Influence of density on the post-suffusion behavior of gap-graded sand with fines

Suffusion erosion, characterized as the selective detachment and transportation of finer particles by seepage flow, is hazardous to the stability and serviceability of geotechnical structures. The removal of finer particles deteriorates the structure and fabric of the soil, leading to the degradation of its mechanical properties. Studies into the effects of suffusion on mechanical behavior have so far produced disparate results depending on the pre-erosion relative density of the specimens tested. To investigate this issue, small cyclic and monotonic loading tests were performed on intact and eroded gap-graded silty sand specimens in three dispersed density states, using a triaxial cell modified for the purpose of erosion. The variation of Young's modulus showed an inverse relationship with the pre-erosion density of the specimen, as the small strain stiffness decreased in the dense cases and increased in the loose cases. Conversely, Poisson's ratio increased in value as suffusion progressed regardless of the initial density of the specimens. In the contractive phase of monotonic loading, the densification of the coarse soil skeleton by the downward seepage flow resulted in a decrease in contractiveness and an increase in secant stiffness. In the dilative phase, the increase in porosity by the erosion of finer particles reduced the dilatancy and peak strength of the specimens. The results suggest that the pre-suffusion density determines the primary locus of affected mechanical behavior in triaxial compression, which shifts from the contractive phase to the dilative phase with the increase in pre-suffusion density. The critical state strength, inferred using stress–dilatancy theory, was largely unaffected by the erosion of finer particles. As the results indicate, pre-erosion density may be of practical significance in assessing the vulnerability to deterioration and collapse of geotechnical formations and structures subjected to suffusion erosion.     

一种新的密码本原:棘轮密钥交换的定义、模型及构造

在传统密码学应用中,人们总假定终端是安全的,并且敌手只存在于通信信道上。然而,主流的恶意软件和系统漏洞给终端安全带来了严重和直接的威胁和挑战,例如容易遭受存储内容被病毒破坏、随机数发生器被腐化等各种攻击。更糟糕的是,协议会话通常有较长的生存期,因此需要在较长的时间内存储与会话相关的秘密信息。在这种情况下,有必要设计高强度的安全协议,以对抗可以暴露存储内容和中间计算结果(包括随机数)的敌手。棘轮密钥交换是解决这一问题的一个基本工具。文中综述了密码本原——棘轮密钥交换,包括单向、半双向和双向等棘轮密钥交换的定义、模型及构造,并展望了棘轮密钥交换的未来发展趋势。     

E7766, a Macrocycle-Bridged Stimulator of Interferon Genes (STING) Agonist with Potent Pan-Genotypic Activity

A strategy for creating potent and pan-genotypic stimulator of interferon genes (STING) agonists is described. Locking a bioactive U-shaped conformation of cyclic dinucleotides by introducing a transannular macrocyclic bridge between the nucleic acid bases leads to a topologically novel macrocycle-bridged STING agonist (MBSA). In addition to substantially enhanced potency, the newly designed MBSAs, exemplified by clinical candidate E7766 , exhibit broad pan-genotypic activity in all major human STING variants. E7766 is shown to have potent antitumor activity with long lasting immune memory response in a mouse liver metastatic tumor model. Two complementary stereoselective synthetic routes to E7766 are also described.     

Stem Photosynthesis—A Key Element of Grass Pea (Lathyrus sativus L.) Acclimatisation to Salinity

Grass pea (Lathyrus sativus) is a leguminous plant of outstanding tolerance to abiotic stress. The aim of the presented study was to describe the mechanism of grass pea (Lathyrus sativus L.) photosynthetic apparatus acclimatisation strategies to salinity stress. The seedlings were cultivated in a hydroponic system in media containing various concentrations of NaCl (0, 50, and 100 mM), imitating none, moderate, and severe salinity, respectively, for three weeks. In order to characterise the function and structure of the photosynthetic apparatus, Chl a fluorescence, gas exchange measurements, proteome analysis, and Fourier-transform infrared spectroscopy (FT-IR) analysis were done inter alia. Significant differences in the response of the leaf and stem photosynthetic apparatus to severe salt stress were observed. Leaves became the place of harmful ion (Na⁺) accumulation, and the efficiency of their carboxylation decreased sharply. In turn, in stems, the reconstruction of the photosynthetic apparatus (antenna and photosystem complexes) activated alternative electron transport pathways, leading to effective ATP synthesis, which is required for the efficient translocation of Na⁺ to leaves. These changes enabled efficient stem carboxylation and made them the main source of assimilates. The observed changes indicate the high plasticity of grass pea photosynthetic apparatus, providing an effective mechanism of tolerance to salinity stress.     

普通食用油检验关键点分析

以实际案例和文献资料收集为基础,主要围绕食用油检测从采样到结果判定一系列过程中可能涉及的操作风险点进行分析,并对部分典型检验指标(苯并(a)芘、塑化剂、抗氧化剂、残留溶剂、过氧化值、酸价、辣椒素、黄曲霉毒素B1)进行分析,介绍了分析过程中实验室环境、接触器具、试剂、样本本底、特殊基质干扰、指标稳定性等对实验结果有关键影响的因素,并针对具体问题提出解决措施,旨在为食用油检验风险防控提供技术支撑。     

西部山地旅游公共服务游客满意度评价研究——以318国道川藏线为例

文章在对相关研究进行文献综述的基础上,以318国道川藏线为例,提出西部山地旅游公共服务5个维度的游客感知假设,选用偏最小二乘结构方程模型(PLS-SEM)对游客满意度组合模型进行因子分析与假设检验。根据模型拟合结果分析,旅游信息类公共服务在西部山地旅游公共服务中供需矛盾最为突出,其次为旅游交通类公共服务和旅游安全保障管理类公共服务,相对而言,旅游基础设施类公共服务和休闲空间与旅游便民惠民类公共服务供需矛盾较小。该结果为西部山地旅游公共服务体系构建明确了发展方向。     

Interrelated Mechanism by Which the Methide Quinone Celastrol,Obtained from the Roots of Tripterygium wilfordii,Inhibits Main Protease 3CLpro of COVID-19 and Acts as Superoxide Radical Scavenger

We describe the potential anti coronavirus disease 2019 (COVID-19) action of the methide quinone inhibitor, celastrol. The related methide quinone dexamethasone is, so far, among COVID-19 medications perhaps the most effective drug for patients with severe symptoms. We observe a parallel redox biology behavior between the antioxidant action of celastrol when scavenging the superoxide radical, and the adduct formation of celastrol with the main COVID-19 protease. The related molecular mechanism is envisioned using molecular mechanics and dynamics calculations. It proposes a covalent bond between the S(Cys145) amino acid thiolate and the celastrol A ring, assisted by proton transfers by His164 and His41 amino acids, and a π interaction from Met49 to the celastrol B ring. Specifically, celastrol possesses two moieties that are able to independently scavenge the superoxide radical: the carboxylic framework located at ring E, and the methide-quinone ring A. The latter captures the superoxide electron, releasing molecular oxygen, and is the feature of interest that correlates with the mechanism of COVID-19 inhibition. This unusual scavenging of the superoxide radical is described using density functional theory (DFT) methods, and is supported experimentally by cyclic voltammetry and X-ray diffraction.     

HACCP在浓香菜籽油生产中的应用

为了保障浓香菜籽油的产品质量安全,采用HACCP体系对浓香菜籽油生产全过程进行生物、物理、化学的危害分析,确定关键控制点,制定预防措施,并对生产环节进行有效监控,制定纠偏措施,做好记录管理,为浓香菜籽油的安全生产提供借鉴。     

Economic effects of regulating the seismic strengthening of older buildings

The marked increase in the awareness of earthquake risk following the Canterbury earthquakes in New Zealand offered a unique opportunity to investigate the economic effect of disaster-mitigation regulations on the commercial building stock. A difference-in-differences (DD) framework was used to determine whether earthquake risk has been capitalized into the property prices of buildings constructed prior to 1976, as a response to the national policy requiring assessment and strengthening (or demolition) of the existing earthquake-prone building stock. A negative externality is found in the policy announcement on affected (pre-1970s) office and retail buildings which caused office buildings to suffer a 12.5% stigma discount. However, retail properties were less impacted suffering a 2.3% stigma loss. The value of the commercial building stock has been affected by the policy. These findings provide policy-makers with timely evidence as to the economic effects of New Zealand’s earthquake-prone buildings policy. Facing losses in property value and financial responsibility for retrofitting their assets, building owners will be looking for a workable set of regulatory and non-regulatory incentives to encourage disaster risk management and protect the built environment.     

采动覆岩卸荷膨胀累积效应

地下煤层开采引起的岩层运动是一系列安全和环境问题的根源,研究采动岩层运动规律是安全、高效、绿色开采的重要基础。通过对岩层运动过程的研究,揭示了采动覆岩卸荷膨胀累积效应及其对岩层运动规律的影响机制。研究表明:采动覆岩经历了卸荷膨胀与再压实的动态过程。受关键层结构控制,上覆岩层由下向上成组破断运动,关键层破断前,阻断了上覆载荷向下方岩层的传递,导致其因卸荷而产生膨胀,包括碎胀与弹性膨胀。随着关键层破断高度增加,覆岩卸荷高度同步增大,因卸荷而膨胀的岩层总厚度不断增大;同时卸荷煤岩也受到已破断关键层载荷的压实作用,从而造成覆岩卸荷膨胀总量的不断变化。将这种覆岩卸荷膨胀总量随覆岩卸荷高度动态变化的现象定义为采动覆岩卸荷膨胀累积效应,进而建立了理论模型,并通过淮北海孜煤矿巨厚火成岩下采煤覆岩裂隙实测进行了验证。结果表明,采动覆岩卸荷膨胀累积效应对采动岩层运动规律产生了重要影响,如影响覆岩关键层下离层量,影响覆岩关键层贯通破断的高度,影响不同开采条件的地表下沉系数等。采动覆岩卸荷膨胀累积效应改变了对离层存在形式的传统认识,该效应的存在导致关键层下最大离层量一般小于采高的10%,覆岩可注浆充填空间并非传统认识上的“离层区”,而主要是注浆充填压力“压实”作用下将覆岩卸荷累积膨胀所转化出的那部分空间,该发现指导了覆岩隔离注浆充填绿色开采技术的创新研发及其在建筑物压煤开采中的成功实践。