Contribution of Stress Testing to the Management of Ischemic Heart Disease in Mali

Introduction: Exercise stress testing (on a treadmill or ergometer bicycle) is an important test in cardiology for diagnosing myocardial ischemia. This test in Mali is still in its beginning compared to other countries in the sub-region. The lack of data in Mali prompted this study, which aimed to evaluate the indications of this activity and its diagnostic contribution to cardiology in Mali. Materials and Methods: This was a retrospective, descriptive study. The study was conducted at the “TOUCAM” medical clinic in Kati based on the analysis of stress test reports between January 2016 and August 2022. Result: During the study period, we documented 73 patients who underwent exercise testing on a bicycle ergometer for suspected coronary heart disease. The mean age of our patients was 47.5 ± 13.8 years (14 and 79 years). Males accounted for the majority (78.1%). The sex ratio is 3.5. More than half of our patients were overweight or obese (77.1%). Hypertension and diabetes affected 52.1% and 25.8% of patients, respectively. 20.8% of patients had coronary artery disease. renin-angiotensin-aldosterone system blockers (56.8%) and beta-blockers (51.3%). The main indications were chest pain (63.0%) and ischemia detection (15.1%). A modified STEEP protocol was used. The majority of our patients (71.2%) achieved at least 85% of their maximum theoretical heart rate. The main reason for the termination of the study was fatigue (57.3%). The average duration was 11.3 ± 4.2 minutes. 24.7% thought the stress tests were positive and 17.8% thought they were controversial. Conclusion: This study demonstrates the importance of stress testing in the diagnosis and treatment of ischemic heart disease, especially in settings where we have very limited access to coronary angiography.

Stress test and analysis based on SMS fiber structure with high sensitivity

Single mode-multimode-single mode （SMS） sensor is widely used for parameters measurement, such as bending, dis-placement, temperature, strain, refractive index, etc. Generally, SMS sensor has advantages of simple structure, low cost and easy layout, therefore it has become a research hotspot in recent years. In this paper, the multimode fiber with large core is used for manufacturing SMS structure with high sensitivity. Firstly, the multimode fiber with core/cladding diameters of 105/ 125 jitm has access to the system by means of single mode optical fiber. Secondly, SMS device structure is manufactured by welding the eccentric shaft of multimode optical fiber. Afterwards, mode interference effect and spectral response characteristics of the structure of single mode-multimode-single mode optical fiber are analyzed theoretically. Finally, with the help of a wide spectrum light source and a spectrum analyzer, the transmission spectra characteristics of SMS optical fiber with strain is tested. By observing the curve that the wave changes with stress, the sensitivity is calculated and it is consistent with theoretical value .

Nondestructive Testing and Characterization of Residual Stress Field Using an Ultrasonic Method

To address the difficulty in testing and calibrating the stress gradient in the depth direction of mechanical components, a new technology of nondestructive testing and characterization of the residual stress gradient field by ultrasonic method is proposed based on acoustoelasticity theory. By carrying out theoretical analysis, the sensitivity coefficients of different types of ultrasonic are obtained by taking the low carbon steel（12%C） as a research object. By fixing the interval distance between sending and receiving transducers, the mathematical expressions of the change of stress and the variation of time are established. To design one sending-one receiving and oblique incidence ultrasonic detection probes, according to Snell law, the critically refracted longitudinal wave（LCR wave） is excited at a certain depth of the fixed distance of the tested components. Then, the relationship between the depth of LCR wave detection and the center frequency of the probe in Q235 steel is obtained through experimental study. To detect the stress gradient in the depth direction, a stress gradient LCR wave detection model is established, through which the stress gradient formula is derived by the relationship between center frequency and detecting depth. A C-shaped stress specimen of Q235 steel is designed to conduct stress loading tests, and the stress is measured with the five group probes at different center frequencies. The accuracy of ultrasonic testing is verified by X-ray stress analyzer. The stress value of each specific depth is calculated using the stress gradient formula. Accordingly, the ultrasonic characterization of residual stress field is realized. Characterization results show that the stress gradient distribution is consistent with the simulation in ANSYS. The new technology can be widely applied in the detection of the residual stress gradient field caused by mechanical processing, such as welding and shot peening.

Shortness of breath in clinical practice: A case for left atrial function and exercise stress testing for a comprehensive diastolic heart failure workup

The symptom cluster of shortness of breath(SOB) contributes significantly to the outpatient workload of cardiology services. The workup of these patients includes blood chemistry and biomarkers, imaging and functional testing of the heart and lungs. A diagnosis of diastolic heart failure is inferred through the exclusion of systolic abnormalities, a normal pulmonary function test and normal hemoglobin, coupled with diastolic abnormalities on echocardiography. Differentiating confounders such as obesity or deconditioning in a patient with diastolic abnormalities is difficult. While the most recent guidelines provide more avenues for diagnosis, such as incorporating the left atrial size, little emphasis is given to understanding left atrial function, which contributes to at least 25% of diastolic left ventricular filling; additionally, exercise stress testing to elicit symptoms and test the dynamics of diastolic parameters, especially when access to the "gold standard" invasive tests is lacking, presents clinical translational gaps. It is thus important in diastolic heart failure work up to understand left atrial mechanics and the role of exercise testing to build a comprehensive argument for the diagnosis of diastolic heart failure in a patient presenting with SOB.

Research on magnetic testing method of stress distribution

For implementing nondestructive evaluation of stress distribution inside ferromagnetic material, a magnetic testing method was developed which does not need artificial magnetizing field. This method was implemented by testing the normal component of the magnetic flux leakage above the object being tested with a constant lift off from 1 to 10?mm. The distribution of the stress inside the specimen can be gotten from that of the normal component of the magnetic flux leakage. A stress concentration specimen, which is a 10?mm thickness mild steel plate with a welding seam on it, was tested using this method. The stress distribution of the magnetic testing was identical with that of small hole stress testing method. It indicates that the stress distribution of ferromagnetic material can be known by the magnetic testing method.

Mechanical properties of high-strength concrete subjected to high temperature by stressed test

Recently, the effects of high temperature on compressive strength and elastic modulus of high strength concrete were experimentally investigated. The present study is aimed to study the effect of elevated temperatures ranging from 20 ℃ to 700 ℃ on the material mechanical properties of high-strength concrete of 40, 60 and 80 MPa grade. During the strength test, the specimens are subjected to a 25% of ultimate compressive strength at room temperature and sustained during heating, and when the target temperature is reached, the specimens are loaded to failure. The tests were conducted at various temperatures (20-700 ℃) for concretes made with W/B ratios of 46%, 32% and 25%, respectively. The results show that the relative values of compressive strength and elastic modulus decrease with increasing compressive strength grade of specimen.

Optimal Design of Multiple Stresses Accelerated Life Test Plan Based on Transforming the Multiple Stresses to Single Stress

For planning optimum multiple stresses accelerated life test plans, a commonly followed guiding principle is that all parameters of the life-stress relationship should be estimated, and the number of the stress level combinations must be no less than the number of parameters of the life-stress relationship. However, the general objective of an accelerated life test（ALT） is to assess thep-th quantile of the product life distribution under normal stress. For this objective,estimating all model parameters is not necessary, and this will increase the cost of test. Based on the theoretical conclusion that the stress level combinations of the optimum multiple stresses ALT plan locate on a straight line through the origin of coordinate, it is proposed that a design idea of planning the optimum multiple stresses ALT plan through transforming the problem of designing an optimum multiple stresses ALT plan to designing an optimum single stress ALT plan. Moreover, a method of planning the optimum multiple stresses ALT plan which can avoid estimating all model parameters is established. An example shows that, the proposed plan which only has two stress level combinations could achieve an accuracy no less than the traditional plan, and save the test time and cost on one stress level combination at least; when the actual product life is less than the design value, even the deviation of the model initial parameters value is up to 20%, the variance of the estimation of thep-th quantile of the proposed plan is still smaller than the traditional plans approximately 25%. A design method is provided for planning the optimum multiple stresses ALT which uses the statistical optimum degenerate test plan as the optimum multiple stresses accelerated life test plan.

Methodology to Evaluate Fatigue Damage of High-Speed Train Welded Bogie Frames Based on On-Track Dynamic Stress Test Data

The current method of estimating the fatigue life of railway structures is to calculating the equivalent stress amplitude based on the measured stress data. However, the random of the measured data is not considered. In this paper, a new method was established to compute the equivalent stress amplitude to evaluate the fatigue damage based on the measurable randomness, since the equivalent stress is the key parameter for assessment of structure fatigue life and load derivation. The equivalent stress amplitude of a high-speed train welded bogie frame was found to obey normal distribution under uniform operation route that verified by on-track dynamic stress data, and the proposed model is, in effect, an improved version of the mathematical model used to calculate the equivalent stress amplitude. The data of a long-term, on-track dynamic stress test program was analyzed to find that the normal distribution parameters of equivalent stress amplitude values differ across different operation route. Thus, the fatigue damage of the high-speed train welded bogie frame can be evaluated by the proposed method if the running schedule of the train is known a priori. The results also showed that the equivalent stress amplitude of the region connected to the power system is more random than in other regions of the bogie frame.

Acoustic cardiography to improve detection of coronary artery disease with stress testing

AIM:To assess if performance of 12-lead exercise tolerance testing(ETT) can be improved by simultaneous acoustic cardiography and to compare the diagnostic performances of electrocardiography(ECG) during ETT and acoustic cardiography for detection or exclusion of angiographically proven coronary artery disease(CAD).METHODS:We conducted an explorative study with retrospective data analysis using a convenience sample of consecutive patients(n = 59,mean age:62 years) from an outpatient clinic in Switzerland,who were referred for ETT by their general practitioner on suspicion of CAD,and in whom,coronary angiography was carried out.Measurements included sensitivity,specificity,likelihood ratios and receiver operating characteristic curves.A standard,symptom-limited,12-lead ECG exercise tolerance test was performed by independent persons with simultaneous acoustic cardiography and subsequent cardiac angiography for determination of significant CAD.RESULTS:Thirty-four of the 59 adult subjects(58%) had a final diagnosis of CAD by angiography,and in 25 subjects,CAD was excluded by angiography.Sensitivity/specificity of ST segment depression in the group was 29%/92%,whereas the most powerful acoustic cardiographic parameter was the strength of the fourth heart sound(S4),with corresponding sensitivity/specificity of 53%/92%.The disjunctive combination of the S4 and ST depression had sensitivity/specificity of 68%/84%.CONCLUSION:In this preliminary pilot study,the use of acoustic cardiography alone during ETT or disjunctively with ST depression has been shown to be a simple and convenient method for the detection of CAD,which was superior to ST depression on the standardized ECG.

A recoverable stress testing algorithm for compression and encryption cards

This study proposes a recoverable stress testing algorithm （RSTA） for such special devices as compression/decompression card and encryption/deeryption card. It uses a chaos function to generate a random sequence, and then, according to the random sequence, generates an effective command sequence. The dispatch of command obeys a special schedule strategy we designed for such devices, i.e., the commands are sent according to the command sequence, and the complete commands are put in a buffer for further result check. RSTA is used to test the HIFN compression acceleration card SAICHI-1000. Test results show that RSTA can make the card work continuously and adequately.

SYNTHETIC STRESSLIFE TESTING OF MECHATRONIC PRODUCTS UNDER VARIABLE STRESS SPECTRUM

Mechatronic products usually endure the variable stress spectrum when they operate in certain operational condition and environmental condition, which obey the Weibull distribution. In accordance with the features of mechatronic product, this paper analyzes the failure mode, its corresponding sensitive stress and the design principles of life testing profiles. Based on the above analyses, this paper presents a synthetic stress life testing method based on the hybrid Weibull distribution and its statistical method under variable stress spectrum to evaluate the reliability and life indices of mechatronic products. Because the mechatronic products have many characteristics such as high price, long life and small testing samples, the synthetic stress life testing method under variable load spectrum can simulate the real various spectra, decrease the life testing time and reduce the testing samples. So it is effective to carry out the life testing to mechatronic products. The application results of hydraulic pumps indicate that this method can easily handle the experimental data under variable amplitude spectrum, obtain the high precision parameters point estimation and confidence interval estimation and reduce the testing cost greatly.

Preoperative nuclear stress testing in the very old patient population

BACKGROUND Elderly patients awaiting moderate to high-risk surgery may undergo nuclear stress testing(NST)in order to evaluate their cardiovascular risk.The prognostic utility of such testing in the very elderly(≥85 years)has yet to be fully evaluated.Octogenarians and nonogenarians frequently have a number of concurrent conditions including a high rate of coronary disease,and therefore the prognostic value of NST for their preoperative risk assessment has been questioned.Our evaluation assesses the ability of nuclear stress testing to predict peri-operative cardiac outcomes in this patient population.AIM To investigate the ability of NST to predict peri-operative cardiac outcomes in elderly patients awaiting moderate to high-risk surgery.METHODS Patients≥85 years undergoing pre-operative NST were retrospectively evaluated.Patients undergoing low-risk surgery were excluded.Major adverse cardiac events(MACE)were considered any adverse event that occurred prior to discharge and included acute heart failure,arrhythmia,acute myocardial infarction,unstable angina,or death.Associations between patient risk factors,MACE,and the obtained results of the pre-operative stress testing,ejection fraction(<40%or≥40%),summed stress score(≤8,≥9),and the summed difference score(≤0,>0)were analyzed.RESULTS A total of 69 patients(mean age 88±2.6 years,31 males)underwent nuclear stress testing prior to surgery.There were 41(60%)patients found to have an abnormal NST.Sixteen(23%)patients were noted to experience post-operative MACE.No significant associations between risk factors and MACE were noted.Patients with an abnormal NST and/or a summed stress score≥9 weresignificantly(P<0.01)more likely to develop peri-operative MACE.CONCLUSION Indicated preoperative NST is useful to assess pre-operative risk in elderly patients≥85 years undergoing moderate to high-risk surgery.

Use of Plastic Correction Formula to Improve Accuracy of Welding Residual Stress Test with Blind-Hole Method

The blind-hole method is the most widely used approach to experimentally determine the distribution of residual stress. This paper aims to improve test accuracy of welding residual stress and conducts an experimental study on the strain release factors involved when using the blind-hole method for Q235 and Q345, two steels commonly used in building structures. The ranges of strain release factors A and B in the elastic stage, the effects of strain release factors on residual stress calculated values, and the plastic corrected strain release factors are analyzed considering of the effect of plastic deformation around the blind hole on measurement accuracy. Finally, a simplified calculation formula to determine strain release factors is proposed for use with the blind-hole method. Results show that in the elastic stage, strain release factor A for Q235 and Q345 ranges from-0.399 to-0.525 and strain release factor B from-0.791 to-0.960. Changing the strain release factors A and B shows that calculated residual tensile stress varies in relation to a decrease in both factor values. However, there is a increase in calculated residual compressive stress with a decrease in the strain release factor A value, but there is an decrease with a decrease in strain release factor B value. Calculated residual stress applied to elastic strain release factors is compared with that applied to amended plastic strain release factors for Q235 steel. The maximum deviation between calculated residual stress and test stress is reduced from 21.1 to 1.0%,and for Q345 steel from 26.5 to 1.2%. It is thus evident that the plastic correction formula proposed in this paper can be used in calculations when conducting a residual stress test.

Research on Stress Testing of OSPF Protocol Implementation

The stability and robustness of routing protocol implementations (RPI) in a router are becoming more and more important with the growth of Internet scale. A novel approach named stress testing is proposed to test the properties of RPI. Compared with some traditional test techniques, stress testing is remarkably necessary to inspect and analyze RPI. The test environment is proposed and the test process of OSPF RPI is illustrated by a stochastic Petri Net model with large-scale route simulation and OSPF protocol emulation. Based on this model, the integrated performance tester (IP-TEST) is designed and developed, with which we test a CISCO2600 router. With mathematical methods, we find that the computational complexity of OSPF implementation in this router is O((lnN) 4)to the number of its routing table entries. This experiment shows that this technique can inspect the stability, the computational complexity and the scalability of RPI. Furthermore, it can also be widely used with other routing protocols, such as RIP and BGP.

The Extension Rate of the Medial Collateral Ligament of the Knee Joint during the Valgus Stress Test: Two Case Reports

This study aimed to evaluate the influence of measuring the length of the medial collateral ligament (MCL) to compare the MCL burden when the knee joint is placed under valgus stress in the open and closed and closed kinetic chain. Two examiners conducted the examination. The MCL length was measured using ultrasonography. Two subjects were measured in unload bearing and load-bearing positions, with and without valgus stress test at the knee joint extension and 30° flexion, under eight different measurement conditions. The MCL of the subject was delineated in the longitudinal direction using an ultrasound system. The attachment points of the medial femoral and tibial condyle of the MCL were identified, and the ligament length was measured. The MCL rate before and after the valgus stress test in the loading and unloading positions was calculated. The MCL length increased by an average of 8.9% when the external stress test was performed in the non-weight bearing and knee extension positions and by an average of 17.0% when external stress was applied in the non-weight bearing and knee flexion positions. The MCL length increased by an average of 12.2% when the external stress test was performed in the load-bearing and knee extension positions and an average of 8.9% when the valgus stress test was applied in load-bearing and knee flexion positions. In conclusion, the effect of valgus stress on the MCL differs between load-bearing and non-load-bearing positions. It is considered that the dynamic stabilization mechanism works in the knee joint flexion position in the load position and works simultaneously as the static stabilization mechanism, which limits the knee joint valgus and reduces the extension rate of MCL. Therefore, this study reconsiders the shifting of traditional therapy from open kinetic chain to close kinetic chain.

Autonomic Function in Individuals with Slow Heart Rate Response following an Exercise Stress Test

Objective: To examine the autonomic function using HRV measures in apparently healthy individuals undergoing exercise stress test (EST) and demonstrating slow HRR response. Methods: HRV was measured with 12 lead ECGs during graded EST and analyzed via a post-processing method. Autonomic function was determined by Power Spectral Analysis of the very low frequency (VLF), low frequency (LF), high frequency (HF), and the ratio of LF/HF. We correlated HRV indices with resting, exercise, and recovery data. Results: No differences were found in anthropometric measurements, peak EST HR, and METS between individuals with slow HRR (below 18 b/min) compared with controls (HRR > 18 b/min). Only the VLF component of the HRV indices was statistically different (p = 0.03) at one-minute post-exercise compared with controls. Additionally, a significant correlation between HRR and resting LF and HF indices was found in the individuals with slow HRR but not in the controls. Conclusion: In apparently healthy individuals with slow HRR post-EST, autonomic function did not demonstrate any differences at any phase of the EST, including at one minute of recovery. However, a significant correlation was found between resting LF and HF powers and HRR in individuals with slow vagal reactivation post-exercise. The clinical and prognostic implications of such observation deserve further investigation.

Global test of seismic static stress triggering model

Seismic static stress triggering model is tested using Harvard centroid moment tensor (CMT) solution catalogue of 1976~2000 and concept of earthquake doublet. Result shows that seismic static stress triggering effect does exist in the view of global earthquakes, but the effect is very weak. Dividing the earthquakes into thrust focal mechanism, normal focal mechanism, strike-slip focal mechanism, we find that non-strike-slip focal mechanism earthquakes have significant triggering effect, whereas, the triggering effect in strike-slip focal mechanism earthquakes is not obvious. Divided the subsequent events delay time of earthquake doublet into 5 classes of t1, t<1, t10, t<10, 1t10 (t is in unit of d), then seismic static stress triggering effect does not change with delay time in short time period after earthquakes. The research on seismic static stress triggering in different regions of the world indicates that triggering effect is significant in subduction belts. Seismic static stress triggering model is tested by using earthquake doublets in China and its adjacent region. The result indicates that seismic static stress triggering effect cannot be observed easily in China and its adjacent region due to the seismic focal mechanism type (most of the earthquakes are strike-slip earthquakes).

Detonator stepping stress acceleration life test

Through the failure mechanism analysi s and simulation test of a certain kind of detonator,this paper confirms the str ess level of the stepping stress acceleration life test of the detonator,and t hen e stablishes the data processing mathematical model and storage life forecasting m ethod.At last,according to the result of the stepping stress acceleration lif e test of the detonator,this paper forecasts the reliable storage life of the detonator under the normal stress level.

Impact of elliptical boreholes on in situ stress estimation from leak-off test data

We developed an inversion technique to determine in situ stresses for elliptical boreholes of arbitrary trajectory. In this approach, borehole geometry, drilling-induced fracture information, and other available leak-off test data were used to construct a mathematical model, which was in turn applied to finding the inverse of an overdetermined system of equations.The method has been demonstrated by a case study in the Appalachian Basin, USA. The calculated horizontal stresses are in reasonable agreement with the reported regional stress study of the area, although there are no field measurement data of the studied well for direct calibration. The results also indicate that 2% of axis difference in the elliptical borehole geometry can cause a 5% difference in minimum horizontal stress calculation and a 10% difference in maximum horizontal stress calculation.