Precursor Of Failure Research Articles

Deep and confident prediction for a laboratory earthquake

Many laboratory fault failure experiments are conducted as analogue of earthquakes, in which most of them are coupled with acoustic emission (AE) as a powerful diagnostic tool for investigating failure precursors. The purpose of this study is to predict time to the next failure in a laboratory fault failure experiment before failures happen based on the instantaneous recorded AE signals. A customized deep learning network comprising the convolutional neural network module and the recurrent neural network module is built and trained using raw AE data directly. No statistical characteristics or handmade features are extracted from raw data, avoiding any possible precursor information losses. More than 600 million AE data from a repetitive fault failure experiment are segmented as several thousand equilong sequences to form training and validation samples. The proposed network delivers satisfactory predicted results with the R2 value 0.55, much better than results using traditional earthquake catalogs method. Results of this study also demonstrate that our network does not prioritize those AE signals collected when failures impend, which is a common bias in traditional earthquake prediction methods. This study definitely holds the promise of using deep learning in earthquake prediction. Further studies are needed when analogous studies proceed to an industrial practice.

Left ventricular diastolic dysfunction in non-severe chronic obstructive pulmonary disease - a step forward in cardiovascular comorbidome.

Chronic obstructive pulmonary disease (COPD) augments the likelihood of having left ventricular diastolic dysfunction (LVDD)-precursor of heart failure with preserved ejection fraction (HFpEF). LVDD shares overlapping symptomatology (cough and dyspnea) with COPD. Stress induced LVDD is indicative of masked HFpEF. Our aim was to evaluate the predictive value of inflammatory, oxidative stress, cardio-pulmonary and echocardiographic parameters at rest for the diagnosis of stress LVDD in non-severe COPD patients, who complain of exertional dyspnea and are free of overt cardiovascular diseases. A total of 104 COPD patients (26 patients with mild and 78 with moderate COPD) underwent echocardiography before cardio-pulmonary exercise testing (CPET) and 1-2 minutes after peak exercise. Patients were divided into two groups based on peak average E/e': patients with stress induced left ventricular diastolic dysfunction (LVDD)-E/e' > 15 masked HFpEF and patients without LVDD-without masked HFpEF. CPET and echocardiographic parameters at rest were measured and their predictive value for stress E/e' was analysed. Markers for inflammation (resistin, prostaglandine E2) and oxidative stress (8-isoprostanes) were also determined. Stress induced LVDD occurred in 67/104 patients (64%). Those patients showed higher VE/VCO2 slope. None of the CPET parameters was an independent predictor for stress LVDD.Except for prostglandine E2, none of the inflammatory or oxidative stress markers correlated to stress E/e'. The best independent predictors for stress LVDD (masked HFpEF) were RAVI, right ventricular parasternal diameter and RV E/A >0.75. Their combination predicted stress LVDD with the accuracy of 91.2%. There is a high prevalence of masked HFpEF in non-severe COPD with exertional dyspnea, free of overt cardiovascular disease. RAVI, right ventricular parasternal diameter and RV E/A >0.75 were the only independent clinical predictors of masked HFpEF. 288.

On the Probable Change of the Status of the Current Unusual Failure of 11-Year Solar Cyclicity from Local to Global

The anomalous increase in the area of the 23rd solar cycle detected by galactic cosmic rays (GCRs) was a precursor of failure of the 11-year cyclicity: in accordance with the author’s hypothesis about the invariant of the 22-year cycle, an increase in the area of the 23rd cycle was followed by a decrease in the area (energy intensity) of the next 24th cycle. A decrease in energy intensity is accompanied by a decrease (relative variation) in the luminosity of the Sun, which in the 24th cycle has decreased to the level of the average value of the three previous cycles, i.e., almost twice. If the invariant of the 22-year cycle is preserved, the restoration of the 11-year cyclicity in the 25th cycle should be expected. If the invariant of the 22-year cycle is violated, the level of the GCR radiation background at the maximum of the forthcoming 25th cycle (from 2024 to 2025) should not be lower than the background radiation level at the maximum of the 24th cycle (2014). In this case, the state of the 23rd–24th–25th cycle unusual failure will change from local to global.

93137 Interrogating cardio-protective MTSS1 variants in human populations

ABSTRACT IMPACT: It is our hope that a better understanding of the relationship between genetic variants that influence heart failure precursor traits will not only inform clinical care, but enable better assessment of inherited risk and will identify new biological targets for drug development. OBJECTIVES/GOALS: In this project, using a large-scale human genomic dataset with extensive phenotype data available, we intend to interrogate the known MTSS1 variants that have been associated with heart failure (HF) in previous GWAS studies in order to understand the directionality and mechanisms of their effects. METHODS/STUDY POPULATION: Data was obtained from the UK Biobank, a large prospective cohort of ˜500,000 patients across the United Kingdom with extensive phenotype data, including ˜50,000 patients with cardiac MRI and ˜200,000 with whole exome sequencing. We test for associations between genetic variants at the MTSS1 locus and HF precursor traits using logistic regression or linear regression, adjusting for age, gender, and principal components (PCs) of ancestry. For rare variant analyses we ‘bin’ rare variants (MAF < 0.01) using the software tool BioBin to aggregate low frequency genetic variants into single genetic units. RESULTS/ANTICIPATED RESULTS: Preliminary data have shown that variants in the known MTSS1 enhancer region which reduce MTSS1 expression are associated with smaller, more contractile hearts. We anticipate that common variants known to reduce enhancer activity will attenuate heart failure precursor traits, will be associated with a reduced risk clinical heart failure, and will favorably impact clinical outcomes once HF is established. We also anticipate that rare exonic variants predicted to impair MTSS1 function will attenuate heart failure precursor traits. DISCUSSION/SIGNIFICANCE OF FINDINGS: Through this work, we intend to take advantage of multiple novel approaches to better understand a complex disease process, identify a new potential therapeutic target (namely one that targets cardiac function), and to determine which patient subgroups will benefit from this our therapeutic interventions and why.

Characteristic analysis of acoustic emission monitoring parameters for crack propagation in UHPC-NC composite beam under bending test

Ultra high performance concrete (UHPC) has more outstanding mechanical properties and durability than normal concrete (NC) materials. Currently, analysis methods for the mechanical properties of UHPC structures and UHPC composite structures, such as measuring structural deflection, strain, and observing crack propagation, are relatively single. Acoustic emission (AE) technique is a non-destructive testing method that evaluates the damage state of structures effectively. The variation characteristics of AE parameters can be used to analyze the damage process and the failure precursor information of the structures. On this basis, AE technique was used to monitor the crack propagation of the UHPC-NC composite beam under four-point bending test in this study. Results showed that the U-shape UHPC layer gave full play to its high strength and ductility characteristics under bending, which was mainly manifested in reducing the number and width of cracks of the UHPC-NC composite beam, reducing the mid-span deflection and increasing the cracking load (Pcr) and ultimate load (Pu). AE ringing counts, energy, and b-value showed different and easily distinguishable variation characteristics at each failure stage of UHPC-NC composite beam and can be considered the optimal AE monitoring parameters. RA-AF association analysis can be used to further analyze the failure mode of UHPC-NC composite beam. AE monitoring method can be considered an alternative to traditional monitoring methods for the real-time monitoring of crack propagation in UHPC-NC composite beams.

Study on the effect of water on electromagnetic radiation characteristics of fractured sandstone under load

A large number of electromagnetic radiation (EMR) signals are released during loading failure of rock mass, and these signals which contain complex and abundant fracture information can provides precursor of rock mass instability. In order to investigate the effect of water on the EMR characteristics of fractured sandstone, a uniaxial compression experiment was performed on the dried and saturated sandstone samples with prefabricated parallel double cracks. The EMR signals during loading failure of rock samples were acquired and their mechanical properties and EMR signal characteristics were analyzed. Besides, the precursor of rock sample instability was extracted based on the critical slowing down theory. The experimental results show that compared with the dried rock sample, the saturated rock sample has lower compressive strength, starts to crack earlier, and exhibits a more complicated failure mode. During the loading failure of rock samples, their EMR signals respond well to the fracturing and damage. The cumulative number of pulses of saturated rock sample grows uniformly, while that of dried rock sample show a “gentle-violent” rising mode. Moreover, the cumulative number of pulses of dried rock sample is greater than that of saturated rock sample. Water reduces the crack initiation stress level, and the saturated rock sample is the first to experience a sudden jump of EMR pulse. With the increase of the loading stress, the dominant frequency of EMR gradually transitions from low frequency to high frequency. Compared with dried rock samples, saturated rock samples have a lower proportion of high-frequency signals. Since the dominant mechanism of EMR varies with the change of failure stage, water first promotes the EMR signals of rock samples in the early stage of loading; then, it weakens the EMR signals in the middle and late stages of loading. Based on the critical slowing down theory, the EMR pulse signals were analyzed, which conduces to the extraction of potential precursor of rock sample failure and instability. Compared with dried rock samples, the precursory characteristic of saturated rock sample is more obvious. The research results provide some guidance for the stability of water-bearing fractured rock mass and the monitoring and early warning of related geological hazards.

Using the characteristics of infrared radiation b-value during the rock fracture process to offer a precursor for serious failure

The Infrared Radiation (IR) on the surface of a rock being loaded will change significantly during its failure process. To effectively monitor and predict rock failure by the IR method, in this paper, the Infrared Radiation Variation Temperature Field (IRVTF) of rock under uniaxial compression was identified. It was found that some IRVTF thermal images were characterized by obvious temperature rise in the later stage of rock loading. The temperature distribution characteristics of IRVTF were analyzed. It was observed that the temperature of the IRVTF exhibited the logarithmic linear distribution within the selected statistical temperature range, with an average coefficient of correlation greater than 0.96. On this basis, the index of “Infrared Radiation b-value (bIR-value)” of rock under uniaxial compression was defined for the first time, and the threshold for identifying its sudden change was proposed. It was found that the sudden changes of bIR-value could be observed with the generation of large-scale micro-cracks. The average amplitude of the bIR-value at first sudden change for all samples was 16.58 times of the mean amplitude before the sudden change on average, which indicated the significance of the bIR-value sudden change. The first sudden change of the bIR-value was 22.5 s ahead of the peak stress on average, which could be used as a precursor of rock failure and instability. The findings of the research can help with the monitoring and early warning of surrounding rock instability in mines, tunnels, and other geotechnical projects.

Multiscale modeling of distributed microcracking in concrete

AbstractConcrete is a quasi‐brittle material with a heterogeneous morphology across multiple scales, which also influences the evolution of damage in case of loading. Damage in concrete structures is initiated by growth of diffuse microcracks that is followed by damage localization eventually leading to structural failure. Thus, diffuse microcracking processes can be considered as failure precursors. Identification and characterization of these precursors can be applied in conjunction with structural health monitoring based on diffuse ultrasonic waves to develop early warning systems against catastrophic failure of concrete structures. To this end, a multiscale model for a simulation‐based description of diffuse damage in concrete is proposed. At the scale of the cement paste, microcrack growth is modeled by a combination of continuum micromechanics and linear elastic fracture mechanics [1]. The micromechanics model is incorporated into a reduced‐order Lippmann‐Schwinger based meso‐model for concrete [2], [3]. The mesoscale model is generated using Random Sequential Adsorption of realistic aggregates based on concave slicing of randomly cut polyhedrons. The influence of the microcrack morphology at the microscale on the diffuse microcracking and overall concrete stiffness degradation is presented.

A MOSFET SPICE Model With Integrated Electro-Thermal Averaged Modeling, Aging, and Lifetime Estimation

Lifetime estimation of power semiconductor devices have been widely investigated to improve the reliability and reduce the cost of maintenance of power converters. However in most reported work, the aging effect is not considered in the lifetime evaluation process due to the omission or limitation of thermal cycle counting method. Additionally, the electrical/thermal simulation and lifetime estimation are usually implemented in different simulators/platforms, for the same reason. Thus, to tackle these problems, a concise but comprehensive MOSFET model that enables electro-thermal modeling, aging and lifetime estimation on LTspice® circuit simulator is proposed in this paper. The idea comes from the fact that, MOSFET on-state resistance $R_{ds,on}$ is not only temperature dependent, but also widely accepted as the device failure precursor. In other words, as it carries critical information about instantaneous temperature and aging progress. Hence, co-simulation can be achieved by constructing electrical, thermal, and aging and lifetime sub-modules exclusively first, and using $R_{ds,on}$ , to build linkages among them. Averaged modeling technique is adopted due to the ease of establishing links among these three sub-modules, and fast simulation speed as compared to a switched converter model. Behavioral models are employed to realize the thermal cycles counting, stress accumulation and degradation evaluation. This paper demonstrates that it is possible to use a single simulation software to monitor performances of devices and circuits, and their lifetime estimation simultaneously. High-stress thermal cycling and long-term random mission profiles are applied to verify the correctness of the model and to mimic a 10-year load respectively. An accelerated aging trend can be observed in the long-term mission profile simulation, which is in agreement with the theory. Facilitated by the employment of averaged circuits, the proposed method is a good simulation/analytical tool to implement a long-term mission profile that requires reliability assessment.

Predicting rock failure with the critical slowing down theory

Early warning signals of critical transitions in rock before its sudden failure are key for forecasting geological disasters in rock engineering. Here we examined the critical slowing down characteristics of acoustic emission (AE) and precursory signals preceding catastrophic rock failure. We conducted laboratory experiments on different types of rock specimens subjected to tension and compression, instrumented by real-time AE monitoring. Based on the critical slowing down theory, AE signals monitored over the deformation and failure of the rock specimens were parametrized statistically. The results show that the critical slowing down characteristics of AE signals exist for rocks under various experimental conditions. The sudden and significant increase in the variance and the autocorrelation coefficient of AE can be used as precursors for rock failure. The time intervals between the precursory signals and rock rupture for brittle rocks under tension are smaller than those under compression. These early warning time intervals are longer and the ratios of the early warning to peak states are lower during Brazilian tests than during direct tensile tests. Furthermore, relationships between multiple influencing factors and precursory signals were discussed. We found that the precursory signals are strongly related to the intrinsic properties of rock and the external experimental conditions. Finally, the applicability and reliability of precursory signals through the critical slowing down theory were verified for rock failure by statistically analysing the laboratory data from a wide range of rocks.

Cyclic fatigue characteristics of rock failure using infrared radiation as precursor to violent failure: Experimental insights from loading and unloading response

AbstractIn this research paper, a new method is developed that can be used as a precursor of violent rock failure. It is based on measuring the characteristics of rock failure using infrared radiation (IR) under uniaxial cyclic loading and unloading. The loading–unloading response ratio (LURR) is determined based on IR indexes such as average infrared radiation temperature (AIRT) and infrared radiation temperature rate (IRTR). The results show that the LURR based on AIRT revealed an overall rising trend and mutation that occurred in the last cycle, which can be used as a precursor of the imminent rock failure. By contrast, the LURR based on IRTR has a noticeable ‘mutation‐rapid decrease’ in the middle and later periods of cyclic loading and unloading, which can also be considered as an early precursor of rock failure. Combined with the precursors of the imminent rock failure, the categorized warning of rock failure is recognized.

A low quiescent power wireless rotating machinery condition monitoring system

Vibration-based monitoring of rotating machinery is rapidly evolving within the aerospace industry with priority on detecting impending failures. The workhorse of such monitoring system remains a piezoelectric-based accelerometers which requires a wired-harnesses, connectors, significant power, and signal conditioning, etc. Raytheon Technologies Research Center (RTRC) along with Collins Aerospace and Sandia National Laboratory have jointly developed an Aluminum-Nitride Resonant Integrated Accelerometer Sensors (ARISE). 
 This is a low power alternate for a conventional wired vibration-based monitoring system. This self-contained sensor system includes: (1) a low quiescent power sensing element with a wake-up module, (2) a wireless communication module, and (3) a coin-cell battery. Leveraging work performed under Defense Advanced Research Projects Agency (DARPA) N-Zero program. This wireless health monitoring system can operate in a quiescent low power mode (~10nW) for a period of several years without servicing. With an exceedance above a preset vibration level (at designate characteristic frequencies), the sensor wakes up and wirelessly sends a warning of a precursor-to-failure.
 The ARISE sensor and wake-up module package has been validated with a replicated vibration environment acquired from a selected rotating machinery subject to progressive damage at the Structural Dynamics Laboratory at RTRC. The failure precursor is successfully detected by the sensor which triggers the wake-up module.
 This research was developed with funding from the Defense Advanced Research Projects Agency (DARPA) Micro Technology Office (MTO), under Aluminum-Nitride Resonant Integrated Accelerometer Sensors (ARISE) program.

Evaluation of the Correlation Coefficient as a Prognostic Indicator for Electromechanical Servomechanism Failures

In order to identify incipient failures due to a progressive wear of a primary flight command electromechanical actuator, several approaches could be employed; the choice of the best ones is driven by the efficacy shown in fault detection/identification, since not all the algorithms might be useful for the proposed purpose. In other words, some of them could be suitable only for certain applications while they could not give useful results for others. Developing a fault detection algorithm able to identify the precursors of the abovementioned electromechanical actuator (EMA) failure and its degradation pattern is thus beneficial for anticipating the incoming malfunction and alerting the maintenance crew such to properly schedule the servomechanism replacement. The research presented in the paper was focused to develop a fault detection/identification technique, able to identify symptoms alerting that an EMA component is degrading and will eventually exhibit an anomalous behavior, and to evaluate its potential use as prognostic indicator for the considered progressive faults (i.e. frictions and mechanical backlash acting on transmission, stator coil short circuit, rotor static eccentricity). To this purpose, an innovative model based fault detection technique has been developed merging several information achieved by means of Fast Fourier Transform (FFT) analysis and proper "failure precursors" (calculated by comparing the actual EMA responses with the expected ones). To assess the performance of the proposed technique, an appropriate simulation test environment was developed: the results showed an adequaterobustness and confidence was gained in the ability to early identify an eventual EMA malfunctioning with low risk of false alarms or missed failures.

The Cardiac Fibroblast in heart failure – an inflammatory cell

Abstract Introduction Cardiac inflammation with subsequent remodeling of the extracellular matrix (ECM) with fibrosis formation is an important precursor of heart failure. In myocardial inflammation release of cytokines, such as TNF-α was previously linked to the development of fibrosis. However, their exact role in fibroblasts activation, leading to their transformation into myofibroblasts and ultimately fibrosis is unknown. Therefore, the purpose of this work was to study the secretome of isolated cardiac fibroblasts of heart failure patients in vitro. Methods and results Human cardiac fibroblasts were obtained from endomyocardial biopsies of patients with reduced ejection fraction. Secretome- and gene expression analysis was performed on TNF-α (10 ng/ml) and TGF-β (5 ng/ml) treated and untreated fibroblasts. The analysis of the secretome in cell culture supernatant of these fibroblasts was performed by nano-LC-ESI tandem mass spectrometry. Subsequently, RNA was isolated from fibroblasts and expression analysis was performed using affymetrix gene chips and verified for the stimulation experiments using TaqMan. The secretome and gene expression studies are constistent regarding the most frequent ECM components. The proteins involved in the construction of the ECM accounted for 56% of the total protein intensity. The fibronectin represented the largest proportion of ECM proteins (50%), with collagens accounting for 29% and MMPs and TIMPs for approximately 5% and a small proportion of cytokines. In the secretome as well as in the gene expression, Il-6 and Il-8 showed the highest proportion of cytokines and type I as well as type IV (each approx. 40%) of collagens. MMP2, MMP1 and TIMP1 accounted for the largest proportion of MMPs and TIMPs. Stimulation with TGF-β and TNF-α led to changes in the composition of the cytokines and ECM proteins. After the stimulation with TNF-α, the proportion of cytokines increased from 3.1% to 6.6%, while the proportion of ECM proteins decreased slightly. Accordingly, after stimulation with TGF-β a well-known inductor of fibrosis, the proportion of collagens and other matrix proteins increased, while the proportion of cytokines decreased slightly. Conclusion In this study, we identified the most abundant proteins of the ECM and demonstrated their expansion caused by TGF-β stimulation of fibroblasts. Surprisingly, TNF-α led to an increase of cytokines secreted by the fibroblasts with a minimal reduction of ECM proteins. Here, the differentiated regulation of the fibroblast in the transformation of the ECM could be seen. TNF-α stimulation demonstrated to increase gene expression of the cytokines in fibroblasts, which in turn maintain inflammation with chemotactic effect. Hence, cardiac fibroblasts seem to be supporting cells for cardiac inflammation. There seemed to be no pro-fibrotic effect. In this work we could show the pro-inflammatory role of the cardiac fibroblast upon inflammatory stimulation. Funding Acknowledgement Type of funding source: None

Evaluation of internal microcrack evolution in red sandstone based on time–frequency domain characteristics of acoustic emission signals

Rocks are commonly used as building stone and construction materials in many engineering applications. To study the internal microcrack evolution characteristics of red sandstone specimens during deformation and failure, a uniaxial compression experiment was conducted based on RMT-150C rock mechanics, PCI-II acoustic emission (AE), and the strain acquisition testing systems. For eight red sandstone specimens, the relationships among axial stress, axial strain, acoustic emission events rate, and average frequency centroid were established. The variability of the AE events rate and average frequency centroid of the specimens was analyzed for five cracking levels. Additionally, the relationship between the loading stress corresponding to the minimum average frequency centroid of the AE signals and the peak stress during deformation and failure of the red sandstone specimens was discussed, and critical failure precursor characteristics revealed. Moreover, statistical analysis of the AE signal distribution characteristics of different frequency bands and amplitudes during rock deformation and failure was performed. Based on the difference between the AE signal duration ratio and the specimen rise time, a method for extracting AE characteristic signals during deformation and failure was proposed. Time-frequency analysis was performed on the extracted AE characteristic signals and results showed that the signals were closely related to the axial stress–strain change in the specimens, and were affected by the degree and development of internal microcracks. The wave peaks of the crack closure and linear elastic deformation stage AE characteristic signal frequency domain waveforms are relatively scattered. The wave peaks of the frequency-domain waveforms of the AE characteristic signals during stable and unstable crack growth stages are relatively concentrated.

Myocardial Steatosis Among Antiretroviral Therapy-Treated People With Human Immunodeficiency Virus Participating in the REPRIEVE Trial.

People with human immunodeficiency virus (PWH) face increased risks for heart failure and adverse heart failure outcomes. Myocardial steatosis predisposes to diastolic dysfunction, a heart failure precursor. We aimed to characterize myocardial steatosis and associated potential risk factors among a subset of the Randomized Trial to Prevent Vascular Events in HIV (REPRIEVE) participants. Eighty-two PWH without known heart failure successfully underwent cardiovascular magnetic resonance spectroscopy, yielding data on intramyocardial triglyceride (IMTG) content (a continuous marker for myocardial steatosis extent). Logistic regression models were applied to investigate associations between select clinical characteristics and odds of increased or markedly increased IMTG content. Median (Q1, Q3) IMTG content was 0.59% (0.28%, 1.15%). IMTG content was increased (> 0.5%) among 52% and markedly increased (> 1.5%) among 22% of participants. Parameters associated with increased IMTG content included age (P = .013), body mass index (BMI) ≥ 25 kg/m2 (P = .055), history of intravenous drug use (IVDU) (P = .033), and nadir CD4 count < 350 cells/mm³ (P = .055). Age and BMI ≥ 25 kg/m2 were additionally associated with increased odds of markedly increased IMTG content (P = .049 and P = .046, respectively). A substantial proportion of antiretroviral therapy-treated PWH exhibited myocardial steatosis. Age, BMI ≥ 25 kg/m2, low nadir CD4 count, and history of IVDU emerged as possible risk factors for myocardial steatosis in this group. NCT02344290; NCT03238755.

Failure characteristics and physical signals of jointed rock: an experimental investigation

Jointed rock mass stability is a constant focus in underground engineering applications. In this study, the uniaxial compression test is carried out on defective red sandstone with different defect angles by using cement to simulate the defects. The physical characteristics of the strain and the acoustic emission energy released during the failure of the jointed rock mass are monitored by means of strain and acoustic emission methods. The experimental results indicate that with the difference in the defect angle, the failure mode of the jointed rock sample changes, and the instability signal released during the failure process is also different. When the angle of the defective part is small, within 15°, the failure modes of the defects are similar to those of the intact rock sample. When the defect angle is between 15° and 60°, the failure modes of the defects begin to transition from tensile failure to shear failure. With the increase in the defect angle, the failure process of the jointed rock sample becomes faster and it becomes more difficult to capture the instability signal. When the angle of the defect part is smaller than 45°, the overall instability of the jointed rock sample can be determined by measuring the physical signal released in the static sub-instability stage. When the angle of the defect part increases, the instability can only be determined based on the physical signal released from the previous stage, that is, the strong deviation from the linear stage. The experimental method used in this paper could be used to identify failure precursors of jointed rock masses and to develop technology for disaster prevention in rock engineering.

Effects of moisture conditions on mechanical properties and AE and IR characteristics in coal–rock combinations

Mining disturbances may cause fissure water in the sandstones of a coal seam roof to link up with the coal seam, further causing changes in the moisture conditions of coal–rock systems such as immediate roofs, coal seams, and immediate floors. The varying moisture content influences the mechanical properties and failure precursor symptoms of coal–rock systems. In this study, we carried out uniaxial compressive experiments on coal–rock combinations under dry, natural moisture, and saturated conditions and measured the acoustic emission (AE) and infrared radiation (IR) data. The results show that the combinations can be classified according to the varying water absorption capacities of coal, mudstone, and siltstone with intrusion time. We classified them into a rapid water absorption stage (0 to 2 h), a slow water absorption stage (> 2 to 14 h), and a stable stage (> 14 h). At the same stage, the water absorption capacities can be ranked as coal > mudstone > siltstone. From dry to saturated, the uniaxial compressive strengths, modulus of elasticity, and peak strain of the coal–rock combination specimens is reduced by 37.5, 8.9, and 35.2% respectively. Cracks produced by coal–rock combinations were concentrated mainly on the surface of the coal portions. Before and after the peak failure, the IR temperature of the dry coal–rock combination increases first and then decreases, while the IR temperature of the natural moisture and saturated coal–rock combinations decreases first, then increases, then decreases again. From dry to saturated, the time interval and stress-level interval between the AE precursor point and IR precursor point of the specimens increases by 1.68 times and 4.5 times, respectively. These outcomes provide a useful reference for studying monitoring and early warning of coal and rock interactions and coal and rock pillar instability under the effect of water–rock interaction in engineering practice.

Precursors of the treatment failure of mycobacteriosis in patients with HIV

Purpose. Analyze the dynamics of clinical and laboratory parameters, the outcomes of the disease on various treatment regimens. To identify the main markers of unfavorable outcome or protracted course of the disease. Materials and methods. The study included 70 patients with HIV and mycobacteriosis who received complex therapy (antiretroviral and specific antibacterial drugs). Depending on the outcome of the disease, two groups were distinguished: clinical cure (n = 38) and lethal outcome (n = 32). The clinical manifestations of pathology, laboratory indicators at different stages of treatment, the scheme and terms of the therapy being carried out were analyzed on the basis of data from medical histories and ambulatory patient records. A statistical analysis was performed, the efficacy of therapy was evaluated using the Kaplan-Meier method, the macrolide in the first line of antibacterial therapy used was taken as the basis. Results. All patients who died developed a disseminated form of the process. In cases when MAI developed within the unmasking immune restoration syndrome patients were prognostically more favorable (p &lt;0,05). In the clinical cure group, a significantly higher level of CD4 lymphocytes was recorded before treatment (33,3 ± 7,1 versus 9,9 ± 3,2 cells / μl, p &lt;0,05). A significant difference in the level of CD4 persisted after a month of complex therapy (79,0 ± 13,4 versus 32,2 ± 9,1, p &lt;0.05). In addition to higher immunity values, the first group also had a higher hemoglobin level after a month of treatment (108,3 ± 3,2 g / l versus 76,7 ± 5,2 g / l, p &lt;0,05). The regression of intoxication and fever was observed earlier in the cure group. When studying the used macrolide basis for the treatment of mycobacteriosis, it was found that survival term was significantly higher among patients who received clarithromycin in the first line (Kaplan – Meier, p &lt;0,05 Breslow, Tarone-Ware). According to this sample, the introduction of aminoglycoside to the treatment regimen did not make significant changes in the timing and prognosis of treatment. Conclusion . Prolonged persistence of the symptoms of the disease, persisting deep immunodeficiency and anemia of moderate or severe degree are associated with an unfavorable outcome. According to this sample, clarithromycin should be considered the drug of choice for the treatment of mycobacteriosis in HIV.

Using the characteristics of infrared radiation during the process of strain energy evolution in saturated rock as a precursor for violent failure

Water saturated rock strain energy evolution was measured using infrared radiation (IR) under uniaxial load of sandstone samples. The variation in the characteristics of total strain, elastic strain, dissipated strain energies and maximum IR of saturated rock under stress were analyzed. The results reveal the degree of saturation has a significant effect on rock strain energy. The total strain and elastic strain energies correlated linearly negatively, dissipative strain energy were correlated exponentially negatively, and maximum infrared radiation variance (IRV) correlated quadratically at peak stress point with different degree of saturation of rock samples. The relationship between total strain, elastic strain energies, and ΔIRV was a linear function under different saturated conditions. It was found that there was a linear energy transfer and linear energy storage function in the rock. Based on linear energy transfer and storage, two coefficient in the presence of IR were introduced, i.e., the Total Energy Infrared Radiation Coefficient (TEIRC) and Energy Storage Infrared Radiation Coefficient (ESIRC). These can be used with variation in infrared radiation variance (ΔIRV) to determine total strain and elastic strain energies of saturated rock. Furthermore, a quantitative analysis index of energy dissipation infrared radiation ratio (EDIRR), i.e. the ratio of dissipative strain energy to ΔIRV, has been proposed which can be used to predict and identify the failures of saturated rock. The inflection point of rock EDIRR from horizontal to rapid growth can be regarded as the precursor point for rock failure, and the EDIRR mutation after the precursor point can be used as the new criterion to monitor rock failure and instability.