Changes In Elastic Properties Research Articles

Effect of long-term testosterone replacement therapy on arterial stiffness and systemic endothelial function in male patients with hypogonadism

Abstract Purpose The study aims at providing the long-term effect of testosterone replacement therapy on systemic endothelial function, aortic stiffness and wave reflections in men with testosterone deficiency (TD). Methods This is a randomized single-center double-blind placebo-controlled trial involving 24 men (aged 51±9 years) with erectile dysfunction (ED) and total testosterone (TT) levels below 3.5 ng/ml randomised to receive either intramuscular (i.m) testosterone undecanoate (TU) injections (1000 mg as a single 4 mL i.m. injection at 0, 6, 18, 30 and 42 weeks) or an identical placebo at similar time points. A TU /placebo 2:1 randomization list was generated and patients were centrally assigned to one of the two arms, consecutively. Central blood pressure (BP), augmentation index (AIx), carotid-femoral pulse wave velocity (PWV) and brachial flow mediated dilatation (FMD) were measured at baseline, and at 18, 24, 30 and 44 weeks. Results The changes in central systolic BP and pulse pressure were more potent in the TU group compared to placebo group, however the decreases in these parameters were not statistically significant in point-of-time and time and group interaction. Repeated measures ANOVA revealed that the in point-of-time decrease in AIx was statistically significant in the group receiving TU (P=0.029) compared to men receiving placebo (figure). The maximal response in AIx was observed at 18 and 24 weeks (by 4.2% and 5.0%, respectively, all P<0.05). The interaction of time and group was also statistically significant (P=0.012) indicating significant differences between the treatment groups and time. PWV in the TU therapy group decreases during the whole study period, however the in point-of-time change was not statistically significant (P>0.05, figure). In men receiving TU the change in PWV was marginally significant only at 24 weeks (reduction by 0.34 m/s, P=0.05), whereas there were no significant differences in PWV between baseline and all other assessment time points. TU minimally increased brachial FMD up to 24 weeks (increase by 0.15%, P=0.05) from the beginning of therapy and the in point of the time change was not statistically significant (P>0.05, figure). Conclusion The 44-week TU i.m therapy was associated with a beneficial sustained effect on central AIx wave reflections thorough the whole study period. PWV decreased, particularly at 24 weeks, however the change in aortic elastic properties during the whole study session was not significant. Systemic endothelial function minimally improved compared to placebo. Given that AIx is an independent marker of cardiovascular disease and predictor of the corresponding risk, these findings have important implications to assess the effect of testosterone replacement interventions on cardiovascular performance and the corresponding risk of patients with ED and TD. Funding Acknowledgement Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Bayer Pharmaceuticals Figure 1. TU vs placebo Aix PWV and FMD changes

Integrating rock physics, PP-PS joint inversion and time-shifts to improve quantitative interpretation of time-lapse fluid and pressure changes

In this study, we show how to overcome the challenges of reliably estimating subtle 4D elastic property changes from seismic acquisitions just one year apart. We show that this is possible thanks to: 1) availability of highly repeatable seismic data and permanent reservoir monitoring (PRM); 2) the methodology for building 4D rock physics models that quantify 4D uncertainties related to seismic repeatability, 3) improving the quality of time-lapse estimates, especially at impedance S, due to the application of the 4D PP-PS joint inversion. This article summarizes the work of quantitative 4D interpretation by reporting how to build 4D rock physics models, how to estimate 4D elastic attributes (joint inversion of PP-PS data) and how the integrated interpretation of these results is performed. To validate the 4D interpretation, the results were compared to the production data from the injector and producer wells and to the outputs of the flow simulator. The integrated analysis shows how injection and production operations affect the reservoir properties, indicating preferred paths for water flow, the role of faults in reservoir hydraulic connectivity, regions where hydrocarbon production caused depletion, areas pressurized by water injection, and even the effect of the salinity contrast between the injection water and the brine. The application of this methodology allows updates to the simulation model that will affect future decisions.

Determination of models constants for thermomechanical properties of composites based on experimental data analysis

AnnotationThis article presents an algorithm for finding the constants in the model of changing the thermoelastic properties of polymer composites. The calculation of the constants is based on the processing of the experimentally obtained data. Optimization methods are applied to minimize the discrepancy between the experimental data and the analytical dependence on the constants that need to be found. Also, a method was proposed for determining the constants in the model of density change during destruction. The paper analyzes the effect of high temperatures on the change in density and elastic modulus of composite materials. On the basis of this, an algorithm was constructed for calculating the change in elastic properties up to temperatures of thermal destruction and during thermal destruction. The error between theoretical modeling and experimental data did not exceed 5%.

Origin of the Co-Seismic Variations of Elastic Properties in the Crust: Insight From the Laboratory.

Seismological observations highlighted that earthquakes are often followed by changes in elastic properties around the fault zone. Here, we studied the origin of these variations using stick‐slip experiments on saw‐cut granite samples presenting different degrees of bulk damage (i.e., microcracks). Stick‐slip events were induced under triaxial compression configuration with continuous active ultrasonic measurements at confining pressures representative of upper crustal conditions (15–120 MPa). Both the P‐wave velocity (VP) and amplitude (AP) showed drops, concurrently with stress drops, and had a non‐monotonic dependence toward the fault's stress state. Our experimental results suggest that co‐seismic changes in VP were mostly controlled by the elastic re‐opening of microcracks in the bulk, rather than by co‐seismic damage or the formation of fault gouge. Co‐seismic changes in AP were controlled by a combination of elastic re‐opening of microcracks in the bulk and inelastic processes (i.e., co‐seismic damage and gouge formation and dilation).

Modeling the processes of deformation and destruction of the rock sample during its extraction from great depths

Article investigates the change in the geophysical properties of rocks in the process of extracting the rock sample from great depths. Evaluation of changes in effective elastic properties, porosity and permeability of rock samples during extraction was carried out by means of finite element modeling. Assessment of the critical dimensions and orientation of internal defects, leading to the destruction of the rock samples during extraction from great depths, has been made based on the methods of linear destruction mechanics. Approach that makes it possible to calculate the change in the mechanical properties, porosity and fracturing of reservoir rocks in the process of extracting the rock sample from depths to the surface is proposed. Use of refined data on the mechanical properties of recoverable rock samples makes it possible to increase the accuracy of digital geological models required for geological exploration, determination of reservoir properties and oil and gas saturation of a field, and development of oil and gas deposits. Application of such models is especially relevant at all stages of the fields development with hard-to-recover reserves.

Classification of patients with Alzheimer\u2019s disease using the arterial pulse spectrum and a multilayer-perceptron analysis

Cerebrovascular atherosclerosis has been identified as a prominent pathological feature of Alzheimer’s disease (AD); the link between vessel pathology and AD risk may also extend to extracranial arteries. This study aimed to determine the effectiveness of using arterial pulse-wave measurements and multilayer perceptron (MLP) analysis in distinguishing between AD and control subjects. Radial blood pressure waveform (BPW) and finger photoplethysmography signals were measured noninvasively for 3 min in 87 AD patients and 74 control subjects. The 5-layer MLP algorithm employed evaluated the following 40 harmonic pulse indices: amplitude proportion and its coefficient of variation, and phase angle and its standard deviation. The BPW indices differed significantly between the AD patients (6247 pulses) and control subjects (6626 pulses). Significant intergroup differences were found between mild, moderate, and severe AD (defined by Mini-Mental-State-Examination scores). The hold-out test results indicated an accuracy of 82.86%, a specificity of 92.31%, and a 0.83 AUC of ROC curve when using the MLP-based classification between AD and Control. The identified differences can be partly attributed to AD-induced changes in vascular elastic properties. The present findings may be meaningful in facilitating the development of a noninvasive, rapid, inexpensive, and objective method for detecting and monitoring the AD status.

Mechanical stratigraphy in Mesozoic rocks of the San Juan Basin: Integration of stratigraphic and structural terms and concepts

We characterize relationships between stratigraphy and natural fractures in outcrops of Mesozoic strata that rim the San Juan Basin in New Mexico and Colorado. These outcrops expose fluvial and shallow-marine siliciclastic deposits and calcareous mudstones deposited in a distal marine setting. We focus primarily on a regionally extensive fracture set formed during the Eocene to minimize localized tectonic effects on fracture development. Where possible, we supplement our observations with wireline log- or laboratory-derived measurements of rock properties. Our goals are twofold: 1) to illustrate how direct integration of data and concepts from stratigraphy and structural geology can lead to better fracture characterization, and 2) to develop thought processes that will stimulate new exploration and development strategies. Genetic beds form one scale of stratification in the outcrops we describe. For example, sandstone beds can be arranged into coarsening and thickening upward successions that are the depositional record of shoreline progradation. In fluvial settings, cm- to dm-scale sandstone beds can also be part of m-scale single-storey channel complexes that, themselves, can be arranged into amalgamated channel complexes 10s of m thick. In these and other settings, it is important to distinguish between beds and features that can be defined via wireline logs because it is the former (cm- to dm-scale) that are usually the primary control the distribution of natural fractures. The extension fractures we describe are typically bed-bound, with bedding being defined by lithology contrasts and the associated changes in elastic properties. Fracture spacing distributions are typically lognormal with average spacing being less than bed thickness. Although mechanical bedding and depositional bedding are commonly the same, diagenesis can cut across bed boundaries and complicate this relationship, especially where lithologic contrasts are small. Deposits from similar depositional environments which undergo different diagenetic histories can have substantially different mechanical properties and therefore deform differently in response to similar imposed stresses.

Coupled Brittle and Viscous Micromechanisms Produce Semibrittle Flow, Grain‐Boundary Sliding, and Anelasticity in Salt‐Rock

AbstractThe operation of fracture, diffusion, and intracrystalline‐plastic micromechanisms during semibrittle deformation of rock is directly relevant to understanding mechanical behavior across the brittle‐plastic transition in the crust. An outstanding question is whether (1) the micromechanisms of semibrittle flow can be considered to operate independently, as represented in typical crustal strength profiles across the brittle to plastic transition, or (2) the micromechanisms are coupled such that the transition is represented by a distinct rheology with dependency on effective pressure, temperature, and strain rate. We employ triaxial stress‐cycling experiments to investigate elastic‐plastic and viscoelastic behaviors during semibrittle flow in two distinctly different monomineralic, polycrystalline, synthetic salt‐rocks. During semibrittle flow at high differential stress, granular, low‐porosity, work‐hardened salt‐rocks deform predominantly by grain‐boundary sliding and wing‐crack opening accompanied by minor intragranular dislocation glide. In contrast, fully annealed, near‐zero porosity salt‐rocks flow at lower differential stress by intragranular dislocation glide accompanied by grain‐boundary sliding and opening. Grain‐boundary sliding is frictional during semibrittle flow at higher strain rates, but the associated dispersal of water from fluid inclusions along boundaries can activate fluid‐assisted diffusional sliding at lower strain rates. Changes in elastic properties with semibrittle flow largely reflect activation of sliding along closed grain boundaries. Observed microstructures, pronounced hysteresis and anelasticity during cyclic stressing after semibrittle flow, and stress relaxation behaviors indicate coupled operation of micromechanisms leading to a distinct rheology (hypothesis 2 above).

Non-linear ultrasonic and viscoelastic properties of gelatine investigated in the temperature range of 30 °C–60 °C

Analysis based on the determination of the multifactorial non-linearity parameter (β) is a promising non-destructive investigation and testing technique. The contribution of temperature variations on the non-linear coefficient is known to be lower than that of hydrostatic pressure changes. We investigated the effect of temperature on the non-linearity parameter in the range 30 °C–60 °C for a viscous, gelatinous compound, resulting from controlled hydrolysis of the collagen protein. Considerable thermal effects are realized and are related to changes in viscous and elastic properties. Remarkable changes in the non-linearity coefficient at temperatures corresponding to the transition temperature of gelatine of 60 °C indicate a signature while no outspoken hysteresis effects were realized with cyclic temperature sweeps. Despite the non-Newtonian nature of the gel, our experiments show comparability to water within the examined range of temperature, which corresponds to a wavelength shift of about 40 μm.

Effects of Elevated Temperatures on the Microstructural, Physico-Mechanical and Elastic Properties of Barakar Sandstone: A Study from One of the World’s Largest Underground Coalmine Fire Region, Jharia, India

Experimental investigations of the effects of elevated temperature on microstructural, mineralogical, physico-mechanical and elastic properties of rocks were carried out to understand the effect of underground coal fire along with thermal damage and failure initiation in Barakar sandstone from the Jharia coalfield, India. Discolouration analysis, petrographic studies, scanning electron microscopy, thermogravimetry, differential thermal analysis and electron probe micro analysis were carried out to understand the microstructural and mineralogical changes in thermally treated samples. The experimental results suggest that the changes in investigated properties follow three characteristic thermal zones: zone I (25–300 °C), zone II (300–500 °C) and zone III (500–800 °C). Among all, zone II is a prominent transition region where a rapid increase in crack density, porosity and thermal damage is observed along with a sharp reduction in seismic wave velocities, uniaxial compressive strength, tensile strength and elastic parameters. Development of thermal stress-induced intergranular and intragranular micro-cracks, evaporation of organic matters, and dehydration and thermal decomposition of minerals are the most conspicuous reasons for the observed changes in this zone. Zone III is characterized by phase transformation of quartz, recrystallization and partial melting of cement and phyllosilicates that filled some of the existing micro-cracks, resulting in a local change of porosity, strength and elastic properties. Developments of different failure modes are observed in different temperature ranges such as simple shear along a single plane in zone I, progressive growth of Y-shaped (double plane) shearing in the zones II and III (400–700 °C) and axial splitting at 800 °C. The results from this study provide comprehensive elaboration of thermal effects on sandstones at a particular temperature range.

Diagnostics of Metals’ Plastic Deformation in Terms of Elastic Properties

Nondestructive monitoring of the plastic deformation of metal after machining is proposed, on the basis of the change in elastic properties of the material.

Комбінування детермінованого та стохастичного методів до розв’язання задачі дефектоскопії пружного стрижня

The paper considers the problem of natural harmonic oscillations of an elastic rod with stress-free ends in the presence of one or a set of defects. Defects are modeled by the inhomogeneity of the Young's modulus. The location of the defects, their geometric size, which is considered small, and the change in elastic properties are the parameters of the defects. The analysis of natural frequency shifts caused by the defect of the rod is the subject of the study. The aim of the work is a mathematical substantiation for the construction of fast and stable algorithms for determining the defect parameters of elastic bodies by analyzing free oscillations. The paper uses and compares fundamentally different research methods. The first methods are classical mathematical methods of mechanics, applied to the analysis of deterministic systems and based on analytical studies combined with numerical implementation. In contrast, a composite machine learning meta-algorithm used in standard statistical classification and regression - Bootstrap-aggregated Regression Trees (BART) - is used to solve the inverse problem. When comparing the constructed algorithms, the statistical method Sampling was used, which allowed to quantify the accuracy and stability of the algorithms.

The control of the condition of the stainless steel under cyclic loading by acoustic and eddy current method

This paper presents the results of ultrasonic and eddy-current measurements of the characteristics of austenitic stainless steel AISI 321 under fatigue failure. The effect of the strain amplitude on the intensity of changes in elastic and magnetic properties is studied. The use of a combination of eddy current and ultrasonic measurements makes it possible to assess the state of steel AISI 321 under fatigue failure is shown. The technique for measuring ultrasonic parameters described in this paper allows us to register changes in the structural state of a material under fatigue failure long before the crack is formed. The eddy current method is used to determine the volume fraction of martensite with ferromagnetic properties. An algorithm is proposed for estimating the number of loading cycles and the operating time of metastable austenitic steel AISI 321 based on the data of ultrasonic and eddy current measurements.

Comparing different approaches of time-lapse seismic inversion

Abstract Time-lapse (4D) seismic inversion aims to predict changes in elastic rock properties, such as acoustic impedance, from measured seismic amplitude variations due to hydrocarbon production. Possible approaches for 4D seismic inversion include two classes of method: sequential independent 3D inversions and joint inversion of 4D seismic differences. We compare the standard deterministic methods, such as coloured and model-based inversions, and the probabilistic inversion techniques based on a Bayesian approach. The goal is to compare the sequential independent 3D seismic inversions and the joint 4D inversion using the same type of algorithm (Bayesian method) and to benchmark the results to commonly applied algorithms in time-lapse studies. The model property of interest is the ratio of the acoustic impedances, estimated for the monitor, and base surveys at each location in the model. We apply the methods to a synthetic dataset generated based on the Namorado field (offshore southeast Brazil). Using this controlled dataset, we can evaluate properly the results as the true solution is known. The results show that the Bayesian 4D joint inversion, based on the amplitude difference between seismic surveys, provides more accurate results than sequential independent 3D inversion approaches, and these results are consistent with deterministic methods. The Bayesian 4D joint inversion is relatively easy to apply and provides a confidence interval of the predictions.

The quartz α↔β phase transition: Does it drive damage and reaction in continental crust?

The α↔β phase transition in quartz is accompanied by relatively large, anisotropic changes in cell volume and elastic stiffness properties. Because quartz is among the most abundant minerals in Earth's continental crust, these changes have the potential to profoundly influence the state of stress, mechanical properties, metamorphism, and rheology of crustal rocks. Laboratory experiments confirm strongly enhanced microcracking as rocks cross the transition. In addition, limited seismological studies suggest that the α↔β transition may cause extensive microcracking in the crust. However, the micromechanical basis for potential transition-induced damage has not been quantitatively explored. Here we use numerical methods to show that elastic stresses arising from the transition can greatly exceed the brittle tensile and shear strengths of common crustal rocks and minerals at various confining pressures. In particular, we show that contraction during the down-temperature β→α transition is far more effective than expansion during the up-temperature α→β transition at promoting possible brittle failure and/or recrystallization (damage). Our results suggest that the α↔β transition may play an important role in damaging the continental crust, particularly in rock volumes that experience geologically rapid changes in temperature or pressure. In these environments, the transition may weaken rocks, establish transient permeability, facilitate advective mass transport and metamorphic reactions, and potentially nucleate earthquakes.

Elastic softening of sandstone due to a wideband acoustic pulse observed by dynamic acousto-elastic testing

Laboratory measurements of finite-amplitude, wideband elastic pulse propagation in a thin bar of Texas moss sandstone have been reported [Muir et al., JASA 147 (2020)] that utilized pulses generated by impact excitation with a pendulum hammer at one end of the bar. Each pulse is essentially unipolar in strain, with bandwidth of approximately 3 kHz and amplitude between 10 and 130 microstrain. Reduction of the sandstone elastic modulus by up to 17% resulted from propagation of the impact-generated pulse, as calculated from time-of-flight measurements of the pulse as it reflected between the ends of the bar. In the present work, elastic softening is observed locally using a Dynamic Acousto-Elastic Testing (DAET) configuration. During propagation of an impact-generated pulse, changes in the sandstone elastic properties are observed by tracking variations in the arrival time and amplitude of a continuous-wave 1 MHz P-wave signal that propagates perpendicular to the bar axis. Repetitive reflection of the pulse from the stress-free ends of the bar enables separate observation of effects from compressive and tensile strains. Reduction of the elastic modulus of up to 20% is observed, with almost all of the softening occurring during the tensile phase of the impact-generated pulse. a)Deceased.

Introduction of lung ultrasound surface wave elastography

Ultrasonography is not widely used for lung assessment because ultrasound cannot image deep lung tissue. Many lung diseases including interstitial lung disease (ILD) are associated with changes in lung's elastic properties. ILD includes multiple serious lung disorders associated with lung fibrosis and can lead to respiratory failure and pulmonary hypertension. High-resolution CT (HRCT) is the clinical standard for diagnosing lung fibrosis, but it results in increased radiation exposure for patients. Lung fibrosis is associated with stiffened lung parenchyma. Current clinical techniques including HRCT cannot measure lung elastic properties. Most ILDs are typically distributed in the lung's peripheral and subpleural regions. We developed noninvasive lung ultrasound surface wave elastography (LUSWE) to measure lung surface wave speed safely and quickly. In this abstract, we will present some basics for LUSWE. We will also present its clinic application for assessing ILD. We studied 30 healthy controls, 16 mild ILD patients, 45 moderate ILD patients, and 27 severe ILD patients. Lung surface wave speed has good sensitivity and specificity for separating ILD patients from healthy subjects as well as for separating mild ILD patients from healthy subjects. LUSWE is useful for other lung disorders such as pulmonary edema.

Morin-type transition in 5C pyrrhotite

Abstract We report the discovery of a low-temperature spin-flop transition in 5C pyrrhotite at ~155 K that is similar to those seen in hematite at 260 K and FeS (troilite) at 440 K. The 5C crystal was produced by annealing a 4C pyrrhotite crystal at 875 K to produce a change in the vacancy-ordering scheme that developed during cooling. The 5C structure is confirmed by single-crystal X-ray diffraction and the stoichiometry and homogeneity by electron microprobe and SEM BSE mapping. Resonant ultrasound spectroscopy (RUS), heat capacity, and magnetization measurements from room temperature down to 2 K are reported. The transition is marked by a steep change in elastic properties at the transition temperature, a peak in the heat capacity, and weak anomalies in measurements of magnetization. Magnetic hysteresis loops and comparison with the magnetic properties of 4C pyrrhotite suggest that the transition involves a change in orientation of moments between two different antiferromagnetic structures, perpendicular to the crystallographic c-axis at high temperatures and parallel to the crystal-lographic c-axis at low temperatures. The proposed structures are consistent with a group theoretical treatment that also predicts a first-order transition between the magnetic structures.

Elastic properties as indicators of heat flux into cold near-surface Arctic sediments

Temperatures in the terrestrial Arctic today are increasing at the highest rate on earth, and heat flux into the cold sediments may result in extensive thawing. Thawing sediments lose their mechanical strength; therefore, warming has significant geomorphic consequences. We have combined heat flux, rock physics, and seismic modeling to estimate the change in elastic properties related to various published future climate scenarios in the Arctic, and we thus investigate the feasibility of exposing thawing rates from seismic data. The heat-flux model was validated using temperature data continuously recorded at the surface and within a well in Adventdalen, Svalbard. We estimated the evolving temperatures in an upper vertical section of the well using the heat-flux model, and we compared them with actual measured well temperatures. The modeled and measured data were consistent, even though our simplified model ignores heat transport due to fluid flow and the effects of clay. The heat-flux modeling resulted in subsurface isotherms that were input to rock-physics modeling based on two-end-member mixing of fully frozen and unfrozen composites to delineate possible climate effects on the seismic properties of the sediments. The results show that the elastic and seismic properties of (partly) frozen unconsolidated near-surface saline sediments strongly depend on heat flux into the subsurface, and they vary seasonally and between different climate scenarios. Seismic data obtained by full-waveform modeling and real experiments in Adventdalen show that time-lapse analysis of Rayleigh waves may be an efficient tool for monitoring heat flux into the terrestrial Arctic.

Relaxation behavior of densified sodium aluminoborate glass

In this work, we study the relaxation behavior of a densified sodium aluminoborate glass by means of coupled Raman spectroscopy, Brillouin spectroscopy, and differential scanning calorimetry analyses. First, we show that the changes in elastic properties upon densification are largely associated with structural modifications in the glass network at short- and medium-range orders. Then, the evolution of the structural and elastic properties of the densified glass has been monitored in situ in the coupled DSC-Brillouin-Raman setup during isothermal annealing at different temperatures below the glass transition temperature. The stretched exponential function is found to well describe the observed relaxation kinetics, however, the stretching factor β varies non-monotonically with temperature. In contrast, the Arrhenius behavior of the characteristic decay times is deduced by lifetime distribution analysis, revealing three different relaxation processes with typical activation energies of 170±25, 200±5, and 280±15 kJ/mol. The relative contributions of these processes to the overall relaxation kinetics are found to vary with the temperature as well as the type of parameter considered (structural, elastic, or thermal), and hence, the relaxation kinetics cannot be properly understood using the stretched exponent function. The possible origins of the different relaxation processes are discussed.