分级加载与爆破扰动诱发声发射和微震活动的指数衰减规律

为了研究分级加载和采动爆破扰动引起的声发射和微震活动的衰减规律,提出一种新的指数衰减(ED)模型。结果表明:分级加载和爆破扰动后的微破裂活动衰减规律符合ED模型。模型中A与n之和表示初始微破裂事件数,n表示背景地震级别。ED模型可以描述初始微破裂事件的数量,其偏差小于10%。在本研究考虑的三种工况下,ED模型描述微破裂事件衰减规律的能力优于传统的余震模型。该模型可为矿山爆破时间间隔的选择提供参考,对保持金属矿山围岩的稳定性、保证安全生产具有重要意义。

Accuracy of multi-echo Dixon sequence in quantification of hepatic steatosis in Chinese children and adolescents

BACKGROUND Nonalcoholic fatty liver disease(NAFLD) is currently the outstanding cause of chronic liver disease in children and adolescents, especially in overweight and obese groups. Liver biopsy is the reference standard to diagnose NAFLD but invasive, thus it is not the best choice in clinical diagnosis and follow-up.Magnetic resonance(MR) is widely used in clinical trials to noninvasively quantify liver fat content in adults and children in foreign countries. While currently, it is rarely used in Chinese children and adolescents. We postulated that quantifying hepatic steatosis by MR could be extended to children and adolescents in China.AIM To investigate the accuracy of MR imaging(MRI) in quantifying liver fat with MR spectroscopy(MRS) as a reference. A secondary goal was to assess the prevalence of NAFLD in overweight and obese Chinese children and adolescents.METHODSThere were 86 children and adolescents enrolled in this study, including 65 overweight and obese children and 21 healthy children. The participants underwent MRI and MRS. MRI and MRS were performed using multi-echo Dixon and HISTO sequences, respectively, to calculate hepatic proton density fat fraction(PDFF). Hepatic steatosis was diagnosed using MRS-PDFF > 5% as the threshold. Spearman's analysis was used to evaluate the correlation between MRI and MRS. The agreement between these two methods was assessed by BlandAltman analysis.RESULTS The MRI-PDFF in the MRS region of interest and the entire liver was 9.9% ±10.3% with a range of 0.3%-39.9%, and 10.6% ± 9.4% with a range of 1.9%-38.9%,respectively. The MRS-PDFF was 9.1% ± 10.0%, with a range of 0.5%-37.8%. The incidence of hepatic steatosis detected by MRS-PDFF was 46.5%(40/86) of all participants, all of whom belonged to the overweight and obese group.Spearman's analysis indicated an excellent correlation between multi-echo Dixon and MRS(r > 0.9, P < 0.01). Bland-Altman analysis also demonstrated a good agreement between these two methods.CONCLUSION Multi-echo Dixon shows an excellent correlation and agreement with MRS in quantifying liver fat content and could be a potential tool to detect hepatic steatosis in Chinese children and adolescents.

Research progress of stem cells on glaucomatous optic nerve injury

Glaucoma, the second leading cause of blindness, is an irreversible optic neuropathy. The mechanism of optic nerve injury caused by glaucoma is undefined at present. There is no effective treatment method for the injury. Stem cells have the capacity of self-renewal and differentiation. These two features have made them become the research focus on improving the injury at present. This paper reviews the application progress on different types of stem cells therapy for optic nerve injury caused by glaucoma.

依达拉奉对矽肺大鼠的干预治疗作用研究

目的观察自由基清除剂依达拉奉(edaravone)对矽肺大鼠造模后肺纤维化的影响,探讨其对矽肺的治疗作用。方法 SPF级Wistar大鼠54只随机等分为9组:对照组,模型组以及依达拉奉干预组,后两组依采样时间分为7、14、21和28 d 4个亚组,每组各6只大鼠。除对照组外,其余各组大鼠采用非暴露法气管内一次性注射二氧化硅(Si O2)悬液(250 mg/kg)复制矽肺动物模型;依达拉奉组自注射Si O2后每天腹腔注射依达拉奉(4 ml/kg),对照组每天用生理盐水腹腔注射(4 ml/kg),连续28 d。采用HE染色技术观察各组大鼠肺组织形态学变化,Western blot检测肺组织中转化生长因子β(TGF-β)蛋白的表达;试剂盒检测肺组织中羟脯氨酸(HYP)、还原型谷胱甘肽(GSH)和丙二醛(MDA)含量。结果依达拉奉可改善矽肺大鼠肺间质纤维化程度,提高矽肺大鼠肺组织匀浆GSH活力,降低HYP、TGF-β和MDA含量。结论依达拉奉可降低大鼠体内自由基及TGF-β水平,对矽肺大鼠有较好的治疗作用。

Genome and population evolution and environmental adaptation of Glyptosternon maculatum on the Qinghai-Tibet Plateau

Persistent uplift means the Qinghai-Tibet Plateau(QTP)is an ideal natural laboratory to investigate genome evolution and adaptation within highland environments.However,how paleogeographic and paleoclimatic events influence the genome and population of endemic fish species remains unclear.Glyptosternon maculatum is an ancient endemic fish found on the QTP and the only critically endangered species in the Sisoridae family.Here,we found that major transposons in the G.maculatum genome showed episodic bursts,consistent with contemporaneous geological and climatic events during the QTP formation.Notably,histone genes showed significant expansion in the G.maculatum genome,which may be mediated by long interspersed nuclear elements(LINE)repetitive element duplications.Population analysis showed that ancestral G.maculatum populations experienced two significant depressions 2.6 million years ago(Mya)and 10000 years ago,exhibiting excellent synchronization with Quaternary glaciation and the Younger Dryas,respectively.Thus,we propose that paleogeography and paleoclimate were dominating driving forces for population dynamics in endemic fish on the QTP.Tectonic movements and temperature fluctuation likely destroyed the habitat and disrupted the drainage connectivity among populations.These factors may have caused severe bottlenecks and limited migration among ancestral G.maculatum populations,resulting in the low genetic diversity and endangered status of the species today.

Clinical epidemiological study on intrahepatic cholelithiasis: analysis of 8585 cases

OBJECTIVE: To investigate the clinical epidemiology of intrahepatic cholelithiasis in Guangxi area, China. METHODS: 8585 cases of cholelithiasis proved by surgery in a period of 19 years were analyzed retrospectively. Data were collected and analyzed by computer software package PEMS. RESULTS: Cases of intrahepatic cholelithiasis accounted for more than one third of cases of cholelithiasis treated in the same period. The prevalence of intrahepatic cholelithiasis in farmers increased from 23.4% out of all cases with gallstone in 1981-1985 to 55.8% in 1991-1999. The constituent ratio of intrahepatic cholelithiasis in males was nearly the same in females. The peak prevalence age of patients with intrahepatic cholelithiasis ranged from 31 to 40 years, and the mortality was the highest among all bile stone cases. CONCLUSION: Intrahepatic cholelithiasis is by no means a vanishing disease, especially in rural area.

Effect on changes of blood coagulation function, cytokines and immune function in patients undergoing laparoscopic radical gastrectomy for gastric cancer

Objective:To explore the changes of coagulation function, cytokines and T lymphocyte in patients undergoing laparoscopic radical gastrectomy for gastric cancer and its clinical significance.Methods: 40 cases of laparoscopic radical gastrectomy for gastric cancer patients and 40 cases of open radical gastrectomy for gastric cancer patients in our hospital were selected to detect and investigate the perioperative coagulation function [APTT (activated partial thromboplastin time), FIB (fibrinogen), and PLT (platelet)], cytokines [CRP (C reactive protein), IL-6 (IL-6) and TNF-alpha (Tumor necrosis factor-alpha)] and T lymphocytes (CD4+, CD8+ and CD4+/CD8+) changes and clinical meaning of patients in the two groups.Results: The coagulation function related indicators, cytokines and T lymphocytes of the two groups before treatment did not change significantly (P>0.05). 1 d after operation, blood coagulation, TNF-alpha, CD4+ and CD4+/CD8+ levels were significantly lower than that before operation in two groups of patients (P<0.05), while IL-6, CRP and CD8+ were significantly higher than that before the operation (P<0.05), and the index change in open group was more obvious. 3 d after surgery, the APTT, IL-6, CRP, CD4+, CD8+ and PLT levels in two group patients were significantly lower than that 1 d after surgery, while FIB, TNF-alpha and CD4+/CD8+ were significantly higher than that 1 d after surgery;blood coagulation index, TNF-alpha and CD4+ and CD4+/CD8+ were significantly lower in the laparotomy group patients than in laparoscopic group, while IL-6, CRP and CD8+ were significantly higher than the laparoscopic group (P<0.05). 5 d after operation, the APTT, TNF-alpha, FIB, CD4+, CD4+/CD8+ and PLT in two groups were significantly higher than that 3 d after surgery (P<0.05), while IL-6, CRP and CD8+ levels were significantly lower than that of 3 d after surgery (P<0.05);blood coagulation index, TNF-alpha and CD4+ and CD4+/CD8+ in the laparotomy group patients were significantly lower than laparoscopic group (P<0.05), while IL-6, CRP and CD8+ were significantly higher than the laparoscopic group (P<0.05).Conclusions: Radical resection of gastric cancer can cause coagulation disorder, inhibit the immune function and inflammatory reaction, and gradually recover with the passage of time;Compared with open surgery, laparoscopic radical gastrectomy have smaller impact on patients and recovery faster.

Effect on T cell subsets and function of isletβ cells of levemir combined with acarbose in elder patients with early-onset type 2 Diabetes Mellitus

Objective:To discuss the effect of the combined therapy of levemir and acarbose on T cell subsets and function of isletβ cells in elder patients with early-onset type 2 Diabetes Mellitus. Methods:According to the number parity of entry sequence, 100 cases of elder patients with early-onset type 2 Diabetes Mellitus are divided into the control group and the observation group of 50 cases. The control group was treated with novolin and acarbose, the observation group was given subcutaneous injection of levemir and acarbose treatment. Compare the T cell subsets and function of isletβ cells in two group of patients before the treatment (T0), treatment for 4 weeks (T1) ,treatment for 8 weeks (T2).Results:(1) The levels of T0, T1, T2CD3+, CD4+, CD4+/CD8+ were increased in both groups, and CD8+ decreased. Among them, the levels of T1, T2CD3+, CD4+, CD4+/CD8+ of the observation group were obviously higher than the control group, the level of CD8+ was lowly than the control group, the difference was statistically significant;(2) In the stage of T0, T1, T2, the levels of FPG, HbA1c, HOMA-IR were showed a downward trend, the levels of FIns, HOMA-B were increased. In these two groups, the levels of T1, T2FPG, HbA1c, HOMA-IR of the observation group were lower than the control group, and the levels of FIns, HOMA-B were higher than the control group, the difference was statistically significant;(3) In the control group occurred 3 cases of hypoglycemia, and the incidence of adverse reactions was 6%. However, in the observation group no occurred adverse reactions, the difference was statistically significant.Conclusions:The combined therapy of levemir and acarbose in elder patients with early-onset type 2 Diabetes Mellitus, It helps to improve immune function, protect the isletβ-cell function.

Effects of two silicone resin coatings on performance of FeSiAl magnetic powder cores

Two silicon resins with excellent thermal stability,JH1123 and JH7102,are used as the insulated agents and binders for the gas-atomized FeSiAl powder,and corresponding magnetic powder cores(MPCs)are fabricated.The insulation capability and application prospects of the two silicon resins are evaluated by comparing the magnetic properties of the coated powder and MPCs.The scanning electron microscopy,energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy results show that uniform insulation layers are both formed on the powder surfaces.JH1123 has stronger binding ability,and the JH1123-coated powder exhibits severe agglomeration,with d50(average particle size)approximately twice that of the JH7102-coated powder.Both as-prepared MPCs exhibit outstanding soft magnetic properties.Wherein,the permeability of FeSiAl@JH1123 is up to 74.0,which is 35.5%higher than that of FeSiAl@JH7102 because JH1123 can further improve the density of the MPCs.As for FeSiAl@JH7102,it has better direct current bias and lower core loss of 716.9 mW cm^(−3) at 20 mT and 1000 kHz due to its lower coercivity and greater anti-magnetic saturation ability.A comprehensive comparison shows that FeSiAl@JH1123 is suitable for medium and high frequency applications,while FeSiAl@JH7102 is more suitable for high frequency applications.This indicates that the use of JH1123 and JH7102 silicon resins for binding and insulated coating not only simplifies the preparation process of MPCs,but also enables the controlled production of MPCs for different applications.

Simulation and experiment investigations on fabrication of Fe-based amorphous powders by a novel atomization process equipped with assisted gas nozzles

Based on computational fluid dynamics method,the effect of atomization gas pressure on the atomization efficiency of Laval nozzle was studied,and then a discrete phase model was established and combined with industrial trials to study the effect of a new type of assisted gas nozzles(AGNs)on powder size distribution and amorphous powder yield.The results show that increasing the atomization pressure can effectively improve the gas velocity for the Laval nozzle;however,it will decrease the aspiration pressure,and the optimal atomization pressure is 2.0 MPa.Compared with this,after the application of AGNs with the inlet velocity of 200 m s^(-1),assisted gas jet can increase the velocity of overall droplets in the break-up and solidification area by 40 m s^(-1) and the maximum cooling rate is increased from 1.9×10^(4) to 2.3×10^(4) K s^(-1).The predicted particle behavior is demonstrated by the industrial trails,that is,after the application of AGNs,the median diameter of powders d50 is decreased from 28.42 to 25.56 lm,the sphericity is increased from 0.874 to 0.927,the fraction of amorphous powders is increased from 90.4% to 99.4%,and only the coercivity is increased slightly due to the accumulation of internal stress.It is illustrated that the AGNs can improve the yield of fine amorphous powders,which is beneficial to providing high-performance raw powders for additive manufacturing technology.

Experimental and numerical investigations of the collapse of a laser-induced cavitation bubble near a solid wall

With the collapse of cavitation bubbles near the wall,micro-jets and shock waves will be formed,to generate a high-pressure load and to cause the cavitation damage on the surface of the hydraulic machinery.Due to the rapid development of the cavitation bubble collapse process(in the time scale of hundred nanoseconds),the time resolution of the conventional high-speed cameras should reach more than one million frames per second,which will limit the spatial resolution,and obscure the details of the cavitation bubble shape near the cavitation bubble collapse moment.In this paper,with the help of the laser cavitation bubble photogrammetry system with nanosecond-micron space-time resolution,the experiment is carried out for the cavitation bubble collapse morphology evolution near the wall.The morphological characteristics of the cavitation bubble collapse at specific times are analyzed.With the help of the OpenFOAM code,the collapse process of the cavitation bubble near the solid wall is calculated.It is shown that the cavitation bubble near the wall collapses in an axial symmetric heart shape and the micro-jet directed to the wall will pull the cavitation bubble towards the wall.The counter-jet generated in the rebound stage will drive the cavitation bubble to move away from the wall.The numerical simulation of the cavitation bubble shape in the collapse period is well consistent with the experimental results,but the ability to capture the shock wavefront needs to be improved.Under the conditions studied in this paper,the cavitation bubble collapse micro-jet velocity can reach up to a hundred meters per second both in the experiment and the numerical simulation.

HSH-carbon: A novel sp^(2)–sp^(3) carbon allotrope with an ultrawide energy gap

An sp^(2)-sp^(3) hybrid carbon allotrope named HSH-carbon is proposed by the first-principles calculations.The structure of HSH-carbon can be regarded as a template polymerization of[1.1.1]propellane molecules in a hexagonal lattice,as well as,an AA stacking of recently reported HSH-C10 consisting of carbon trigonal bipyramids.Based on calculations,the stability of this structure is demonstrated in terms of the cohesive energy,phonon dispersion,Born–Huang stability criteria,and ab initio molecular dynamics.HSHcarbon is predicted to be a semiconductor with an indirect energy gap of 3.56 eV at the PBE level or 4.80 eV at the HSE06 level.It is larger than the gap of Si and close to the gap of c-diamond,which indicates HSH-carbon is potentially an ultrawide bandgap semiconductor.The effective masses of carriers in the VB and CB edge are comparable with wide bandgap semiconductors such as GaN and ZnO.The elastic behavior of HSH-carbon such as bulk modulus,Young’s modulus and shear modulus is comparable with that of T-carbon and much smaller than that of c-diamond,which suggests that HSH-carbon would be much easier to be processed than c-diamond in practice.