Coupled effects of stress damage and drilling fluid on strength of hard brittle shale

During well drilling process,original stress state of hard brittle shale will be changed due to stress redistribution and concentration,which leads to stress damage phenomenon around the borehole.Consequently,drilling fluid will invade into formation along the tiny cracks induced by stress damage,and then weaken the strength of hard brittle shale.Based on this problem,a theoretical model was set up to discuss damage level of shale under uniaxial compression tests using acoustic velocity data.And specifically,considering the coupled effect of stress damage and drilling fluid,the relationship between hard brittle shale strength and elapsed time was analyzed.

Moderate Dose of Trolox Preventing the Deleterious Effects of Wi-Fi Radiation on Spermatozoa In vitro through Reduction of Oxidative Stress Damage

Background： The worsening of semen quality, due to the application of Wi-Fi, can be ameliorated by Vitamin E. This study aimed to demonstrate whether a moderate dose of trolox,a new Vitamin E,inhibits oxidative damage on sperms in vitro after exposure to Wi-Fi radiation. Methods： Each of the twenty qualified semen, gathered from June to October 2014 in eugenics clinic, was separated into four aliquots, including sham, Wi-Fi-exposed, Wi-Fi plus 5 mmol/L trolox, and Wi-Fi plus 10 mmol/L trolox groups. At 0 min, all baseline parameters of the 20 samples were measured in sequence. Reactive oxygen species, glutathione, and superoxide dismutase were evaluated in the four aliquots at 45 and 90 min, as were sperm DNA fragments, sperm mitochondrial potential, relative amplification of sperm mitochondrial DNA, sperm vitality, and progressive and immotility sperm. The parameters were analyzed by one-way analysis of variance and Tukey＇s posttest. Results： Among Wi-Fi plus 5 mmol/L trolox, Wi-Fi-exposed and Wi-Fi plus 10 mmol/L trolox groups, reactive oxygen species levels （45 min： 3.80 ± 0.41 RLU·10^-6·ml^-1. 7.50 ± 0.35 RLU·10^-6·ml^-1vs. 6.70 ± 0.47 RLU·10^-6·ml^-1P 〈 0.001; 90 min：5.40 ± 0.21 RLU·10^-6·ml^-1vs. 10.10 ± 0.31 RLU·10^-6·ml^-1. 7.00 ± 0.42 RLU·10^-6·ml^-1P 〈 0.001, respectively）, percentages of tail DNA （45 min： 16.8 ± 2.0% vs. 31.9 ± 2.5% vs. 61.3 ± 1.6%, P 〈 0.001; 90 min： 19.7 ± 1.5% vs. 73.7 ± 1.3% vs. 73.1 ± 1.1%, P 〈 0.001, respectively）, 8-hydroxy-2＇-deoxyguanosine （45 min： 51.89 ± 1.46 pg/ml vs. 104.89 ± 2.19 pg/ml vs. 106.11 ± 1.81 pg/ml , P = 0.012;90 min： 79.96 ± 1.73 pg/ml vs. 141.73 ± 2.90 pg/ml vs. 139.06 ± 2.79 pg/ml; P 〈 0.001）, and percentages of immotility sperm （45 min：27.7 ± 2.7% vs. 41.7 ± 2.2% vs. 41.7 ± 2.5%; 90 min： 29.9 ± 3.3% vs. 58.9 ± 4.0% vs. 63.1 ± 4.0%; all P 〈 0.001） were lowest, and glutathione peroxidase （45 min： 60.50 ± 1.54 U/ml vs. 37.09 ± 1.77 U/ml vs. 28.18 ± 1.06 U/ml; 90 min： 44.61 ± 1.23 U/ml vs. 16.86 ± 0.93 U/ml vs. 29.94 ± 1.56 U/ml; all P 〈 0.001）, percentages of head DNA （45 min： 83.2 ± 2.0% vs. 68.2 ± 2.5% vs. 38.8 ± 1.6%; 90 min： 80.3 ± 1.5% vs. 26.3 ± 1.3% vs. 26.9 ± 1.1%; all P 〈 0.001）, percentages of sperm vitality （45 min： 89.5 ± 1.6% vs. 70.7 ± 3.1% vs. 57.7 ± 2.4%;90 min： 80.8 ± 2.2% vs. 40.4 ± 4.0% vs. 34.7 ± 3.9%; all P 〈 0.001）, and progressive sperm （45 min： 69.3 ± 2.7% vs. 55.8 ± 2.2% vs. 55.4 ± 2.5%; 90 min： 67.2 ± 3.3% vs. 38.2 ± 4.0% vs. 33.9 ± 4.0%; all P 〈 0.001） were highest in Wi-Fi plus 5 mmol/L trolox group at 45 and 90 min, respectively. Other parameters were not affected, while the sham group maintained the baseline. Conclusion：This study found that 5 mmol/L trolox protected the Wi-Fi-exposed semen in vitro from the damage of electromagnetic radiation-induced oxidative stress.

Elimination mechanism of coal and gas outburst based on geo‑dynamic system with stress–damage–seepage interactions

Coal and gas outburst is a complex dynamic disaster during coal underground mining.Revealing the disaster mechanism is of great signifcance for accurate prediction and prevention of coal and gas outburst.The geo-dynamic system of coal and gas outburst is proposed.The framework of geo-dynamic system is composed of gassy coal mass,geological dynamic environment and mining disturbance.Equations of stress–damage–seepage interaction for gassy coal mass is constructed to resolve the outburst elimination process by gas extraction with boreholes through layer in foor roadway.The results show the occurrence of outburst is divided into the evolution process of gestation,formation,development and termination of geo-dynamic system.The scale range of outburst occurrence is determined,which provides a spatial basis for the prevention and control of outburst.The formation criterion and instability criterion of coal and gas outburst are established.The formation criterion F1 is defned as the scale of the geo-dynamic system,and the instability criterion F2 is defned as the scale of the outburst geo-body.According to the geo-dynamic system,the elimination mechanism of coal and gas outburst—‘unloading+depressurization’is established,and the gas extraction by boreholes through layer in foor roadway for outburst elimination is given.For the research case,when the gas extraction is 120 days,the gas pressure of the coal seam is reduced to below 0.4 MPa,and the outburst danger is eliminated efectively.

Protective effects of MCI-186 on oxidative damage in a cell model of Alzheimer's disease

Oxidative stress has an important role in the development of Alzheimer＇s disease （AD）. Beta amyloid protein 25-35 （Aβ25-35） can generate oxygen free radicals, and MCI-186 （3-methyl-l-phenyl-2-pyrazolin-5-one, edaravone） can specifically eliminate hydroxyl radicals. The present study introduced Aβ25-35 into PC12 cells to establish a cell model of AD, and investigated the neuroprotective effects of MCI-186 on AD. Results showed that MCI-186 had a positive effect on the prevention and treatment of AD by inhibiting protein oxidative products, advanced glycation end products, lipid oxidative end products and DNA oxidative damage in PC12 cells induced by Aβ25-35.

DAMAGE TOLERANCE ANALYSIS ON HOLLOW AXLES OF HIGH SPEED MOTOR TRAINS

According to the rules of UIC515-3, the service loads of the axles are defined, which include some different loads cases as follows： the static loads; the impact loads resulted from running through the rail joints and unevenness rails; the loads through curves and from braking. Through the calculating and analysis, the stress distribution of the hollow axles is obtained for 200 km/h high speed motor trains used in China. At the same time, the fatigue crack growth of hollow axles is studied, and the initial surface cracks of 2 mm depth caused by hard objects strike or the other causes are discussed. On the basis of the linear elastic fracture mechanics theory, the stress intensity factor of the crack of the geometry transition outside the wheel seat is also studied. Associated with fatigue crack propagation equation and the corresponding crack propagation threshold, the crack propagation characteristics under different shapes are calculated. Then the running distances are educed with different shapes propagating to the critical length, and the estimation of the residual lives about hollow axles which are the reference values of examine and repair limit of the hollow axle is given.

Effect of electroacupunture on gastric mucosal intestinal trefoil factor gene expression of stress-induced gastric mucosal injury in rats

AIM： To investigate electroacupunture（EA） at the acupoints of Stomach Meridian of Foot-Yangming（SMFY）, Gallbladder Meridian of Foot-Yangming（SMFY） on gastric mucosal intestinal trefoil factor （ITF） gene expression detection in stress-induced rats with gastric mucosal lesion, and to explore the regulatory mechanism and significance of EA-related gastric mucosal protective effect. METHODS： Forty rats were randomly divided into 4 groups： Blank group, Model group, Model group＋EA at acupoints of SMFY group（＂SMFY group＂）, and Model group＋EA at acupoints of GMFY group（GMFY group）. All rats （except blank group） were made model by water immersion and restraint stress （WRS）. Then the gastric mucosa tissue in each rat was taken off alter assessment of gastric mucosal lesion index（GUI）, and the expression of ITF mRNA of the tissues was detected by reverse transcdption-polymerase chain reaction（RT-PCR） method. RESULTS： Compared with Model group（S4.3± 1.34）, the GUI value in SMFY group （31±2.211 decreased significantly（P〈0.01）, so did that in GMFY group （39.8± 1.62, P〈0.05）, meanwhile GUI value in SMFY group was significantly lower than in GMFY group（P〈0.01）. Compared with Model group （0.65±0.01）, EA had a tendency to improve the expression of gastric mucosal ITFmRNA gene： such tendency existed in GMFY group （0.66±0.01） but with no signficant difference（P〉 0.05）, in SMFY group（0.76±0.01） with an extremely obvious difference （P〈0.01）, furthermore the expression in SMFY group was significantly higher than in GMFY group （P〈 0.01）.CONCLUSION： The gastric mucosal protective effect by EA at the acupoints of SMFY and GMFY was related to the expression variance of ITF, indicating certain meridian specificity exists, It could be one proof for the TCM theory ＂Relative pardcularity between SMFY and stomach＂.

Analysis of the stress ratio of anisotropic rocks in uniaxial tests

The effect of structural discontinuities on the progressive failure process of anisotropic rocks should be paid particular attention.The crack damage stress σ_(cd),also considered as the yield strength,and the relationship between σ_(cd) and the uniaxial peak strength σ_(ucs) of anisotropic rocks for different orientations 8 of the isotropy planes with respect to the loading directions were investigated theoretically and experimentally.A theoretical relation of σ_(cd)/σ_(ucs) with the function of the shape parameter m was established.Additionally,uniaxial compression tests of shale samples were conducted for several inclinations θ.The test result of σ_(cd)/σ_(ucs) was close to the theoretical value for a given orientation.Furthermore,both experimental results and theoretical solutions of σ_(cd)/σ_(ucs) were independent of the inclination θ while σ_(cd) andσ_(ucs) were strongly affected by θ.The strength ratio σ_(cd)/σ_(ucs) may therefore be an intrinsic property of anisotropic rocks and could be used to predict the failure of rock samples.

Dynamic Mechanical Characteristics and Damage Evolution Model of Granite

By using the technique of the split Hopkinson pressure bar（ SHPB）,impact tests at different stress wavelengths（ 0. 8-2. 0 m） and strain rates（ 20-120 s^（-1）） were conducted to study the dynamic mechanical properties and damage accumulation evolution lawof granite. Test results showthat the dynamic compressive strength and strain rate of granite have a significantly exponential correlation;the relationship between peak strain and strain rate is approximately linear,and the increase of wavelengths generally makes the level of peak strain uplift. The multiple-impacts test at a lowstrain rate indicates that at the same wavelength,the cumulative damage of granite shows an exponential increasing form with the increase of strain rate; when keeping the increase of strain rate constant and increasing the stress wavelength,the damage accumulation effect of granite is intensified and still shows an exponential increasing form; under the effect of multiple impacts,the damage development trend of granite is similar overall,but the increase rate is accelerating. Therefore the damage evolution model was established on the basis of the exponential function while the physical meaning of parameters in the model was determined. The model can reflect the effect of the wave parameters and multiple impacts. The validity of the model and the physical meaning of the parameters were verified by the test,which further offer a reference for correlational research and engineering application for the granite.

A swallow-tail type catastrophic model of earthquake process

This paper considers the effects of damage softening and hydraulic softening on fault zone media and provides a nonlinear mechanics model of fault earthquake. Taking far field displacement,stiffness ratio and permeation parameter as control variables, we obtain a swallowtail type catastrophic model of earthquakes. Then, by this model, we study the effects of permeation, far field displacement and stiffness ratio on the preparation and the occurrence of earthquakes.

Predicting triaxial compressive strength of high-temperature treated rock using machine learning techniques

The accurate prediction of the strength of rocks after high-temperature treatment is important for the safety maintenance of rock in deep underground engineering.Five machine learning(ML)techniques were adopted in this study,i.e.back propagation neural network(BPNN),AdaBoost-based classification and regression tree(AdaBoost-CART),support vector machine(SVM),K-nearest neighbor(KNN),and radial basis function neural network(RBFNN).A total of 351 data points with seven input parameters(i.e.diameter and height of specimen,density,temperature,confining pressure,crack damage stress and elastic modulus)and one output parameter(triaxial compressive strength)were utilized.The root mean square error(RMSE),mean absolute error(MAE)and correlation coefficient(R)were used to evaluate the prediction performance of the five ML models.The results demonstrated that the BPNN shows a better prediction performance than the other models with RMSE,MAE and R values on the testing dataset of 15.4 MPa,11.03 MPa and 0.9921,respectively.The results indicated that the ML techniques are effective for accurately predicting the triaxial compressive strength of rocks after different high-temperature treatments.

Prophylactic treatment with growth hormone improves intestinal barrier function and alleviates bacterial translocation in stressed rats

Background Damage to the gut barrier often occurs during critical illnesses. In such cases, it is very important to alleviate impairment of the intestinal barrier and protect intestinal barrier function. This study investigated the protective effect of growth hormone on intestinal barrier function in rats under stress.Methods This study consisted of prospective, randomized, and controlled animal experiments. Twenty-five Sprague-Dawley rats served as total parenteral nutrition (TPN) models and were divided into three groups: TPN group, sepsis (Sep) group, and growth hormone (GH) group. Another 8 rats served as normal controls. Each group received different stress stimuli. Rats were fed for 7 days, and samples were taken for examination 24 hours after gavaging with dual saccharides.Results The architecture of the small intestinal mucosa in the Sep group showed the most severe damage among all groups. Nitric oxide levels in blood plasma and immunoglobulin A levels in the intestinal mucosa of the GH group were significantly lower than in the Sep group (P<0. 02). There were no significant changes in CD3 counts and in the CD4/CD8 ratio between the four groups. Dual sugar tests and bacteriological examinations revealed that intestinal permeability and rate of bacterial translocation in the GH group were lower than in the Sep group (P<0. 01, respectively).Conclusion Prophylactic treatment with growth hormone can alleviate damage to intestinal barrier function caused by trauma and endotoxemia in rats under stress.

Research of Step-down Stress Accelerated Degradation Data Assessment Method of a Certain Type of Missile Tank

The performance degradation rates of the missile tank are generally time-varying functions uneasily evaluated by general classical evaluation methods. This paper develops a segmented nonlinear accelerated degradation model （SNADM） based on the equivalent method of accumulative damage theory, which tackles the problem that product life is difficult to be determined with degradation rate being a function of the variable of time. A segmented expression of the function of population accumulative degradation is derived. And combined with nonlinear function, an accelerated degradation function, i.e., SNADM is obtained. The parameters of the SNADM are identified by numerical iteration, and the statistical function of degradation track is extrapolated. The reliability function is determined through the type of random process of the degradation distribution. Then an evaluation of product storage life is undertaken by combining the statistical function of degradation track, reliability function and threshold. An example of a missile tank undergoes a step-down stress accelerated degradation test （SDSADT）, in which the results with the SNADM and the classical method are evaluated and compared. The technology introduced is validated with the resultant coincidence of both evaluated and field storage lives.

Genotoxicity of ferric oxide nanoparticles in Raphanus sativus：Deciphering the role of signaling factors,oxidative stress and cell death

We have studied the genotoxic and apoptotic potential of ferric oxide nanoparticles（Fe_2O_3-NPs） in Raphanus sativus（radish）.Fe_2O_3-NPs retarded the root length and seed germination in radish.Ultrathin sections of treated roots showed subcellular localization of Fe_2O_3-NPs,along with the appearance of damaged mitochondria and excessive vacuolization.Flow cytometric analysis of Fe_2O_3-NPs（1.0 mg/m L） treated groups exhibited 219.5%,161%,120.4% and 161.4% increase in intracellular reactive oxygen species（ROS）,mitochondrial membrane potential（ΔΨm）,nitric oxide（NO） and Ca2＋influx in radish protoplasts.A concentration dependent increase in the antioxidative enzymes glutathione（GSH）,catalase（CAT）,superoxide dismutase（SOD） and lipid peroxidation（LPO） has been recorded.Comet assay showed a concentration dependent increase in deoxyribonucleic acid（DNA） strand breaks in Fe_2O_3-NPs treated groups.Cell cycle analysis revealed 88.4% of cells in sub-G1 apoptotic phase,suggesting cell death in Fe_2O_3-NPs（2.0 mg/m L） treated group.Taking together,the genotoxicity induced by Fe_2O_3-NPs highlights the importance of environmental risk associated with improper disposal of nanoparticles（NPs） and radish can serve as a good indicator for measuring the phytotoxicity of NPs grown in NP-polluted environment.

Monohalogenated acetamide-induced cellular stress and genotoxicity are related to electrophilic softness and thiol/thiolate reactivity

Haloacetamides（HAMs） are cytotoxic, genotoxic, and mutagenic byproducts of drinking water disinfection. They are soft electrophilic compounds that form covalent bonds with the free thiol/thiolate in cysteine residues through an S_N2 reaction mechanism.Toxicity of the monohalogenated HAMs（iodoacetamide, IAM; bromoacetamide, BAM;or chloroacetamide, CAM） varied depending on the halogen substituent. The aim of this research was to investigate how the halogen atom affects the reactivity and toxicological properties of HAMs, measured as induction of oxidative/electrophilic stress response and genotoxicity. Additionally, we wanted to determine how well in silico estimates of electrophilic softness matched thiol/thiolate reactivity and in vitro toxicological endpoints.Each of the HAMs significantly induced nuclear Rad51 accumulation and ARE signaling activity compared to a negative control. The rank order of effect was IAM 〉 BAM 〉 CAM for Rad51, and BAM ≈ IAM 〉 CAM for ARE. In general, electrophilic softness and in chemico thiol/thiolate reactivity provided a qualitative indicator of toxicity, as the softer electrophiles IAM and BAM were more thiol/thiolate reactive and were more toxic than CAM.

Theoretical and experimental study of surface texturing with laser machining

To explore the forming process and mechanism of the surface texture of laser micropits,this paper presents the thermal model of laser machining based on the Neumann boundary conditions and an investigation on the effects of various parameters on the processing.The surface profile and quality of the formed micropits were analyzed using NanoFocus 3D equipment through a design of experiment(DOE).The results showed that more intense melting and splashing occurred with higher power density and narrower pulse widths.Moreover,the compressive stress is an important indicator of the damage effects,and the circumferential thermal stress is the primary factor influencing the diameter expansion.During the process of laser machining,not only did oxides such as CuO and ZnO generate,the energy distribution also tended to decrease gradually from region#1 to region#3 based on an energy dispersive spectrometer(EDS)analysis.The factors significantly affecting the surface quality of the micropit surface texture are the energy and pulse width.The relationship between taper angle and energy is appropriately linear.Research on the formation process and mechanism of the surface texture of laser micropits provides important guidance for precision machining.

内质网应激蛋白在运动大鼠骨骼肌损伤中的表达变化

目的:研究内质网应激蛋白在运动大鼠骨骼肌损伤中的表达并探讨内质网应激在运动骨骼肌损伤中的保护作用。方法:雄性SD大鼠随机分成安静对照组(C)和单纯运动组(E),单纯运动组再平均分为运动即刻组(E1)、运动后24 h组(E2)、运动后48 h组(E3)和运动后6 d组(E4),每组8只,采用离心力竭运动为运动模式,实验后分别测定骨骼肌内质网应激蛋白表达以及血清中反应损伤特征的活性酶和抗氧化酶活性的变化。结果:运动后E1组SOD活性最高,与安静组相比并呈显著性差异(P<0.05);E2和E3组的SOD活性比安静时要低,其中与E2组呈显著性差异(P<0.05);运动后E2组MDA浓度最高,与安静对照组C比较,非常显著性差异(P<0.01),运动后E3组MDA浓度比E1、E2组低,并与E2组呈显著差异(P<0.05);血清CK、LDH在运动后24 h后达到峰值,其中E3组血清CK和LDH活性同安静对照组C比较,呈显著性差异(P<0.05),E1、E2组血清CK和LDH活性同安静对照组C比较,呈非常显著性(P<0.01);运动后E1、E2组骨骼肌中Grp78的表达的显著上升。结论:大鼠离心力竭运动后大鼠骨骼肌发生损伤,运动后骨骼肌内质网应激蛋白的发生是骨骼肌内质网应激一种体现,体现了对骨骼肌的保护。