Cumulative effects of excess high-normal alanine aminotransferase levels in relation to new-onset metabolic dysfunction-associated fatty liver disease in China

BACKGROUND Within the normal range,elevated alanine aminotransferase(ALT)levels are associated with an increased risk of metabolic dysfunction-associated fatty liver disease(MAFLD).AIM To investigate the associations between repeated high-normal ALT measurements and the risk of new-onset MAFLD prospectively.METHODS A cohort of 3553 participants followed for four consecutive health examinations over 4 years was selected.The incidence rate,cumulative times,and equally and unequally weighted cumulative effects of excess high-normal ALT levels(ehALT)were measured.Cox proportional hazards regression was used to analyse the association between the cumulative effects of ehALT and the risk of new-onset MAFLD.RESULTS A total of 83.13%of participants with MAFLD had normal ALT levels.The incidence rate of MAFLD showed a linear increasing trend in the cumulative ehALT group.Compared with those in the low-normal ALT group,the multivariate adjusted hazard ratios of the equally and unequally weighted cumulative effects of ehALT were 1.651[95%confidence interval(CI):1.199-2.273]and 1.535(95%CI:1.119-2.106)in the third quartile and 1.616(95%CI:1.162-2.246)and 1.580(95%CI:1.155-2.162)in the fourth quartile,respectively.CONCLUSION Most participants with MAFLD had normal ALT levels.Long-term high-normal ALT levels were associated with a cumulative increased risk of new-onset MAFLD.

Study on cumulative effects of biological craniocerebral trauma under repeated blast

Repeated blast impacts on personnel in explosive environments can exacerbate craniocerebral trauma.Most existing studies focus on the injury effects of a single blast,lacking in-depth analysis on the injury effects and cumulative effects of repeated blasts.Therefore,rats were used as the experimental samples to suffer from explosion blasts with different peak air overpressures(167 kPa~482 kPa)and varying number of repeated blasts.The cumulative effect of craniocerebral trauma was most pronounced for moderate repeated blast,showing approximately 95%increase of trauma severity with penta blast,and an approximately 85%increase of trauma severity with penta minor blast.The cumulative effect of craniocerebral trauma from severe,repeated blast has a smaller rate of change compared to the other two conditions.The severity of trauma from penta blast increased by approximately 69%compared to a single blast.Comprehensive physiological,pathological and biochemical analysis show that the degree of neurological trauma caused by repeated blasts is higher than that of single blasts,and the pathological trauma to brain tissue is more extensive and severe.The trauma degree remains unchanged after double blast,increases by one grade after triple or quadruple blast,and increases by two grades after penta blast.

Seasonal Cumulative Effect of Ural Blocking Episodes on the Frequent Cold events in China during the Early Winter of 2020/21

Starting in mid-November,China was hit by several cold events during the early winter of 2020/21.The lowest temperature observed at Beijing station on 7 January reached−19.6°C.In this paper,we show that the outbreak of the record-breaking extreme cold event can be attributed to a huge merging Ural blocking(UB)ridge over the Eurasian region.The sea-ice cover in the Kara and East Siberia Seas(KESS)in autumn was at its lowest value since 1979,which could have served as a precursor signal.Further analysis shows that several successive UB episodes occurred from 1 September 2020 to 10 January 2021.The persistent UB that occurred in late September/early October 2020 may have made an important contribution to the October historical minimum of sea ice in the KESS region.Our results also show that,after each UB episode in winter,significant upward propagation of wave activity occurred around 60°E,which resulted in weakening the stratospheric vortex.Meanwhile,each UB episode also caused a significant reduction in sea-ice extent in KESS and a significant weakening of the westerly jet in mid-high-latitude Eurasia.Results suggest that the Arctic vortex,which is supposed to enhance seasonally,became weaker and more unstable than the climatic mean under the seasonal cumulative effects of UB episodes,KESS warming,and long-lasting negative-phase North Atlantic Oscillation(NAO-).Those seasonal cumulative effects,combined with the impact of La Niña winter,led to the frequent occurrence of extreme cold events.

Quantitative Evaluation of Ecological Cumulative Effects and Zoning Regulations for Prefectural Mining Units in China

Although the development of energy and mineral resources strongly supports China’s rapid industrialization and urbanization,it has led to a series of ecological and environmental problems.Strengthening the spatial regulation considering the ecological and environmental protection on energy and mineral resource development areas is an important aspect of realizing China’s sustainable development.In this study,we mapped,categorized,and analyzed the ecological cumulative effects of the Chinese 134 prefectural mining units based on the pressure-state-response model,which is demonstrated as impact of mining activities on ecological environment,ecological environmental fragility,and ecological function.This investigation developed a stress zoning typology of the mining units based on scores of three dimensions of the ecological cumulative effects and classified 134 prefectural mining units into eight types of stress zones.A series of regulation and policy suggestions have been proposed to different types of zones from three aspects:space control,intensity control,and development mode control.The application of this evaluation and spatial zoning system will contribute to the refined spatial management of China’s mining areas.

Time-lagged and cumulative effects of drought and anthropogenic activities on China's vegetation greening from 1990 to 2018

Previous studies have confirmed the time-lagged and cumulative effects of drought and anthropogenic activities on vegetation growth,but these studies focus on the time-lagged effect of drought and are poorly known how vegetation productivity responds to anthropogenic activities.Here,based on the reconstructed Normalized Difference Vegetation Index,the Standardized Precipitation Evapotranspiration Index and land use degree comprehensive index,we diagnosed the spatiotemporal pattern of vegetation and drought,investigated time-lagged and cumulative effects of drought and anthropogenic activities over China through the month where the maximum correlation coefficient occurred.It revealed that the browning trend of 32.21%of vegetated lands was covered by overall greening,especially northwestern China.Drought intensified with a rate of 0.0014/year.in 66.41%and 54.57%of the vegetated lands had time-lagged and cumulative response to drought,with a shorter timescales of 1–4 months,indicating the higher sensitivity of vegetation growth to drought.There was a U-shaped relationship between moisture conditions and vegetation response time.49.9%of China’s vegetation showed time-lagged effects to anthropogenic activities,with a longer timescales of 6–10 years,demonstrating that anthropogenic activities triggered ecological changes but vegetation ecosystems cannot keep pace.The accumulated and time-lagged years declined with increased land use intensity.

Correlation between the cumulative analgesic effect of electroacupuncture intervention and synaptic plasticity of hypothalamic paraventricular nucleus neurons in rats with sciatica

In the present study, a rat model of chronic neuropathic pain was established by ligation of the sciatic nerve and a model of learning and memory impairment was established by ovariectomy to investigate the analgesic effect of repeated electroacupuncture stimulation at bilateral Zusanfi （ST36） and Yanglingquan （GB34）. In addition, associated synaptic changes in neurons in the paraventricular nucleus of the hypothalamus were examined. Results indicate that the thermal pain threshold （paw withdrawal latency） was significantly increased in rats subjected to 2-week electroacupuncture intervention compared with 2-day electroacupuncture, but the analgesic effect was weakened remarkably in ovariectomized rats with chronic constrictive injury. 2-week electroacupuncture intervention substantially reversed the chronic constrictive injury-induced increase in the synaptic cleft width and thinning of the postsynaptic density. These findings indicate that repeated electroacupuncture at bilateral Zusanfi and Yanglingquan has a cumulative analgesic effect and can effectively relieve chronic neuropathic pain by remodeling the synaptic structure of the hypothalamic paraventricular nucleus.

The cumulative analgesic effect of repeated electroacupuncture involves synaptic remodeling in the hippocampal CA3 region

In the present study, we examined the analgesic effect of repeated electroacupuncture at bilateral Zusanfi （ST36） and Yanglingquan （GB34） once a day for 14 consecutive days in a rat model of chronic sciatic nerve constriction injury-induced neuropathic pain. In addition, concomitant changes in calcium/calmodulin-dependent protein kinase II expression and synaptic ultrastructure of neurons in the hippocampal CA3 region were examined. The thermal pain threshold （paw withdrawal latency） was increased significantly in both groups at 2 weeks after electroacupuncture intervention compared with 2 days of electroacupuncture. In ovariectomized rats with chronic constriction injury, the analgesic effect was significantly reduced. Electroacupuncture for 2 weeks significantly diminished the injury-induced increase in synaptJc cleft width and thinning of the postsynaptJc density, and it significantly suppressed the down-regulation of intracellular calcium/ calmodulin-dependent protein kinase II expression in the hippocampal CA3 region. Repeated electroacupuncture intervention had a cumulative analgesic effect on injury-induced neuropathic pain reactions, and it led to synaptic remodeling of hippocampal neurons and upregulated calcium/calmodulin-dependent protein kJnase II expression in the hippocampal CA3 region.

Analytic Mechanism for the Cumulative Effect of Wind Power Fluctuations from Single Wind Farm to Wind Farm Cluster

The use of wind power is rapidly growing worldwide as a means of reducing carbon emissions for the energy sector.China has the world’s largest wind power installation and multiple large-scale wind farm clusters,each comprising dozens of wind farms.For the planning and operation of the power system,it is important to understand the power fluctuation characteristics of wind farm clusters.Several studies demonstrate that the relative power fluctuation of a wind farm cluster is less than that of a single wind farm.Is this decreasing trend a random occurrence or does it have a regular pattern?This scientific question is addressed by investigating the mechanism of the cumulative effect of a wind farm cluster.In this study,a cumulative model is proposed by examining the spatiotemporal relationships of wind power variations and wind farm dispersion.Structural gain function and critical cumulative frequency are defined as the foundations to analytically describing the cumulative effect.By investigating the cumulative effect mechanism,the relationship between power fluctuation and spatiotemporal parameters of the wind farm cluster are revealed.The power fluctuation of a cluster can be predicted using the cumulative model even before it is completely built.The mechanism of the cumulative effect is validated on the basis of the data of two actual wind farm clusters.

Blasting cumulative damage effects of underground engineering rock mass based on sonic wave measurement

The principle of sonic wave measurement was introduced, and cumulative damage effects of underground engineering rock mass under blasting load were studied by in situ test, using RSM-SY5 intelligent sonic wave apparatus. The blasting test was carried out for ten times at some tunnels of Changba Lead-Zinc Mine. The damage depth of surrounding rock caused by old blasting excavation （0.8-1.2 m） was confirmed. The relation between the cumulative damage degree and blast times was obtained. The results show that the sonic velocity decreases gradually with increasing blast times, hut the damage degree （D） increases. The damage cumulative law is non-linear. The damage degree caused by blast decreases with increasing distance, and damage effects become indistinct. The blasting damage of rock mass is anisotropic. The damage degree of rock mass within charging range is maximal. And the more the charge is, the more severe the damage degree of rock mass is. The test results provide references for researches of mechanical parameters of rock mass and dynamic stability analysis of underground chambers.

Shaking table test and cumulative deformation evaluation analysis of a tunnel across the hauling sliding surface

To explore the cumulative deformation effect of the dynamic response of a tunnel crossing the hauling sliding surface under earthquakes,the shaking table test was conducted in this study.Combined with the numerical calculations,this study proposed magnification of the Arias intensity(MIa)to characterize the overall local deformation damage of the tunnel lining in terms of the deformation characteristics,frequency domain,and energy.Using the time‐domain analysis method,the plastic effect coefficient(PEC)was proposed to characterize the degree of plastic deformation,and the applicability of the seismic cumulative failure effect(SCFE)was discussed.The results show that the low‐frequency component(f1 and f2≤10 Hz)and the high‐frequency component(f3 and f4>10 Hz)acceleration mainly cause global and local deformation of the tunnel lining.The local deformation caused by the high‐frequency wave has an important effect on the seismic damage of the lining.The physical meaning of PEC is more clearly defined than that of the residual strain,and the SCFE of the tunnel lining can also be defined.The SCFE of the tunnel lining includes the elastic deformation effect stage(<0.15g),the elastic–plastic deformation effect stage(0.15g–0.30g),and the plastic deformation effect stage(0.30g–0.40g).This study can provide valuable theoretical and technical support for the construction of traffic tunnels in high‐intensity earthquake areas.

Spatiotemporal changes of gross primary productivity and its response to drought in the Mongolian Plateau under climate change

Gross primary productivity(GPP)of vegetation is an important constituent of the terrestrial carbon sinks and is significantly influenced by drought.Understanding the impact of droughts on different types of vegetation GPP provides insight into the spatiotemporal variation of terrestrial carbon sinks,aiding efforts to mitigate the detrimental effects of climate change.In this study,we utilized the precipitation and temperature data from the Climatic Research Unit,the standardized precipitation evapotranspiration index(SPEI),the standardized precipitation index(SPI),and the simulated vegetation GPP using the eddy covariance-light use efficiency(EC-LUE)model to analyze the spatiotemporal change of GPP and its response to different drought indices in the Mongolian Plateau during 1982-2018.The main findings indicated that vegetation GPP decreased in 50.53% of the plateau,mainly in its northern and northeastern parts,while it increased in the remaining 49.47%area.Specifically,meadow steppe(78.92%)and deciduous forest(79.46%)witnessed a significant decrease in vegetation GPP,while alpine steppe(75.08%),cropland(76.27%),and sandy vegetation(87.88%)recovered well.Warming aridification areas accounted for 71.39% of the affected areas,while 28.53% of the areas underwent severe aridification,mainly located in the south and central regions.Notably,the warming aridification areas of desert steppe(92.68%)and sandy vegetation(90.24%)were significant.Climate warming was found to amplify the sensitivity of coniferous forest,deciduous forest,meadow steppe,and alpine steppe GPP to drought.Additionally,the drought sensitivity of vegetation GPP in the Mongolian Plateau gradually decreased as altitude increased.The cumulative effect of drought on vegetation GPP persisted for 3.00-8.00 months.The findings of this study will improve the understanding of how drought influences vegetation in arid and semi-arid areas.

Acupuncture effects on the hippocampal cholinergic system in a rat model of neuropathic pain

The present study observed the effects of repeated electroacupuncture of Zusanli （ST36） and Yanglingquan （GB34） on expression of hippocampal acetylcholinesterase, vesicular acetylcholine transporter, and muscarinic M1 receptor mRNA in chronic constrictive injury （neuropathic pain） and/or ovariotomy rats. Results demonstrated increased expression of hippocampal acetylcholinesterase, vesicular acetylcholine transporter, and muscarinic M1 receptor mRNA, as well as decreased pain threshold, in a rat model of chronic neuropathic pain after electroacupuncture. The effects of electroacupuncture increased with prolonged time, but the above-mentioned effects decreased in memory-deficient animals. Results indicated that repeated electroacupuncture has a cumulative analgesic effect, which is closely associated with upregulation of acetylcholinesterase and vesicular acetylcholine transporter activity, as well as M1 receptor mRNA expression and memory.

Cumulative second-harmonic generation of Lamb waves propagating in a two-layered solid plate

The physical process of cumulative second-harmonic generation of Lamb waves propagating in a two-layered solid plate is presented by using the second-order perturbation and the technique of nonlinear reflection of acoustic waves at an interface. In general, the cumulative second-harmonic generation of a dispersive guided wave propagation does not occur. However, the present paper shows that the second-harmonic of Lamb wave propagation arising from the nonlinear interaction of the partial bulk acoustic waves and the restriction of the three boundaries of the solid plates does have a cumulative growth effect if some conditions are satisfied. Through boundary condition and initial condition of excitation, the analytical expression of cumulative second-harmonic of Lamb waves propagation is determined. Numerical results show the cumulative effect of Lamb waves on second-harmonic field patterns.

Ecological risk assessment and early warning of heavy metal cumulation in the soils near the Luanchuan molybdenum polymetallic mine concentration area,Henan Province,central China

The Luanchuan molybdenum polymetallic mine concentration area is rich in mineral resources and has a long history of mining.The environmental impact of long-term mining activities cannot be ignored.It is of great significance to study the ecological risk and the accumulation trends of heavy metals in the soil of mining areas for scientific prevention and control of heavy metal pollution.Taking the Taowanbeigou River Basin in the mine concentration area as the research object,the ecological pollution risk and cumulative effect of heavy metals in the soil of the basin were studied by using the comprehensive pollution index method,potential ecological risk assessment method and geoaccumulation index method.On this basis,the cumulative exceeding years of specific heavy metals were predicted by using the early warning model.The comprehensive potential ecological risk of heavy metals in the soil near the Luanchuan mine concentration area is moderate,and the single element Cd is the main ecological risk factor,with a contribution rate of 53.6%.The overall cumulative degrees of Cu and Pb in the soil are“none-moderate”,Zn and Cd are moderate,Mo has reached an extremely strong cumulative level,Hg,As and Cr risks are not obvious,and the overall cumulative risks order is Mo>Cd>Zn>Cu>Pb>Hg.According to the current accumulation rate and taking the risk screening values for soil contamination of agricultural land as the reference standard,the locations over standard rates of Cu,Zn and Cd will exceed 78%in 90years,and the over standard rate of Pb will reach approximately 57%in 200 years.The cumulative exceeding standard periods of As,Cr and Hg are generally long,which basically indicates that these elements do not pose a significant potential threat to the ecological environment.Mining activities will accelerate the accumulation of heavy metals in soil.With the continuous development of mining activities,the potential pollution risk of heavy metals in the soil of mining areas will also increase.

Pulse repetition rate effect on the plasma inside femtosecond laser filament in air

The characteristics of plasmas play an important role in femtosecond laser filament-based applications.Spectroscopic analysis is used to experimentally investigate the plasma density and its temperature of the air filament under different pulse repetition rates.In our experiments,the measured average plasma density of the filament is 1.54×10^(17)cm^(-3)and the temperature of the plasma is about 5100 K under 100 Hz pulse repetition rate.The plasma density decreases to1.43×10^(17)cm^(-3)and the temperature increases to 6230 K as the pulse repetition rate increases to 1000 Hz.The experimental observation agrees with the numerical simulation by solving the nonlinear Schr?dinger equations with repetition rate related“low density hole”correction.

Analysis on Interrelation between Electroacupuncture-lnduced Cumulative Analgesic Effect and Hypothalamic Cholinergic Activities in Chronic Neuropathic Pain Rats

Objective： To observe the effects of repeated electroacupuncture （EA） of Zusanli （ST36）Yanglingquan （GB34） on hypothalamic acetylcholinesterase （AchE） and vesicular acetylcholine （ACh） transporter （VAChT） activities and choline acetyltransferase （CHAT） mRNA and muscarinic M1 receptor （MIR） mRNA expression in chronic constrictive injury （CCI） and/or ovariectomy （OVX） rats so as to reveal its underlying mechanism in cumulative analgesia. Methods： A total of 103 female Wistar rats were randomly divided into normal control （n=15）, CCI （n=15）, CCI＋EA2d （n=15）, CCI＋EA2W （n=15）, OVX＋CCI （n=13）, OVX＋CCI＋EA2d （n=15）, and OVX＋CCI＋EA2W groups （n=15）. CCI model was established by ligature of the unilateral sciatic nerve with surgical suture. Memory impairment model was established by removal of the bilateral ovaries. Morris water test was conducted to evaluate the OVX rats＇ memorylearning ability, and the thermal pain threshold （PT） of the bilateral paws was detected the next morning after EA. EA （2/15 Hz, 1 mA） was applied to bilateral ST36-GB34 for 30 min, once daily for 2 days or 2 weeks, respectively. Hypothalamic AChE activity was detected by histochemistry, VAChT immunoactivity was determined by immunohistochemistry, and ChAT mRNA and MIR mRNA expressions were assayed by reverse transcription-polymerase chain reaction （RT-PCR）. Results： In comparison with the normal control group, the AChE activity in hypothalamic arcuate nucleus （ARC） and supraoptic nucleus （SON） regions of CCI group, AChE activity in paraventricular nucleus （PVN）, ARC, and SON regions of OVX＋CCI group, and hypothalamic muscarinic M1R mRNA expression levels in both CCI and OVX＋CCI groups were down-regulated significantly （P〈0.05）. Compared with the CCI group, the AChE activities in hypothalamic ARC and SON regions of CCI＋EA2d and CCI＋EA2W groups and PVN region of CCI＋EA2W group and hypothalamic ChAT mRNA and M1R mRNA expression levels in CCi＋EA2W group were up-regulated considerably （P〈0.05）. In comparison with the OVX＋CCI group, the AChE activities in PVN, ARC, and SON regions and the expressions of hypothalamic ChAT mRNA and VAChT in ARC region of OVX＋CCI＋EA2W group were up-regulated remarkably （P〈0.05）. The effects in rats of CCI＋EA2W group were evidently superior to those of OVX＋CCI＋EA2d group in up-regulating AChE activities in PVN, ARC, and SON regions, VAChT immunoactivity in ARC region, and expression levels of hypothalamic ChAT mRNA and MIR mRNA （P〈0.05）. Similar situations were found in OVX＋CCI rats after EA2W. It suggested a cumulative effect after repeated EA of ST36-GB34. Comparison between CCI＋EA2W and OVX＋CCI＋EA2W groups showed that the effects in rats of the former group were evidently better than those of the latter group in up-regulating AChE activity in ARC and SON regions and the expressions of hypothalamic ChAT mRNA and M1 mRNA （P〈0.05）, suggesting a reduction of EA2W effects after OVX. Conclusion： Repeated EA can significantlyup-regulate AChE and VAChT activities and ChAT mRNA and MIR mRNA expressions in the hypothalamus of CCI and OVX＋CCI rats, which may contribute to the cumulative analgesic effects of repeated EA and be closely related to the animals＇ neuromemory ability.

Pulse repetition-rate effect on the intensity inside a femtosecond laser filament in air

As intense,ultrashort,kHz-repetition-rate laser systems become commercially available,pulse cumulative effects are critical for laser filament-based applications.In this work,the pulse repetition-rate effect on femtosecond laser filamentation in air was investigated both numerically and experimentally.The pulse repetition-rate effect has negligible influence at the leading edge of the filament.Clear intensity enhancement from a high-repetition pulse is observed at the peak and tailing edge of the laser filament.As the repetition rate of the laser pulses increases from 100 to 1000 Hz,the length of the filament extends and the intensity inside the filament increases.A physical picture based on the pulse repetition-rate dependent‘low-density hole’effect on filamentation is proposed to explain the obtained results well.

Replication of Prostate Cancer Risk Variants in a Danish Case-Control Association Study

Background: Prostate cancer is one of the main causes for cancer morbidity and mortality in Western countries. Recently, several single nucleotide polymorphisms (SNPs) associated with prostate cancer have been identified in genome-wide association studies and multiple variant models have been developed to predict prostate cancer risk. The association between genetic markers and clinico-pathological tumor variables has, however, been inconsistent. Methods and Materials: A total of 32 previously identified prostate cancer-associated risk SNPs were genotyped in 648 prostate cancer cases and 526 age-matched controls. Family history was obtained by questionnaire. Age at diagnosis, clinical tumor variables including pre- and postoperative PSA, Gleason score, and T stage were obtained from prospectively collected clinical data (Aarhus Prostate Cancer Study). The SNPs were genotyped using Sequenom and Taqman assays and associations between SNPs, prostate cancer risk, and clinico-pathological variables were assessed. Results: Seventeen SNPs were successfully replicated in our case-control study and the association estimates were consistent with previous reports. Four markers were excluded from further analysis due to linkage disequilibrium. The cumulative effect of having the disease-associated genotype at five SNPs (rs4430796, rs6983267, rs1859962, rs1447295 and rs16901979) increased the prostate cancer risk with odds ratio 6.02 (95% CI: 2.21 - 16.38;P = 1.0 × 10–4) in patients with any combination of ≥4 markers compared with patients without any of the five SNPs (P for trend = 1.0 × 10–4). Six markers were significantly associated with clinico-pathological variables: SNP rs2735839 (GG) at locus 19q13, which is in the KLK3 gene encoding PSA, was associated with high preoperative PSA (P = 0.04), low Gleason score (P = 0.01) and low T stage (P = 0.02). Variants rs5759167 (GG/GT) (22q13) and rs7679673 (CC/CA) (4q24) were correlated with low risk for biochemical relapse (P = 0.015 and P = 0.009, respectively), whereas rs6983267 (GG) (8q24) was significantly associated with biochemical recurrence (P = 0.045). In addition, variants rs6983267 (GG) and rs5759167 (GG/GT) were significantly associated with negative family history (P = 0.04 and P = 0.02, respectively). Conclusion: We replicated 17 previously identified prostate cancer-associated risk SNPs in a Danish case-control study and found a cumulative and significant association between five SNPs and prostate cancer. Overall, we noted significant associations between several prostate cancer-associated risk genotypes and less aggressive tumor variables, high level of PSA, and low risk for biochemical reccurrence.

Review on second-harmonic generation of ultrasonic guided waves in solid media(Ⅰ): Theoretical analyses

Considering the high sensitivity of the nonlinear ultrasonic measurement technique and great advantages of the guided wave testing method, the use of nonlinear ultrasonic guided waves provides a promising means for evaluating and characterizing the hidden and/or inaccessible damage/degradation in solid media. Increasing attention on the development of the testing method based on nonlinear ultrasonic guided waves is largely attributed to the theoretical advances of nonlinear guided waves propagation in solid media. One of the typical acoustic nonlinear responses is the generation of second harmonics that can be used to effectively evaluate damage/degradation in materials/structures. In this paper, the theoretical progress of second-harmonic generation（SHG） of ultrasonic guided wave propagation in solid media is reviewed. The advances and developments of theoretical investigations on the effect of SHG of ultrasonic guided wave propagation in different structures are addressed. Some obscure understandings and the ideas in dispute are also discussed.

Effects of Repeated Electroacupuncture on β-Endorphin and Adrencorticotropic Hormone Levels in the Hypothalamus and Pituitary in Rats with Chronic Pain and Ovariectomy

Objective： To explore the mechanism of electroacupuncture （EA）-induced cumulative analgesic effects on chronic pain in rats with or without ovariectomy （OVX）. Methods： A total of 110 female Wistar rats were randomized into normal control （n=10）, chronic constrictive injury （CCI, n=10）, CCI＋EA （n=30）, OVX＋CCI （n=30）, and OVX＋CCI＋EA （n=30） groups. Each of the latter 3 groups was further divided into 2 days （2 d）, 2 weeks （2 W） and 3 weeks （3 W） subgroups, respectively （n=10 in each subgroup）. The CCI pain model was established by ligature of the right sciatic nerve, and the memory impairment model duplicated by OVX. The paw withdrawal latency （PWL, pain threshold） of the bilateral footplates was detected by radiant heat irradiation, and the bilateral difference in PWL （PWLD） was used to evaluate changes in the pain reaction. Morris water maze test was conducted for evaluating the rats＇ learning-memory ability. EA was applied to bilateral Zusanli （ST36） and Yanglingquan （GB34） for 2 d, 2 W and 3 W, respectively. Pituitary and hypothalamic 13-endorphin （EP） and adrenocorticotrophic hormone （ACTH） contents were detected by immunoradioassay. Results： Compared with the CCI group, PWLD of the CCI＋EA-3 W group decreased significantly （P〈0.05）. Compared with the OVX＋CCI group, PWLD of the OVX＋CCI＋EA-3 W group was lowered considerably （P〈0.05）, but the value was markedly higher than its basal value and those of the normal control and CCI＋EA groups （P〈0.05）. In comparison with the sham-OVX group, the escape latency, swimming distance （SD） in the target quadrant and total SD were increased remarkably in the OVX group （P〈0.05）, while the number of target platform crossings was decreased significantly （P〈0.05）, suggesting an impairment of the OVX rats＇ learning-memory ability. In simple CCI rats, both β-EP and ACTH contents of the pituitary increased markedly （P〈0.05）, and those of the hypothalamus decreased obviously compared to the normal control group （P〈0.05）. After EA, pituitary and hypothalamic ACTH levels were significantly lowered at 2 d and hypothalamic ACTH and β -EP contents increased obviously at 3 W in comparison with the CCI group （P〈0.05）. In OVX＋CCI rats, following EA, pituitary β -EP contents at 2 d, 2 W and 3 W, and hypothalamic β-EP and ACTH contents at 2 W and hypothalamic ACTH levels at 3 W increased significantly （P〈O.05）, but hypothalamic β-EP level at 3W decreased markedly （P〈0.05）. The effects of repeated EA in lowering pituitary ACTH and raising hypothalamic β-EP and ACTH levels disappeared after OVX＋CCI. Conclusions： Repeated EA has a cumulative analgesic effect, which is closely associated with its effects in regulating pituitary and hypothalamic β-EP and ACTH levels. OVX may weaken the analgesic effect of EA by affecting hypothalamic-pituitary axis activity.