and 872 cm–1) deposits in high lipophilic regions was of high importance. Increased mineral concentration leads to increased formation of crystalline deposits, consisting of CaCO3, CaHPO4, Ca3(PO4)2 and inorganic hydroxyapatite, resulting in arterial stenosis. Hyperspectral images confirmed the formation of micelles (1) due to amyloidosis and calcified cells (2), in agreement with FT-IR, ImageJ analysis data. Mathematical simulation model based on finite element method (Figure 1E) showed that arterial wall damage and elasticity changes were not homogenous. This model provides the time of crystallization of the calcium salts, which play crucial role to stenosis. Conclusions FT-IR spectra showed that the formation of amorphous CaCO3 in the presence of Mg2+, in reach of oxidized lipids regions, inhibit the development of coronary artery stenosis. Excessive of Ca2+ efflux promotes the crystallinity of CaCO3 and Ca3(PO4)2 deposits, leading to the development of atherosclerotic plaques and coronary artery stenosis. Mathematical models approach in a much better way the progression of arterial atherosclerosis. Funding Acknowledgement Type of funding sources: None. Figure 1

Clinical and Prognostic Value of Vascular Wall Elasticity in Pregnant Women with Arterial Hypertension: A Review

In recent years, the attention of many researchers around the world has been focused on studying the risks associated with the development of the pathological course of pregnancy in women with arterial hypertension (AH). The pathogenesis of gestational complications is complex and is largely associated with endothelial dysfunction, changes in the structure and properties of the vascular wall and a decrease in its elasticity. At the same time, at the present stage, a high prognostic value of the assessment of vascular elasticity in the development of cardiovascular disasters in patients with hypertension in the general population has been proved. In order to predict the risk of gestational complications early, it is promising to study the state of elasticity of the vascular wall, which will optimize the management of pregnancy and improve perinatal outcomes in pregnant women with hypertension. The literature search was carried out by keywords using the Scopus, Web of Science, Cyber Leninka, RSCI (Russian Science Citation Index) systems.

Evaluation of Lung Aeration and Respiratory System Mechanics in Obese Dogs Ventilated With Tidal Volumes Based on Ideal vs. Current Body Weight.

We describe the respiratory mechanics and lung aeration in anesthetized obese dogs ventilated with tidal volumes (VT) based on ideal (VTi) vs. current (VTc) body weight. Six dogs with body condition scores ≥ 8/9 were included. End-expiratory respiratory mechanics and end-expiratory CT-scan were obtained at baseline for each dog. Thereafter, dogs were ventilated with VT 15 ml kg−1 based on VTi and VTc, applied randomly. Respiratory mechanics and CT-scan were repeated at end-inspiration during VTi and VTc. Data analyzed with linear mixed models and reported as mean ± SD or median [range]. Statistical significance p < 0.05. The elastance of the lung, chest wall and respiratory system indexed by ideal body weight (IBW) were positively correlated with body fat percentage, whereas the functional residual capacity indexed by IBW was negatively correlated with body fat percentage. At end-expiration, aeration (%) was: hyperaeration 0.03 [0.00–3.35], normoaeration 69.7 [44.6–82.2], hypoaeration 29.3 [13.6–49.4] and nonaeration (1.06% [0.37–6.02]). Next to the diaphragm, normoaeration dropped to 12 ± 11% and hypoaeration increased to 90 ± 8%. No differences in aeration between groups were found at end-inspiration. Airway driving pressure (cm H2O) was higher (p = 0.002) during VTc (9.8 ± 0.7) compared with VTi (7.6 ± 0.4). Lung strain was higher (p = 0.014) during VTc (55 ± 21%) than VTi (38 ± 10%). The stress index was higher (p = 0.012) during VTc (SI = 1.07 [0.14]) compared with VTi (SI = 0.93 [0.18]). This study indicates that body fat percentage influences the magnitude of lung, chest wall, and total respiratory system elastance and resistance, as well as functional residual capacity. Further, these results indicate that obese dogs have extensive areas of hypoaerated lungs, especially in caudodorsal regions. Finally, lung strain and airway driving pressure, surrogates of lung deformation, are higher during VTc than during VTi, suggesting that in obese anesthetized dogs, ventilation protocols based on IBW may be advantageous.

Development of a water-filled four-sensor impedance tube

Four-sensor impedance tubes are readily utilized for characterization of the acoustic properties of materials in a gaseous host medium, as described in the standard ASTM E2611-19. Similar acoustic characterization is desired for materials submersed in water. Previous studies have documented the challenges of performing measurements in water-filled impedance tubes due to interaction with the elastic tube wall and difficulty in obtaining a suitable end-termination condition. Building upon previous demonstration of a two-sensor water-filled impedance tube [J. Acoust. Soc. Am. 113, 3245 (2003)], this paper discusses the development and demonstration of a four-sensor water-filled impedance tube with an anechoic termination. The technique utilizes two sensors on each side of the test section to simultaneously characterize both the incident and transmitted standing wave field and extract the complex impedance and wavenumber from the test sample. Discussion will focus on the challenges of performing such measurements in a water-filled tube along with methods for overcoming these challenges. Validation measurements of homogeneous materials in the 1–10 kHz band will be presented to demonstrate that both the complex impedance and wavenumber of a material submersed in water can be extracted using this approach. [Work supported by ONR.]

Measurement of the arterial wall elasticity using the velocity of flexural waves in retinal blood vessels

Arterial stiffness (typically a Young modulus of 100 kPa) is known to be an indicator of the cardiovascular health of a patient. It is commonly used in clinics to prevent and anticipate cardiovascular diseases. The existing methods allowing to measure the arterial wall elasticity measuring the velocity of the natural pulse wave lack of accuracy. We propose here a method consisting in using laser Doppler holography experiments to estimate the arterial wall elasticity. Laser Doppler holography experiments are performed on patients and noise correlation algorithms are used on these data to measure the wave velocity. We measured separately the wavelength and the frequency of elastic waves, allowing to calculate their velocity. Due to the temporal resolution of the raw data and to the way the data are processed, the waves we detected are not the classical axisymmetric pulse wave. The physics of guided waves indicates that both antisymmetric (called A0) and symmetric (called S0) waves can propagate in tubes, and in this case only antisymmetric flexural waves are detected. They are both sensitive to the arterial wall elasticity, and at low frequencies, flexural (or antisymmetric) waves are much slower than the axisymmetric pulse wave, about 3 mm/s, allowing to increase greatly the measurement accuracy. When knowing the diameter of the blood vessel, for the first time it is possible to retrieve the arterial wall elasticity thanks to the antisymmetric wave velocity measurement.

Subclinical hypothyroidism: do you always need hormone replacement therapy? A modern view of the problem

Subclinical hypothyroidism is the initial stage of development of hypothyroidism, in which there are no clear clinical symptoms and there is a slow decline in thyroid function. It is known that subclinical hypothyroidism occurs in the population much more often than overt one, its prevalence depends on gender, age of patients and it is much more often diagnosed in elderly women. The literature review considers the effectiveness of the combined herbal preparation to improve the quality of life in hypothyroidism — Endomar, which contains 50 % of Potentilla alba, 25 % of Skutellaria baicalensis and 25 % of Rhodiola rosea. All three components of Endomar are synergistic in hypothyroidism. This multicomponent herbal product has a wide range of therapeutic properties and can be recommended for subclinical forms of thyroid hypofunction. Potentilla alba has been used in medical practice since ancient times. Biologically active components of Potentilla alba extract are flavonoids that regulate the permeability and elasticity of blood vessel walls, thereby neutralizing free radi-cals, phenolcarboxylic acids having antimutagenic and diuretic properties, saponin glycosides, which have a cardiotonic, neurotropic effect, hypocholesterolemic, adaptogenic, sedative action. Rhodiola rosea, an extract of the roots and rhizomes of this plant, is an adaptogen that increases the body’s resistance to stress, exhaustion, fatigue. Rhodiola rosea includes the following active substances: phenols and their derivatives aurol, salidroside; flavonoids: kaempferol, rhodiolin, rhodionin, rhodiosine, trace elements. Endomar includes Skutellaria baicalensis, which has unique properties. This plant contains flavonoid baicalin, which has a neuroprotective and neotropic effect, flavonoids scutellarin and vagonin that maintain normal vascular tone. In general, all components have an antioxidant, antispasmodic, antiinflammatory effect, they are also adaptogens and include trace elements such as magnesium, zinc, selenium.

Effect of plaque geometry on targeted delivery of stem cells containing magnetic particles in a rigid and elastic curved artery with stenosis

Magnetic drug targeting (MDT) is a new and effective therapeutic technique to treat some diseases. In this method, the transfer of magnetic particles labeled with therapeutic agents in the presence of a magnetic field increases the efficiency of treatment. In this study, targeted delivery of endothelial cells containing magnetic particles in a stenosed curved artery for solid and elastic wall states was investigated, using an external magnetic field. The Eulerian-Lagrangian approach and the Eulerian-Lagrangian coupled FSI technique were employed to solve the continuum equations and track the trajectory of cells in a rigid and elastic artery, respectively. The influence of parameters was investigated, such as the mass of magnetic particles injected in each cell, the magnetic field strength, the injection time, the occlusion percentage, and the chord length of stenosis on the capture efficiency (CE). The effect of wall elasticity on CE was also studied. The results reveal that by increasing the mass of magnetic particles injected in each cell from 20 pg to 300 pg, the cells absorption at the target site is enhanced from 17% to 43%. Also, a slight increase in the magnetic field strength has a significant effect on increasing the CE. The injection of cells in a complete period of the cardiac cycle provides greater CE than other systole and diastole intervals. Examining the stenosis morphology shows that reducing the occlusion percentage from 40% to 20% and the chord length of stenosis from 70° to 30° results in an increase in the CE about 6% and 3% for 300 pg of magnetic particles in each cell, respectively. The trend of CE changes is the same for elastic artery and the rigid artery. However, in all cases, the elastic artery has a higher CE than the rigid artery. The obtained results can be useful for the treatment of atherosclerosis in curved vessels using targeted cell delivery.

Abstract P247: Elastin Insufficiency Impairs Renal Hemodynamics And Accelerates Aging-associated Structural And Functional Remodeling Of Preglomerular Arterioles

Elastin degradation and fragmentation are hallmarks of arterial stiffness and renal dysfunction associated with aging. However, it is unclear whether elastin insufficiency contributes to the changes in the structure and function of the resistance vasculature of the kidney during aging. Here we determined how increased vascular stiffness due to elastin insufficiency alters renal hemodynamics and mechanical properties of preglomerular arterioles. We assessed renal hemodynamics under anesthesia in 14-16-month-old female wild type (WT) and elastin heterozygous ( Eln +/- ) mice. Renal autoregulation was assessed by a stepwise increase in renal perfusion pressure (RPP) by simultaneously occluding the superior mesenteric and celiac arteries. Myogenic constriction and arterial stiffness were assessed by pressure myography of isolated renal interlobar arteries. Baseline renal vascular resistance (RVR) was elevated in Eln +/- mice (13.8 ± 2.9 vs 11.2 ± 1.4 mmHg/μL/min/g left kidney weight), while systolic blood pressure (SBP; 75.1 ± 7.4 vs 91 ± 4.2mmHg), renal blood flow (RBF; 6.3 ± 1.2 vs 7.4 ± 1.7 μL/min/g left kidney weight), renal plasma flow (RPF; 3.4 ± 0.8 vs 5 ± 1.2 mL/min/g/ left kidney weight) and urine flow rate, all trended lower in Eln +/- mice compared to WT mice. Glomerular filtration rate (GFR) and filtration fraction (FF) were similar between the two groups. A stepwise increase in RPP caused a slower decline and rise in RBF and RVR, respectively, in Eln +/- relative to WT mice. The maximal changes in RBF (5 ± 1.1 vs 4.7 ± 0.8 μL/min/g left kidney weight), RVR (17.6 ± 7.3 vs 22.5 ± 2.1 mmHg/μL/min/g left kidney weight), urine flow rate,GFR, and FF were less robust in Eln +/- mice. RPF decreased in WT mice in response to raising RPP, whereas it remained unchanged in Eln +/- mice. Myogenic response and increases in elastic modulus and wall tension following stepwise changes in intraluminal pressure were all augmented in interlobar arteries from Eln +/- relative to WT mice. However, there was no difference in kidney weight/tibia length ratio between the two genotypes. We conclude that elastin insufficiency impairs renal hemodynamics by exacerbating age associated increase in vascular stiffness.

Different Approaches for Manufacturing Ti-6Al-4V Alloy with Triply Periodic Minimal Surface Sheet-Based Structures by Electron Beam Melting.

Targeting biomedical applications, Triply Periodic Minimal Surface (TPMS) gyroid sheet-based structures were successfully manufactured for the first time by Electron Beam Melting in two different production Themes, i.e., inputting a zero (Wafer Theme) and a 200 µm (Melt Theme) wall thickness. Initial assumption was that in both cases, EBM manufacturing should yield the structures with similar mechanical properties as in a Wafer-mode, as wall thickness is determined by the minimal beam spot size of ca 200 µm. Their surface morphology, geometry, and mechanical properties were investigated by means of electron microscopy (SEM), X-ray Computed Tomography (XCT), and uniaxial tests (both compression and tension). Application of different manufacturing Themes resulted in specimens with different wall thicknesses while quasi-elastic gradients for different Themes was found to be of 1.5 GPa, similar to the elastic modulus of human cortical bone tissue. The specific energy absorption at 50% strain was also similar for the two types of structures. Finite element simulations were also conducted to qualitatively analyze the deformation process and the stress distribution under mechanical load. Simulations demonstrated that in the elastic regime wall, regions oriented parallel to the load are primarily affected by deformation. We could conclude that gyroids manufactured in Wafer and Melt Themes are equally effective in mimicking mechanical properties of the bones.

Changes in Hemodynamic Parameters in Various Morphological Changes in the Kidney Transplant in Children

Ultrasound scanning is one of the main methods of instrumental examination of patients after allogenic transplantation of kidney. The main reasons of dysfunction of the kidney transplant in long posttransplantation term are acute or chronic rejection, as well as acute and chronic nephrotoxicity of calcineurin inhibitors. The study includes an analysis of the medical history of 130 children with end-stage chronic renal failure who underwent 130 allogeneic kidney transplants from a posthumous donor. There were analyzed the results of 231 percutaneous puncture biopsies and ultrasound studies of renal transplants. The analyzed data of morphological studies are divided into 4 groups:1st group — there are no morphological changes affecting graft function;2nd group — morphological signs of calcineurin toxicity;3rd group — borderline damage of the graft;4th group — acute and chronic graft rejection;5th group — non-specific tubulointerstitial sclerosis and tubular atrophy.Indices of resistance and pulsation measured at the level of the renal artery and interlobular arteries tended to decrease in the kidneys with immunological influence and remained stable in other morphological groups. This means that, the higher the degree of hyalinosis of the arteries, the lower the indices of resistance and pulsation indices measured at the level of the common renal artery and interlobular arteries. The revealed tendency of a decrease in the values of the resistance index and the pulsation index at the level of the common renal artery of the interlobular arteries can be considered as one of the initial ultrasound signs that allow to speak of a decrease in the elasticity of the vascular wall. Normal indices of renal hemodynamics do not exclude the presence of pathological processes leading to graft dysfunction.

Influence of the inclination angle on the sound field in an irregular enclosure containing two elastic walls

The sound field model of an irregular enclosure with two elastic walls and an inclined wall is established by the modal theory. The modal parameters of the irregular enclosure are obtained by the envelope rectangular technique. The influence of the inclination wall angle on the sound field in the irregular enclosure is discussed. When the inclination angle is increased from 0° to 45°, the resonance frequencies of the acoustic enclosure are basically reduced in the frequency range of 0∼250 Hz. When the inclination angle is increased from 0° to 45° every 15° interval, the amplitude of a certain acoustic mode itself decreases, while the amplitudes of the acoustic modes coupled to it basically increase. The acoustic potential energy peaks in the enclosure basically shift to the low frequency with the increase of the inclination angle. Furthermore, the change trend of the acoustic potential energy is regular in the low-order modes, but relatively chaotic in the high-order modes. In addition, in order to verify that the accurate description of the primary sound field is the basis of effective noise control, the two-elastic plate model is deliberately treated as one-elastic plate model, and its influence on the performance of active noise control is discussed. Also, if the multi-elastic plate model is regarded as a simplified automobile cab, the research results can be used for the preliminary acoustic design of the cab; that is, the research results can be used for the acoustic design of similar models.

Leveraging Elasticity to Uncover the Role of Rabinowitsch Suspension through a Wavelike Conduit: Consolidated Blood Suspension Application

The present work presents a mathematical investigation of a Rabinowitsch suspension fluid through elastic walls with heat transfer under the effect of electroosmotic forces (EOFs). The governing equations contain empirical stress-strain equations of the Rabinowitsch fluid model and equations of fluid motion along with heat transfer. It is of interest in this work to study the effects of EOFs, which are rigid spherical particles that are suspended in the Rabinowitsch fluid, the Grashof parameter, heat source, and elasticity on the shear stress of the Rabinowitsch fluid model and flow quantities. The solutions are achieved by taking long wavelength approximation with the creeping flow system. A comparison is set between the effect of pseudoplasticity and dilatation on the behaviour of shear stress, axial velocity, and pressure rise. Physical behaviours have been graphically discussed. It was found that the Rabinowitsch and electroosmotic parameters enhance the shear stress while they reduce the pressure gradient. A biomedical application to the problem is presented. The present analysis is particularly important in biomedicine and physiology.

Arterial Stiffness in Type 1 Diabetes: The Case for the Arterial Wall Itself as a Target Organ.

Arterial stiffness (AS) integrates the cumulative burden of known and unknown cardiovascular risk factors on the elastic wall of large arteries along the lifespan of an individual. As a marker of vascular aging, AS is an independent predictor of cardiovascular events and improves cardiovascular risk prediction when added to the Framingham Risk Score. In addition, AS may affect the microvasculature and promote the development of microvascular complications. Its impact on both the macro- and microvasculature has led to the concept that the arterial wall itself should be considered as a target organ. Here, we review the biological and clinical consequences of AS on the macro- and microvasculature and the measurement of AS in routine clinical practice. We also discuss the pathophysiological mechanisms underpinning AS development using diabetes and, in particular, type 1 diabetes, as a disease model with a high risk of cardiovascular events and microvascular complications that are accelerated by AS.

Character of β-lymphocytes differentiation in women with hypertensive disorders during pregnancy.

The aim of the work was to identify the features of B-lymphocyte differentiation in women with hypertensive disorders of various origins, to establish their relationship with indicators of the elastic properties of the vascular wall, and to develop additional diagnostic criteria for the severity of preeclampsia. We examined 193 women at 24-40 weeks of gestation. Of these, 39 women with chronic arterial hypertension, 35 women with preeclampsia that developed against the background of chronic arterial hypertension, 55 with preeclampsia. The control group consisted of 64 women without hypertensive disorders. To assess the elastic properties of the vascular wall, a sphygmographic attachment of the "Poly-Spectrum-8" hardware-software complex ("Neurosoft" Ivanovo) was used. The relative content of B-lymphocytes (CD19 + and CD20 +), regulatory B-cells (CD20 + IL-10 +), switched (CD19 + CD27 + IgD-) and non-switched (CD19 + CD27 + IgD +) memory cells, plasma cells (CD19 + CD20-CD38 +) in the general population of B-lymphocytes was assessed by flow cytometry on a FACSCantoII flow cytometer using the FACS Diva program. Statistical analysis was carried out using the programs "Statistica for Windows 6.0", "Microsoft Excel 2010" and "MedCals". All subjects with hypertensive disorders showed an increase in the stiffness of the arteries of the muscular and elastic types, the most pronounced in the groups of patients with PE, the maximum in women with CAH and associated PE. An increased level of B1-lymphocytes in the peripheral blood is also noted in all hypertensive disorders. There were revealed positive correlations of high strength between: the level of CD20 + cells and the velocity of pulse wave propagation through the arteries of the muscular type (PWVm) in all groups with hypertensive disorders; the content of B1 cells and PWVM in moderate preeclampsia; level emory B-cells and PWV in elastic-type arteries in women with CAH and associated PE. The ROC analysis of the relative content of B1 cells in the general population of B lymphocytes and the content of IL-10-producing cells in the population of CD20 + lymphocytes (Breg) in women with moderate and severe PE revealed criteria for the differential diagnosis of preeclampsia of varying severity. The presence of hypertensive disorders of various origins is accompanied by a decrease in the elasticity of the arterial vascular wall, which is most pronounced in patients with CAH and associated PE. These changes are largely correlated with the level of B cells. As additional criteria for determining the severity of PE, the relative content of B1 cells and IL-10-producing cells in the population of Breg CD20 + lymphocytes can be used.

Radius evolution for bubbles with elastic shells

We present an analysis of an extended Rayleigh–Plesset (RP) equation for a three dimensional cell of microorganisms such as bacteria or viruses in some liquid, where the cell membrane in bacteria or the envelope (capsid) in viruses possess elastic properties. To account for rapid changes in the shape configuration of such microorganisms, the bubble membrane/envelope must be rigid to resist large pressures while being flexible to adapt to growth or decay. Such properties are embedded in the RP equation by including a pressure bending term that is proportional to the square of the curvature of the elastic wall. Analytical solutions to this extended equation are obtained in terms of elliptic functions.

Stability and the transition to turbulence in the flow through conduits with compliant walls

The mechanisms of destabilisation of the flow through soft-walled channels/tubes are qualitatively different from those in rigid-walled conduits. The stability depends on two dimensionless parameters, the Reynolds number $(\rho _f V_f h_f/ \mu _f)$ and $\varSigma = (\rho _f G h_f^{2}/\mu _f^{2})$ , where $\rho _f$ and $\mu _f$ are the fluid density and viscosity, $h_f$ and $V_f$ are the fluid length and velocity scale and $G$ is the wall elasticity modulus. There is an instability at zero Reynolds number when the dimensionless parameter $\varGamma = (\mu _f V_f / h_f G)$ exceeds a critical value. The low-Reynolds-number instability of the Couette flow past a compliant surface is well understood, and has been confirmed in experiments, but that in a pressure-driven flow is not completely understood. Two modes of instability at high Reynolds number have been predicted: the inviscid mode with an internal viscous layer, for which the transition Reynolds number scales as ${Re}_t \propto \varSigma ^{1/2}$ ; and the wall mode instability with a viscous layer at the wall, for which ${Re}_t \propto \varSigma ^{3/4}$ . The wall mode instability has been observed in experiments at Reynolds number as low as 300 in a soft-walled tube and as low as 100 in a channel with one compliant wall, though the scaling of the transition Reynolds number differs from the theoretical prediction due to substantial wall deformation. Though the flow after transition shares many of the characteristics of hard-wall turbulence, it differs in significant ways, suggesting that soft-wall turbulence is a separate class distinct from hard-wall turbulence.

Fixed combination of ramipril and indapamide in patients with hypertension and non-alcoholic fatty liver disease: focus on the large arteries

Objective.To assess the effect of antihypertensive therapy with ramipril and indapamide on the elasticity of the vascular wall of the large arteries in relation to insulin resistance and chronic low-intensity inflammation in patients with hypertension (HTN) and non-alcoholic fatty liver disease (NAFLD).Design and methods.An open prospective controlled study was conducted: 30 patients with HTN stage I–II in combination with NAFLD (Fatty Liver Index (FLI) &gt; 60) at the age of 45–65 years were included. Washout period was scheduled 5–7 days before the baseline examination, followed by the prescription of one of the fixed combinations of ramipril (2,5/5 mg/day) and indapamide (0,625/1,25 mg), depending on the required dosage (Konsilar-D 24 VERTEX AO, Russia) and were given recommendations on lifestyle changes and weight loss. A clinical examination was carried out, indicators of daily blood pressure (BP) monitoring and central aortic pressure (CAP), pulse wave velocity (PWV), lipid and carbohydrate metabolism, chronic low-intensity inflammation and the severity of insulin resistance before and after treatment were analyzed.Results.After 24-week therapy with a fixed combination of ramipril and indapamide at an average dosage of 4,04 ± 1,24 and 1,01 ± 0,31 mg, respectively, 100% of patients with HTN and NAFLD achieved target BP levels. According to 24-hour BP monitoring data, a significant decrease in systolic BP (SBP) and diastolic BP (DBP) was observed, both in the daytime (Δ12 mm Hg, р = 0,0001; Δ5,5 mm Hg, р = 0,0019, respectively), and at night (Δ13,5 mm Hg, р = 0,0006; Δ5,5 mm Hg, р = 0,0054, respectively). In addition, there was a significant decrease in CAP in the daytime (SBPao p = 0,0011, DBPao p = 0,0022) and night hours (SBPao p = 0,0015, DBPao p = 0,00124), and a statistically significant decrease in augmentation index (day p = 0,0460, night p = 0,0182). When evaluating clinical data and bioimpedance measurements, a decrease in waist circumference (p = 0,0000), hip circumference (p = 0,0001), the proportion of subcutaneous (p = 0,0134) and visceral (p = 0,0019) fat was found, which may indicate a decrease in the severity of visceral obesity. Also, during treatment, there is a decrease in the severity of insulin resistance (and the concentration of tumor necrosis factor alpha (TNF-α) (p &lt; 0,0001) and CRP (p = 0,0002) in blood plasma. Finally, fixed combination of ramipril and indapamide led to a significant decrease in vascular stiffness (p = 0,0166) and a decrease in the proportion of patients with PWV paradoxical test (p = 0,0320). Correlation analysis showed that increased stiffness of the large arteries in patients with HTN and NAFLD is closely related to insulin resistance and lipid metabolism. At the same time, after 24-week therapy by a fixed combination of ramipril and indapamide, a decrease in the vascular stiffness in patients with HTN and NAFLD significantly correlated with the TNF-α concentration.Conclusions.A 24-week therapy by the fixed combination of ramipril and indapamide iin patients with HTN and NAFLD is associated with the persistent decrease in BP and CAP, both during the day and at night. There was a decrease in the vascular rigidity in muscular arteries. The treatment and recommendations for changing the lifestyle are associated with the decrease in the severity of abdominal obesity and insulin resistance, as well as the decrease in the severity of low-intensity systemic inflammation in patients with HTN and NAFLD, and a significant correlation was established between a decrease in TNF-α and an increase in the vascular elasticity of muscle and elastic type arteries.

The Mechanical Effect of Pit Excavation with Protection on Adjacent Pipelines

The normal operation of pipelines will be affected by the surrounding environment. As an outstanding problem, pit excavation with protection on adjacent pipelines has been paid more and more attention in urban infrastructure. Adding retaining structure in soft clay area can effectively reduce the influence of pit excavation on buried pipeline. In this paper, a3D simulation model of pipeline-soil-wall coupling is established. And the effect parameters of soil, pipeline and envelope on pipeline stress distribution, axial strain and pipeline displacement are analysed. It is found that the stress of pipeline concentrated on the middle part of the pipeline after excavation with retaining foundation pit. The larger the elastic modulus and cohesive force of soil, the smaller the deformation of pipeline, while the change of Poisson’s ratio is opposite. With the increase of pipeline wall thickness and distance between pipeline and diaphragm wall, the Poisson’s ratio is decreased. The internal pressure of the pipeline has hardly affected by the deformation of pipeline, but the deformation of pipeline is increased with the increase of the depth of the foundation pit. The thickness and modulus of elasticity of diaphragm wall have the same change. They are greater with the smaller of deformation capacity of pipeline. These results provide theoretical guidance for the research of foundation pit and pipeline, and provide reference basis for engineering construction.

Stress distribution in the walls of major arteries: implications for atherogenesis.

There is a correlation between the sites of atheroma development and stress points in the arterial system. Generally, pulse pressure results in stresses acting on the vascular vessel, including longitudinal stress, radial or normal stress, tangential stress or hoop stress and shear stress. This paper explores the relationship between arterial wall shear stress and pulsatile blood pressure with the aim of furthering the understanding of atherogenesis and plaque progression. We computed the magnitude of the shear stresses within the carotid bifurcation geometry of a patient and calculated the increase in shear stress levels that would occur when the blood pressure and pulse pressures rise during exertion. We also determined in which layer of the artery wall the maximum shear stress is located, and computed the shear stress at different levels within the media. We used the theory of laminate analysis, (Classical Laminate Plate Theory), to analyse the stress distribution on the carotid artery wall. Computational Fluid Dynamics (CFD) analysis was used on anatomy based on a CT angiogram of the carotid bifurcation of a patient with a 90% stenosis on the right side and 10% on the left. The pulsatile non-Newtonian blood flow with a resting blood pressure of 120/80 mmHg and an exertion pressure of 200/100 mmHg was simulated and the resultant forces were transferred to an ANSYS Composite PrepPost (ACP) model for wall shear stress analysis. A multilayer elastic, anisotropic, and inhomogeneous arterial wall (intima, internal elastic lamina, media, external elastic lamina, and adventitial layers) was modelled and the shear stress magnitudes and change over time between the layers was calculated. Shear stress in the individual composite layers is far greater than that acting on the endothelium (less than 5 Pa). At rest, the maximum variation of shear stress in the arterial wall occurs in the intima (138 Pa) and adventitia (135 Pa). The medial layer has the lowest variation of shear stress. Under severe exertion, the maximum shear stress magnitude in the intimal layer and the adjacent medial layer is near the ultimate stress level. The maximum/minimum shear stress ratios during the cardiac cycle vary most widely in the innermost part of the media, adjacent to the intima, with a four-fold ratio increase. This compares with a less than two-fold increase in all the other layers including the intima and adventitia, making the inner media the most vulnerable layer to mechanical injury. This study showed that the magnitude of exertion-induced shear stress approaches the ultimate stress limit in the intima and the immediate adjacent medial layer. The variation in stress is maximal in the inner layer of the media. These findings correlate the site of atheroma development with the most vulnerable site for injury in the media and emphasise the impact of pulse pressure. Further biological studies are required to ascertain whether this leads to injury that initiates atheroma that then precipitates an injury/healing cycle.

Hydrodynamic model of blood flow in major arteries pulsing in various modes.

Traditionally, the arteries in mammals are viewed as the tubes with elastic wall, whose elasticity could be slowly (during a minute) tuned to change its diameter thereby regulating regional blood supply. Recent findings showed that an artery is a much more sophisticated organ, which can change elasticity of vascular wall within a fraction of a second during a cardiac cycle due to activation of its smooth muscles manifested by generation of arterial action potentials. The rapid variations in elasticity of vascular wall resulted in three basic modes of arterial pulsing: passive, active, and intermediate. The latter is characterized by counteraction of dilation force of arterial pressure and the contractile one of smooth muscle in arterial wall, which can result in seemingly "rigid" artery of constant diameter. The prevalence of any of these forces results in active or passive pulsing modes. Existence of various pulsing modes raises the question of their effect on the main function of blood vessels, i.e., the transport of blood. The aim of this study is to assess the effect of various modes of arterial pulsing on hydraulic impedance of major arteries. The linearized Navier-Stokes equation was employed to develop a model of pulsatile flow of viscous incompressible fluid at small velocity via a conduit artery with the walls of variable or constant elasticity. An essential feature of the developed model is the shape of variable pressure drop applied to the ends of arterial segment, which simulates the real changes in arterial pressure during the heartbeat. Here, it is modeled by periodic (systolic) positive bell-shaped impulses with maxima corresponding to systolic arterial pressure, while the minimal plateau level refers to diastolic arterial pressure. The model assesses the changes in arterial hydraulic impedance during a cardiac cycle relatively to the stable level corresponding to constant blood flow driven by persistent pressure drop. Within intermediate variety of pulsing modes between the active and passive ones, the approximation of rigid arterial segment with infinite elasticity of arterial wall showed that hydraulic impedance in rigid artery is not constant due to inertial properties of the flowing blood. In passive pulsing mode characterized with constant elasticity of arterial wall, the diameter of artery changes in parallel with systolic pressure applied to the ends of arterial segment. At this, the overall change of hydraulic resistance is negative. In active pulsing mode, elasticity of arterial wall varies at different phase shifts relative to arterial pressure due to periodic contractions and relaxation of the smooth muscles in arterial wall. An important feature of active mode is possibility to decrease the hydraulic impedance during the front of arterial pressure. Various experimental modes of artery pulsing can be mathematically simulated. The passive and active modes of pulsing as well as a broad variety of intermediate pulsing modes with various phase shifts between arterial pressure and its diameter result in potency of the arteries to tune its performance in order to meet the regional circulatory requirements. The model showed that active arterial pulsing can diminish the arterial hydraulic impedance and contribute to the work needed for circulation thereby helping the pumping action of the heart.