Acute Toxicity and Anthelmintic Effects of Gomphrena serrata L. (Amaranthaceae) Extracts on Adult Worms and Eggs of Haemonchus contortus

Gomphrena serrata L. (Amaranthaceae) is a medicinal plant widely used traditionally in rural areas to treat many diseases, including gastrointestinal helminthiasis of small ruminants. This work aims to estimate the plant extracts phytochemical potential and study the activities of the aqueous decoction (GS_AD), aqueous macerate (GS_AM), and hydroalcoholic macerate (GS_HEM) of Gomphrena serrata extracts on two developmental stages (eggs and adult worms) of Haemonchus contortus. Phytochemical screening was carried out. The acute toxicity test was performed according to the Organisation for Economic Co-operation and Development (OECD) test guideline 423. The Haemonchus contortus eggs hatching inhibition test was performed left to incubate for 48 hours in the presence of the different plant extracts at increasing concentrations of 0.125;0.25;0.5;0.625;1;2;3 mg/mL. For the motility inhibition test on adult worms, the worms were contacted with the extracts at concentrations of 0.75;1;1.25;1.5;2;3;4 mg/mL and left to incubate for 24 hours. Albendazole and levamisole were used as standard. Phytochemical screening revealed the presence of tannins, saponins, reducing compounds, coumarins and derivatives, anthocyanins, steroids, triterpenes, and flavonoids. An acute toxicity study showed that the oral LD50 value of G. serrata was estimated to be 5000 mg/kg. All extracts showed an effect on both stages of parasite development. The hatching inhibition rate was 100% from 3 mg/mL for all three extracts. The rate of inhibition of motility was 100% from 4 mg/mL for each extract. HEM is more efficient on eggs and Haemonchus contortus adult worms than other extracts with IC50 of 0.457 mg/mL and LC50 of 1.329 mg/mL, respectively. These results suggest that Gomphrena serrata, a plant used by farmers, has anthelmintic properties.

Anti-Inflammatory and Antioxidant Properties of the Aqueous Extracts of the Leaves of Opilia amentacea (Opiliaceae)

Opilia amentacea (Opiliaceae) is a woody plant with multiple medicinal claimed effects. The present study aimed to assess the anti-inflammatory and antioxidant activities of the decoction and macerate extracts from the leaves of Opilia amentacea. Moreover, acute toxicity and phytochemical analysis were performed. The acute toxicity was evaluated on NMRI mice at 2000 mg/kg bw. The anti-inflammatory activity was studied using the carrageenan-induced mouse paw edema and the lipoxygenase inhibition assay. The radical scavenging (DPPH and ABTS), ferric-reducing antioxidant power (FRAP), and lipid peroxidation (LPO) assays were used to measure the antioxidant capacity of the extracts. Qualitative and quantitative methods served for identifying and quantifying the extract’s phytoconstituents. The decoction demonstrated low acute toxicity;the lethal dose was therefore estimated to be superior to 2000 mg/kg bw. The extracts significantly reduced the mouse paw’s thickness at 600 mg/kg bw. The extracts developed weak radical scavenging and lipid peroxidation inhibitory effects. However, the macerate showed a high ability (664.90 ± 0.71 mol Ascorbic Acid Equivalent/g dry extract) to reduce the ferric ions. Saponins, sterols, triterpenes, and flavonoids were qualitatively detected in the two extracts. Total phenolics (TP) and total flavonoids (TF) were found abundant in the extracts, especially the decoction (TP content (TPC) = 94.03 ± 2.66 mg GAE/g;TF content (TFC) = 35.05 ± 0.32 mg QE/g). Strong positive correlations existed between ferric-reducing capacity and TPC (r = 0.959) for the macerate, while TFC was mainly involved in the DPPH radical scavenging of the two extracts. Instead, most correlations were negative between the polyphenol compounds and the anti-inflammatory assays. The results indicate potent in vivo anti-inflammatory and in vitro antioxidant effects of the aqueous extracts from the leaves of Opilia amentacea. Further studies are needed to find the anti-inflammatory and antioxidant effects mechanism.

Acute Oral Toxicity and Vasorelaxant Effects of Hydroethanolic Extract from Lannea microcarpa Engl. & K. Krause (Anacardiaceae) Trunk Barks in Mice Aortas: Possible Involvement of Intracellular Ca 2+ Mobilization

Lannea microcrapa Engl. & K. Krause (Anacardiaceae) is a fruit and medicinal plant widely used in Burkina Faso. This plant is traditionally used in the treatment of hypertension. The aim of the present study was to evaluate the vasorelaxant effects of the hydroethanolic extract from Lannea microcarpa trunk barks (HE_ELM) on the aorta isolated from NMRI mice. Phytochemical screening by HPTLC, assay of phenolic and flavonoid compounds, assessment of antioxidant activity (DPPH, ABTS, FRAP, and LPO), and myography of HE_ELM (1 - 2000 μg/mL) on mice thoracic aortas in the presence and absence of endothelium were carried out. Endothelium-dependent and endothelium-independant vasodilation were assessed by cumulative addition of Ach (1 nM - 10 μM) on aortic rings precontracted with the thromboxane analogue A2 agonist, 9,11-dideoxy9α,11α-methanoepoxy PGF2α (U46619). L-NAME was used to verify the involvement of NO production in the relaxation mechanism of the extract. Acute oral toxicity of HE_ELM was also evaluated. A phytochemical study revealed the presence of tannins, flavonoids, sterols and triterpenes, saponosides, and high levels of total phenolics and flavonoids. These compounds are thought to be responsible for the extract’s antioxidant and vasorelaxant properties. HE_ELM demonstrated significant antioxidant potential and induced aortic relaxation. Indeed, pharmacological parameters gave EC50 values ranging from 596.45 ± 95.82 μg/mL to 749.48 ± 133.40 μg/mL and Emax values from 85.51% ± 9.59% to 96.81% ± 8.60% for the three conditions of vasodilation of the extract (p > 0.05). A complete antagonism of the contractile effect of U46619 was noted with 1 mg/mL HE_ELM. These results suggest that HE_ELM induces aortic relaxation through a concentration-dependent, endothelium-independent mechanism, possibly involving intracellular calcium mobilization of vascular cells. Acute oral toxicity tests of HE_ELM (2000 mg/kg) showed no mortality or adverse effects, suggesting the extract’s safety and potential as a therapeutic agent for hypertension. This discovery scientifically validates the use of the plant in alternative medicine to treat hypertension.

Phytochemical Analysis and Contractile Effects of Aqueous and Hydroethanolic Extracts of Anastatica hierochuntica L. (Brassicaceae) on the Isolated Uterus of Mice

Background: Anastatica hierochuntica L. (Brassicaceae) has been claimed to treat various conditions, including complicated childbirth. The principal objective of this research was to provide scientific evidence on the contractile effect of the aqueous and hydroethanolic extracts of the whole plant from A. hierochuntica during labor. Method: Qualitative and quantitative methods helped identify and quantify the phytoconstituents in both extracts. The antioxidant activity was studied using four standard methods (ABTS, DPPH, FRAP, and LPO). Results: The inhibitory power of the extracts on pro-inflammatory enzymes such as 15-lipoxygenase and phospholipase A2 was determined. The contractile effects of the extracts were evaluated using isolated pregnant mice uteri. Steroids, triterpenoids, flavonoids, tannins, coumarins, and reduced compounds were identified in both extracts. The hydroethanolic extract exhibited higher content of hydrolyzable tannins (15.07 ± 0.24 mg tannic acid equivalent/g) than the aqueous decoction (11.8 ± 0.69 mg TAE/g). The extracts demonstrated the ability to scavenge DPPH and ABTS radicals, reduce ferric ions, and inhibit especially lipid peroxidation. No significant difference was noted in the phospholipase inhibition between the extracts and betamethasone. The hydroethanolic extract displayed the most significant anti-lipoxygenase activity with an IC50 value of 55.82 ± 1.15 μg/mL. The lethal dose (LD50) of extracts was estimated to be superior to 2000 mg/kg body weight (bw). The ability of the samples to produce one cm amplitude of contraction at 50% effective concentrations (EC50) was 5.33 × 10−8 ± 0.32 mg/mL for oxytocin, 1.51 ± 0.08 mg/mL for aqueous extract and 3.57 ± 0.61 mg/mL for hydroethanolic extract. Conclusion: These findings could provide evidence for using Anastatica hierochuntica to facilitate childbirth.

CHARACTERISTICS OF MUCINS AND CEA IN GLOBOID DYSPLASTIC CELLS OF HUMAN STOMACH AND ITS RELATIONSHIP WITH SIGNET RING CELL CARCINOMA

Fourty-three cases of globoid dysplasia and signet ring cell carcinoma were stained by mucin and CEA (ABC method). It was found that there were three kinds of mucins (neutral, sialo and sulphomucin in both globoid dysplastic cells and signet ring cells. The percentages of the three kinds of mucins seen in the two kinds of cells were not much different. It was indicated that the altered mucins in the gastric epithelial cells must be a sign of dedifferentiation of the cells and the results of malfunction. The globoid dysplasia type I mainly contained neutral mucin, whereas type II, the acid mucin was predominant, especially the sulphomucin. The CEA positive reaction became stronger as the atypia being remarkable, and the characteristics of distribution of CEA positive particles were similar in the two kinds of cells namely, randomly or disorderly in the cells. Based on the analysis of the results, a conclusion can be made that the variety of mucins in globoid dysplastic cells can be used as a reference point in classification and is not much significant in grading, but the amount of CEA positive matter can be a reference point in grading. The globoid dysplasia is such a lesion with special features in morphology and function manifested in the process of de-differentiation towards signet ring cell carcinoma following the successive action of carcinogens upon the cells of gastric epithelium.

Pseudomonas brassicacearum的数量分布差异及生物防治小麦全蚀病和油菜根腐病(英文)

通过3种PCR技术测定基因特征和测定3种生化特征,对来自南澳洲两块对比小麦田土壤中的Pseudomonasbrassicacearum种群的菌株进行了分析研究。结果显示,两种不同土壤和两种不同根部区域(根表和根际),该种群具有高度多样性,其基因型和基因组也具有显著差异(P<0.05)。所分离到的菌株中,四分之三具有独特的基因组,90%以上的基因组是其原种群所独具有的。所有菌株的基因组的平均同源性比较低(22%),聚类分析不能证明来自不同小麦田和不同根部区域的菌株具有亲缘性。聚类分析显示,种群内的基因流动是受到限制的,菌株基因组的差异是由于基因的随机漂流引起的,由根表得到的基因型是与所采集的对比土壤相关联的。有三分之一的菌株检测到了2,4二乙酰基均苯三酚(PhlD)生物合成基因,这些菌株形成了一相关联的组群(同源性为60%)。4株产生PhlD的菌株(两种野生型,表型不同)对小麦全蚀病和腐霉引起的油菜根腐病具有显著的防治效果,展现出了对这类病原菌引起的根部病害的防治潜能。

DISTRIBUTION AND ULTRASTRUCTURAL LOCALIZATION OF CARCINOEMBRYONIC ANTIGEN (CEA) IN SIGNET RING CELLS OF GASTRIC CANCER

The distribution and ultrastructural localization of CEA in signet-ring cells of 15 gastric cancer specimens were observed by PAP and immunoelectron microscopic methods. The mechanism of abnormal distribution of CEA in the signet-ring cell and its biological significance are discussed. The results showed that the CEA positive rate in signet-ring cells was 100% with the polarity lost in distribution. Under the light microscope, the CEA stain patterns were of two types: cytoplasmic and membranous types. The former was predominant. Under the electron microscope, most of the CEA was distributed on the cell membrane and cytoplasm. CEA was found in intracellular membranous structure of the cancer cells, especially in protein synthesis and transport organellae (RER, Golgi Complex etc.). The synthesis of CEA in cancer cells increased, yet its elimination was somewhat hampered. The result was that the RER became extended and were full of CEA (+) material. In the free signet-ring cell, there was a small and short contact plane. The tight junction was severed as the cell junction reduced. The antigenic determinant of CEA was glycoprotein. The abnormal distribution of CEA in signet-ring cells might be the morphologic reflection of the glycosylation of surface glycoprotein of tumor cells.

土工格栅加筋粉煤灰改良黄土力学特性研究

随着西部黄土地区城镇化进程的加快,填挖结合的新增用地方式要求地基处理技术需要重点解决填方区的强度与变形问题。论文将粉煤灰作为改性填料对黄土进行改良,通过直剪试验、三轴试验、湿陷试验与扫描电镜试验,分析不同粉煤灰掺入比条件下加筋与未加筋黄土试样的强度变化规律、宏观破坏特征和微结构特征。结果表明:采用粉煤灰改良和土工格栅加筋后,黄土的最优含水率增大,最大干密度降低。当粉煤灰掺入比λ=20%时,加筋改良效果最好,黄土的峰值强度、残余强度和等效内摩擦角均有大幅提高,侧向变形显著减小,且能有效降低其湿陷性。微结构分析表明:粉煤灰对黄土的改良主要体现在颗粒直接填充和化学结晶体交织成的网状填充两种类型的强化作用,改良后黄土的孔隙率与孔隙尺寸均有所下降。研究结果可为黄土地区填方边坡与填方路基的改良加固提供参考。

我国黄土高原地区地震动衰减关系研究的若干进展

地震动的衰减关系是指地震动随震级、距离和场地条件等变化的经验关系,近年来在我国亦被称为地震动预测方程,是估计地震动及其影响场的主要方法之一,在地震区划和重大工程场地地震安全性评价中被广泛应用。黄土是一种特殊土,在我国广泛分布。我国黄土高原地区地质构造复杂,新构造活动强烈,中强地震频发,地震动的衰减关系有其特殊性,总结我国黄土高原地区地震动衰减关系的研究成果对促进黄土高原地区抗震研究有重要意义。在简要介绍国内外地震动衰减关系研究的基础上,全面系统地总结我国学者在黄土高原地区的地震烈度衰减关系,基岩和土层场地地震动峰值加速度、峰值速度、峰值位移以及反应谱衰减关系方面的研究成果;评述和讨论在黄土覆盖地区地震动衰减研究领域存在的问题和今后的研究方向。文章的研究工作对从事黄土高原地区地震工程研究的科技人员有重要参考价值。

新疆乌什7.1级地震前GNSS变形特征分析

2024年1月23日新疆乌什发生7.1级地震。为了研究震前GNSS变形特征,通过对比分析GNSS基线时间序列结果和区域应变结果,发现迈丹断裂带东西两段的地壳运动有所差异,东段的运动较强,乌什地震即发生在断裂带东段;利用4期速度场结果,计算得到动态应变场变化,从NS向应变场结果可以看出该区域的应变量值持续增加,应变持续在积累状态,从长期背景场可以看出7.1级地震发生在应变高值区的边缘;发震断层东西两侧的挤压滑动速率存在明显差异,西侧为(1.0±0.35)mm/a,东侧为(4.1±0.51)mm/a,且东侧的闭锁程度较高。研究认为迈丹断裂带两侧运动差异明显,乌什7.1级地震发生在滑动速率较高的东段,且该区域处于应变高值区的边缘。

湖北襄阳地区土体剪切波波速与深度的相关性研究

为给出湖北襄阳地区典型粘性土、粉土、砂土及碎石土剪切波波速与深度之间的统计公式,基于收集到的102个实测钻孔波速资料,利用多种一元回归模型对襄阳地区常见土层剪切波波速与深度之间的关系进行拟合分析和相关性研究;同时,讨论土体状态对二者关系的影响;最后,利用实测钻孔数据验证统计公式的合理性和可靠性。研究结果表明:1)除人工填土外,襄阳地区其他常规土类剪切波波速与深度之间存在较强的相关性,且离散程度随深度的增加而增大;2)同一土类随密实度或塑性状态的增大,其平均剪切波波速也变大;3)考虑土体状态可以使回归模型的预测结果更加具体、更接近真实值,但对模型拟合优度的变化具有不确定性;4)区域性对土层剪切波波速与深度的统计关系有较大影响。本文研究的襄阳地区各土类剪切波波速回归模型较全国土类模型具有更好的预测精度和误差平稳性,可为南襄盆地及周边区域地震灾害风险普查、场地土动力学性质研究和地震动参数确定等提供参考。

泸定M S6.8地震震前变形特征及鲜水河断裂南东段地震活动性

针对鲜水河断裂带南东段的历史地震活动性和近10 a该断裂带上发生的中小震群展布特征,利用GNSS观测数据给出2022年泸定M S6.8地震震源区及周边区域的速度场、应变率场,识别此次地震震前的变形特征。GNSS速度场显示,鲜水河断裂带南东段走滑速率约为10 mm/a,区域整体运动为ES向,与断裂构造运动具有一致性;应变率场结果显示,发震断裂仍存在较强的剪切应变积累,汶川特大地震后随着应变能不断释放,龙门山断裂带的卸载作用间接影响鲜水河断裂带的南东段,该断裂长期处于应变积累高值的过渡区,现今仍具有较高的断层闭锁状态,该地区的地震活动趋势和地震危险性值得进一步关注和研究。

湖北省域不同超越概率水平下地震动峰值加速度比例关系

以第一次全国地震灾害风险普查工作成果为依据,计算并分析湖北省域不同超越概率水平下峰值加速度之间的比例关系及其空间分布特征。利用湖北省域宏观场地类别数据,计算得到湖北省域在多遇地震、基本地震和设防地震作用下场地峰值加速度比例关系:在0.05 g加速度分区中,湖北省域场地50 a超越概率63%与10%的峰值加速度比例(R_(63)/R_(10))均值为0.31,超越概率2%与10%的峰值加速度比例(R_(2)/R_(10))均值为1.81;在0.10 g加速度分区中,R_(63)/R_(10)均值为0.30,R_(2)/R_(10)均值为1.80;在0.15 g加速度分区中,R_(63)/R_(10)均值为0.17,R_(2)/R_(10)均值为1.98。在此基础上,与现行《建筑抗震设计规范》、《中国地震动参数区划图》等强制性国家标准中要求的比例进行对比分析,认为湖北省域采用《建筑抗震设计规范》中的取值对建筑物进行抗震作用计算,所考虑的地震作用是保守且安全的。同时,在湖北省高烈度区(如竹山、竹溪)开展地震危险性分析和地震灾害风险防治工作时,多遇地震下的地震动峰值加速度值宜按不低于基本地震动峰值加速度的1/3进行调整。该研究成果将有助于湖北省地震风险普查成果的推广和应用。

基于环境激励的厦门财富中心动力参数实测分析

为揭示环境激励下不同测点反映的模态信息情况,在厦门财富中心布置结构台阵获取环境激励下的结构振动响应。采用Welch平均周期图法获得功率谱密度(power spectral density,PSD)曲线,并在此基础上识别结构模态参数。比较不同测点的PSD曲线和模态识别结果,并与有限元结果进行对比。结果表明:1)结构基底、自由场地和基岩场地三个测点PSD曲线在0.1~1.0 Hz频段高度相似,该频段是由场地次级微地震引起的;不同之处在于结构基底测点PSD曲线Z向峰值是结构竖向基频,而自由场地峰值是场地基本频率。2)结构低楼层测点主要反映其测试方向上的模态频率,而高楼层测点能够反映多方向的模态频率。高楼层测点反映的模态信息更丰富,但易受到密集模态的影响。3)有限元结果与实测结果接近,表明有限元模型可以较好地反映结构的真实动力特性。

地震亚失稳过程中前兆异常演化的综合解释——以2014年鲁甸6.5级地震为例

文中以2014年鲁甸6.5级地震为例,在亚失稳实验及理论指导下,基于震前地震活动及地球物理观测资料并结合地震成核数值模拟结果,综合分析前兆异常时空演化与亚失稳过程的关系,首次提供了一个可明确佐证亚失稳阶段震源区成核、震源区附近协同化过程持续加剧的典型震例和观测事实。研究结果显示,依据大区域强震活动及流动重力观测,可判定鲁甸地震前研究区已处于高应力状态。在高应力背景判定的基础上,依据地震活动及地球物理观测前兆异常,可粗略判定鲁甸地震亚失稳过程可能起始于震前7、8个月,最突出的现象或判定指标是由震中附近小地震活跃所表征的断层应力状态由积累为主向释放为主的转变,以及由定点地球物理观测异常数量显著增加所表征的断层运动协同化现象,从地震成核的角度与成核后期核心弱化区扩张过程有关。之后至主震发生,还有2个时间节点需要关注:一是震前4、5个月,定点地球物理观测异常空间分布范围自震中附近向外围的明显扩展,显示断层变形的加速协同化;二是震前2个月之后,震中附近小地震活动开始减弱、微震活动及定点地球物理异常出现向震中的迁移收缩,与地震成核过程核心弱化区扩展之后的收缩过程相关联。

2023年12月18日甘肃积石山M 6.2地震的前兆异常和孕震过程

为了寻找确切的地震前兆异常,在2023年12月18日甘肃积石山M 6.2地震后,对甘肃省临夏地震台观测资料进行分析,发现临夏台所处地块从2023年1月10日起就处在构造应力的作用下,地块内裂隙张开,吸纳空气,导致钻孔与地面气压差ΔP负异常;从2月22日起,自然电位差ΔV和单极电阻率ρK相继出现异常变化;从3月16日起,开始了小幅度的预滑活动Xpo,并于8月11日前后达到峰值Xpm。预滑活动使临夏台所处地块内多个小裂隙快速张开,并吸纳气体,导致钻孔气压在12月6日起出现多个负气压脉冲G P,这些异常现象直到震后才结束。震前十几个小时的临震预滑活动使得积聚在孕震断层上的应力进一步加大,克服了断层面上的摩擦力,导致孕震断层失稳破裂,发生了积石山M 6.2地震。鉴于观测到的预滑活动和前兆异常发生的时间、空间都与积石山M 6.2地震有较好的相关性,推测临夏台震前观测到的地块预滑活动、气压差变化、气压脉冲、自然电位差和单极电阻率变化可能是M 6.2地震的前兆异常。前兆异常时空演化过程表明,积石山M 6.2地震的孕震过程分4个阶段。因此,关注震前地块预滑活动和各类前兆异常,对预测未来破坏性地震和研究孕震过程有一定的前兆意义。

用于数据采集器测试的时间脉冲插值分析方法

地震数据采集器时间服务精度是评价设备性能的重要指标,一般使用标准时间源输出的时间脉冲信号采样数据进行分析计算,但受仪器采样率限制,时间偏差测试分辨率不高。设计了基于一阶差分和直方图分析的脉冲信号上升沿识别、高低电位分析和时间偏差分析算法,研究使用非线性插值分析方法对地震数据采集器采集的标准时间脉冲信号进行波形升采样恢复,并基于所提算法进行实验分析和讨论,在提高地震数据采集器时间偏差测试分辨率的同时,规范了测试数据处理方法和流程。

土动力学与岩土地震工程

社会发展需求的增长、工程建造能力的提升以及气候变化等环境因素的改变带来的新震害现象、技术手段和工程需求,为土动力学及岩土地震工程研究提出了新挑战并创造了新机遇。文章重点针对近年来土动力学与岩土地震工程领域的一些新现象、新手段和新挑战进行综述,聚焦于土的动力特性、砂土地震液化、土的动力测试和岩土地震工程试验、岩土地震工程数值模拟以及岩土工程抗震等方面,分析当前理论研究和工程实践所面临的新问题和新挑战,梳理近年来所取得的一些最新进展,并对今后的研究方向进行探讨。

基于多层全连接神经网络的6C地震波极化向量识别研究

利用机器学习原理,提出一种基于多层全连接(multi-layer fully connected, MFC)神经网络的六分量(six-component, 6C)地震波极化向量识别方法。首先利用6C地震波各波型极化向量数学模型和一系列仿真参数得到5种波型和噪声波型各5 000个极化向量数据集,然后随机选取其中5 000个作为测试集,其余划分为训练集,进行MFC神经网络与支持向量机(support vector machine, SVM)的综合辨识性能对比实验。结果表明,MFC神经网络模型识别5种极化向量类型(SH波和Love波视为一类)和6种极化向量类型的效果均显著优于SVM模型,平均识别率分别达到99.786%和87.940%。

积石山M6.2地震诱发秦阴村黄土震陷灾害研究

2023年12月18日在甘肃省临夏州积石山县发生的M6.2地震诱发了多处黄土震陷灾害。通过对积石山县石塬镇秦阴村黄土震陷灾害进行现场调查,得出灾害的主要特征;利用原状黄土开展室内试验,研究秦阴村黄土的物性参数特征、微结构特征和震陷性,结合现场调查结果分析震陷灾害产生的主要原因。研究结果表明:秦阴村震陷区内土体酥裂,裂缝发育,边缘土体坍落或产生滑坡;土层呈反倾台阶状震裂破坏,最大沉降量57 cm,裂缝最大长度约300 m,宽度约83 cm。震陷区黄土土质疏松、含水率较高、架空孔隙发育、颗粒胶结较弱,具备产生震陷的土性条件。震陷区黄土层厚度较大,地震的等效动应力大于土体产生震陷的临界动应力,且地震动持续时间较长、卓越周期较大,使得场地产生了严重的震陷破坏。