A state‑of‑the‑art review on rock seepage mechanism of water inrush disaster in coal mines

Water inrush is one of the most dangerous disasters in coal mining.Due to the large-scale mining and complicated hydrogeological conditions,thousands of deaths and huge economic losses have been caused by water inrush disasters in China.There are two main factors determining the occurrence of water inrush:water source and water-conducting pathway.Research on the formation mechanism of the water-conducting pathway is the main direction to prevent and control the water inrush,and the seepage mechanism of rock mass during the formation of the water-conducting pathway is the key for the research on the water inrush mechanism.This paper provides a state-of-the-art review of seepage mechanisms during water inrush from three aspects,i.e.,mechanisms of stress-seepage coupling,fow regime transformation and rock erosion.Through numerical methods and experimental analysis,the evolution law of stress and seepage felds in the process of water inrush is fully studied;the fuid movement characteristics under diferent fow regimes are clearly summarized;the law of particle initiation and migration in the process of water inrush is explored,and the efect of rock erosion on hydraulic and mechanical properties of the rock media is also studied.Finally,some limitations of current research are analyzed,and the suggestions for future research on water inrush are proposed in this review.

A Numerical Gas Fracturing Model of Coupled Thermal,Flowing and Mechanical Effects

Gas fracturing,which overcomes the limitation of hydraulic fracturing,is a potential alternative technology for the development of unconventional gas and oil resources.However,the mechanical principle of gas fracturing has not been learned comprehensively when the fluid is injected into the borehole.In this paper,a damage-based model of coupled thermal-flowing-mechanical effects was adopted to illustrate the mechanical principle of gas fracturing.Numerical simulation tools Comsol Multiphysics and Matlab were integrated to simulate the coupled process during the gas fracturing.Besides,the damage evolution of drilling areas under several conditions was fully analyzed.Simulation results indicate that the maximum tensile stress,which occurs in the upper and lower of the injection hole,decreases with the increase of the tectonic stress coefficient(TSC).As the TSC increases,shear fractures increase,a crushed area is gradually formed and the seepage area increases rapidly.The influence of TSC on fracture expansion is concluded as follows:with the decrease of TSC,the relative width of fractures decreases whilst the depth increases.It indicates that thermal stress and pore pressure promote the expansion of tensile fractures but restrain the expansion of shear fractures.Therefore,a relatively lower injection gas pressure is required to obtain the same degree of fracturing with a coupled thermal gradient.

Glacier changes in the Qaidam Basin from 1977 to 2018

Based on Landsat MSS/TM/OLI remote sensing images,glaciers vector data in the Qaidam Basin were extracted for 1977,2002,and 2018,and their spatial-temporal variations were analyzed.Results show that there were 2,050 glaciers covering an area of 1,693.54±40.96 km2 and having an ice volume of 108.65±2.43 km^3 in the Qaidam Basin in 2018.Glaciers with areas<1.0 km2 accounted for the largest number,while glaciers with areas of 1.0−5.0 km2 accounted for the most glacierized area.In the past 50 years,the number of glaciers decreased by 177,and the glacier area and volume reduced by 338.08 km2(−8.12 km^2/a)and 19.92 km3(−0.48 km^3/a),respectively.Retreat altitudes of glaciers were concentrated at 4,900−5,600 m,4,700−5,200 m,and 5,000−5,600 m and reduced areas accounted for 95.53%,77.80%,and 69.19%in the Kunlun,Qilian,and Altun mountains,respectively.The area of north-oriented glaciers decreased the most(−125.43 km^2),but the west-and east-oriented glaciers retreated at the fastest rate(i.e.,−27.11%and−27.10%).All glaciers showed a decreasing trend in sub-regions of the Qaidam Basin from 1977 to 2018.The decreasing trend was accelerated gradually from northwest to southeast in the northern part of the basin,while glacier change was the smallest in the middle section and gradually accelerated towards both ends of the basin's southern part.The temperature had continued to rise,and the precipitation had increased slowly in the Qaidam Basin during the past 50 years.The continuous rise in air temperature was the main reason for the retreat of glaciers.

玉米秸秆木聚糖的硫酸化修饰及抗氧化活性研究

以玉米秸秆为原料采用碱提醇沉法提取木聚糖,通过筛选合适的酯化体系(ClSO_(3)H/C_(5)H_(5)N法、C_(5)H_(5)N·SO_(3)/C_(5)H_(5)N法、氨基三磺酸钠法)制备了玉米秸秆木聚糖硫酸酯,产物结构特征经IR、^(13)C NMR确证,进一步考察了其抗氧化活性。通过碱提醇沉法获得木聚糖,经氨基三磺酸钠法酯化体系(反应时间2.5 h,反应温度45℃),所获得的产物硫酸取代度(DS)为1.566。体外抗氧化实验表明,玉米秸秆木聚糖硫酸酯对·OH有较好的清除能力,具有剂量依赖性,并且硫酸酯化可以提高玉米秸秆木聚糖的抗氧化活性。

Effects of intracoronary arterial injection of tirofiban on no-reflow phenomenon in patients with acute ST-segment elevation myocardial infarction underwent primary percutaneous coronary intervention

Objective: To compare the effect of intracoronary arterial injection of tirofiban and sodium nitroprusside (SNP) on no-reflow phenomenon in patients with acute ST-segment elevation myocardial infarction (STEMI) underwent primary percutaneous coro-nary intervention (PCI). Methods: A total of 68 patients with acute STEMI who had no-reflow phenomenon during PCI were chosen and randomly divided into SNP group (n = 34) and tirofiban group (n = 34). Aiming at no-reflow phenomenon during PCI, with the use of microcatheters, intracoronary arterial injection of tirofiban was given in tirofiban group, while intracoronary bolus of SNP was given in SNP group. Coronary angiography was conducted to record TIMI flow grade of the infarct-related artery after 10 minutes. Plasma brain natriuretic peptide (BNP) was monitored before and after PCI (in 24 hours). With the help of ultrasound cardiogram, left ventricular ejection fraction (LVEF), left ventricular end-diastolic dimension (LVEDD) and left ventricular end-systolic dimension (LVESD) were recorded and compared in 30 days after PCI. Results: The ratio of TIMI grade 3 blood flow in tirofiban group was significantly higher than that in SNP group (76.5% (26/34) vs. 52.9% (18/34), p = .03)BNP levels in two groups had no statistical significance before PCI (p = .16), but in 24 h after PCI, BNP levels in tirofiban group were significantly lower than those in SNP group ((439.00 ± 4.90) μmol/L vs. (632.00 ± 3.63) μmol/L, p = .02)In 30 days after PCI, LVEF, LVEDD and LVESD in tirofiban group were all superior to those in SNP group (all p < .05). Conclusions: Intracoronary arterial injection of tirofiban was superior to SNP in improving no-reflow phenomenon in STEMI patients after PCI in the emergency treatment. Tirofiban therapy can increase coronary blood flow and myocardial perfusion after the occurrence of no-reflow phenomenon during PCI in STEMI patients, and improve long-term prognosis.

2018 Chinese Pediatric Cardiology Society(CPCS) guideline for diagnosis and treatment of syncope in children and adolescents

Syncope belongs to the transient loss of consciousness(TLOC), characterized by a rapid onset, short duration, and spontaneous complete recovery. It is common in children and adolescents, accounting for 1% to 2% of emergency department visits.Recurrent syncope can seriously affect children's physical and mental health, learning ability and quality of life and sometimes cardiac syncope even poses a risk of sudden death. The present guideline for the diagnosis and treatment of syncope in children and adolescents was developed for guiding a better clinical management of pediatric syncope. Based on the globally recent development and the evidence-based data in China, 2018 Chinese Pediatric Cardiology Society(CPCS) guideline for diagnosis and treatment of syncope in children and adolescents was jointly prepared by the Pediatric Cardiology Society, Chinese Pediatric Society, Chinese Medical Association(CMA)/Committee on Pediatric Syncope, Pediatricians Branch, Chinese Medical Doctor Association(CMDA)/Committee on Pediatric Cardiology, Chinese College of Cardiovascular Physicians, Chinese Medical Doctor Association(CMDA)/Pediatric Cardiology Society, Beijing Pediatric Society, Beijing Medical Association(BMA). The present guideline includes the underlying diseases of syncope in children and adolescents, the diagnostic procedures, methodology and clinical significance of standing test and headup tilt test, the clinical diagnosis vasovagal syncope, postural orthostatic tachycardia syndrome, orthostatic hypotension and orthostatic hypertension, and the treatment of syncope as well as follow-up.

Screening of novel synthetic derivatives of dehydroepiandrosterone for antivirals against flaviviruses infections

Flaviviruses are important arthropod-borne pathogens that represent an immense global health problem.Their unprecedented epidemic rate and unpredictable clinical features underscore an urgent need for antiviral interventions.Dehydroepiandrosterone(DHEA)is a natural occurring adrenal-derived steroid in the human body that has been associated in protection against various infections.In the present study,the plaque assay based primary screening was conducted on 32 synthetic derivatives of DHEA against Japanese encephalitis virus(JEV)to identify potent anti-flaviviral compounds.Based on primary screening,HAAS-AV3026 and HAAS-AV3027 were selected as hits from DHEA derivatives that exhibited strong antiviral activity against JEV(IC_(50)=2.13 and 1.98μmol/L,respectively)and Zika virus(ZIKV)(IC_(50)=3.73 and 3.42μmol/L,respectively).Mechanism study indicates that HAAS-AV3026 and HAAS-AV3027 do not exhibit inhibitory effect on flavivirus binding and entry process,while significantly inhibit flavivirus infection at the replication stage.Moreover,indirect immunofluorescence assay,Western blot analyses,and quantitative reverse transcription-PCR(qRT-PCR)revealed a potent antiviral activity of DHEA derivatives hits against JEV and ZIKV in terms of inhibition of viral infection,protein production,and viral RNA synthesis in Vero cells.Taken together,our results may provide a basis for the development of new antivirals against flaviviruses.

Malignant transformation and treatment of cystic mixed germ cell tumor

Objective:The authors report an extremely unusual presentation and management of a children pineal mixed germ cell tumor mainly composed of immature teratoma,aiming to summarize main theraptic points by literature review.Methods:A cystic lesion located in the rear of third ventricle in a child was detected3 years ago with no other therapy performed except for a ventriculo-peritoneal shunt.During the following 3 years,intermitted regular brain MRI demonstrated no evidence of lesion aggrandizement.However from 20 days before admission to our institute the patient began to present acutely with exacerbating clinical symptoms meanwhile brain MRI showed signs of abrupt revulsions of initial lesion without any incentive cause.Neurological examination revealed a significant rising of serum tumor marker level.Then surgical resection was performed immediately after admission which was followed by correlative two-course chemotherapy.Results:Postoperative brain MRI demonstrated totally removing of the lesion in rear of third ventricle.Serum tumor marker level decreased remarkably after surgery and declined to normal level after two-course chemotherapy.No obvious neurological deficit occurred except for short-term memory difficulty which gradually recovered within two weeks.Soon after the second course chemotherapy the patient was currently asymptomatic and returned to school.Conclusions:(1)To ensure definitive diagnosis and proper therapecutic protocols benefit from grasping clinical features of mixed germ cell tumor.(2)Overall preoperative investigation including serum tumor marker level is as critical as neurological imaging examination.(3)Surgical excision is confirmed to be the key modality of treatment.With the regarding of mixed germ cell tumor,never highlight total resection too much.(4)Postoperative adjuvant chemotherapy is recommended as further intensive treatment to improve the prognosis of mix germ cell tumor.