电信运营市场上过度进入的供给分析

本文在分析光纤主干网和本地接入服务市场上电信运营商的供给行为的基础上,首先证明了拥有主干网的运营商愿意租出自己的部分光纤,接着分析证明了上述两市场上使投资更倾向于过度的乘数效应,并进一步证明网络外部性使乘数效应更加明显.旨在对我国电信运营市场发展给出一些参考意见.     

The Extracts of Polygonum cuspidatum Root and Rhizome Block the Entry of SARS-CoV-2 Wild-Type and Omicron Pseudotyped Viruses via Inhibition of the S-Protein and 3CL Protease

COVID-19, resulting from infection by the SARS-CoV-2 virus, caused a contagious pandemic. Even with the current vaccines, there is still an urgent need to develop effective pharmacological treatments against this deadly disease. Here, we show that the water and ethanol extracts of the root and rhizome of Polygonum cuspidatum (Polygoni Cuspidati Rhizoma et Radix), a common Chinese herbal medicine, blocked the entry of wild-type and the omicron variant of the SARS-CoV-2 pseudotyped virus into fibroblasts or zebrafish larvae, with IC₅₀ values ranging from 0.015 to 0.04 mg/mL. The extracts were shown to inhibit various aspects of the pseudovirus entry, including the interaction between the spike protein (S-protein) and the angiotensin-converting enzyme II (ACE2) receptor, and the 3CL protease activity. Out of the chemical compounds tested in this report, gallic acid, a phytochemical in P. cuspidatum, was shown to have a significant anti-viral effect. Therefore, this might be responsible, at least in part, for the anti-viral efficacy of the herbal extract. Together, our data suggest that the extracts of P. cuspidatum inhibit the entry of wild-type and the omicron variant of SARS-CoV-2, and so they could be considered as potent treatments against COVID-19.     

坚硬顶板爆破切顶在沿空留巷中的应用研究

当煤层上方为坚硬顶板时,在工作面回采期间容易出现大面积悬顶,导致巷旁充填体出现大变形破坏,极大威胁采煤安全.为解决这一问题,以某矿1205工作面沿空留巷为工程背景,分析了爆炸围岩裂隙范围和坚硬顶板破断特征,建立了切顶卸压围岩结构力学模型,研究表明,相邻炮孔爆炸后,炮孔间裂隙互相贯穿,降低了顶板强度,同时当切顶角为15°...     

Synthesis and Inhibitory Activity Against Epstein-Barr Virus of Some New 1,2,3,4-Tetrahydropyrimidine-2-thiones

1,2,3,4-Tetrahydropyrimidine-2-thiones 4a–n were synthesized through the reaction of aromatic aldehydes 1a–n , ethyl acetoacetate (2) and thiourea ( 3) . The structures of all newly synthesized heterocyclic compounds elucidated by the use of IR, ¹H NMR, mass spectra, and elemental analyses. The inhibitory activity against the Epstein-Barr Virus early antigen (EBA-VA) of all newly synthesized heterocyclic compounds were evaluated.     

The enormity of the zinc deficiency problem and available solutions; an overview

The societal cost of micronutrient deficiency (MND) or the “hidden hunger” is in millions of dollars/year, reducing the GDP of some countries by as much as 11%. Zn is an important micronutrient for both plants and animals. An estimated 17% of the world population, or around 1.1 billion people, are at the risk of zinc (Zn) deficiency. The deficiency has been related to adverse pregnancy outcomes, stunted growth, premature deaths, immune system dysfunctions, neuro-behavioral disorders, and recently with the failure to recover from COVID-19. These health risks associated with Zn deficiency have compelled FAO and WHO to recommend Zn fortification of diet. Correcting Zn deficiency is a challenge due to several reasons. Close to half of the agricultural soils are Zn deficient, and chemical Zn fertilizers are costly and ineffective. Developing Zn-rich crops through plant breeding and genetic engineering is challenging. Zn-dense diet is costly and cannot be implemented in the low-income region most affected by Zn deficiency. Lack of consensus among regulatory bodies on defining and diagnosing Zn deficiency in plants and Humans. Awareness and other sociocultural issues. Among the most important available solutions are zinc biofortification of the cereal crops, use of zinc biofertilizers, development of Zn-efficient crops with reduced phytate content. The use of Zn supplements, dietary modification, and diversification, especially with fish, are proposed as the most accessible and affordable solutions. Awareness programs in areas suffering the most from Zn deficiency are required. Despite the suggestions from FAO and WHO, global efforts to combat Zn deficiency matching those for combating diseases like HIV are not in place. Coordinated efforts of the international community, especially policy-makers, agricultural scientists, dieticians, physicians, and others, are required to address the issue of hidden hunger.     

新冠疫情对我国信贷风险冲击的定量测算

文章建立了宏观经济传导模型和信贷风险传导模型,根据对GDP的估计,对新型冠状病毒感染肺炎疫情下的2020年全国和若干疫情严重省市的不良贷款率进行了定量测算.假设一季度内疫情得以控制,全年GDP增速下降至5.7％的情景下,预计全国年末不良贷款率约3％,不良贷款余额比2019年增加逾80％,接近2019年国内商业银行贷款损...     

Pharmacophore modelling of structurally unusual diltiazem mimics at L-type calcium channels

The purpose of this theoretical study was to investigate the molecular features of some structurally unusual calcium antagonists with experimentally proved affinity to the diltiazem-binding site at L-type calcium channels. Therefore, sterical and electronic characteristics of cis-/trans-diclofurime, the verapamil-like derivatives McN-5691 and McN-6186 as well as the natural products papaverine, laudanosine, antioquine and tetrandrine were compared with the pharmacophoric requirements detected for classical diltiazem-like derivatives. This yielded a common pharmacophore model for all of these compounds. Based on this model, one single negative molecular electrostatic potential induced by the free electron pairs of the oxime oxygen of trans-diclofurime was detected that might be responsible for the stronger effects compared to the cis isomer. Furthermore, the dual diltiazem- and verapamil-like features of McN-5691 (and McN-6186) as well as the distinct pharmacophoric assignment of the laudanosine enantiomers may be interpreted on a molecular level. Finally, the crucial partial structure of the bis-benzylisoquinoline derivatives antioquine and tetrandrine being responsible for the calcium antagonistic effects could be revealed by superposition on the most active benzothiazepinone derivative 8-methoxydiltiazem. The results obtained for these unusual diltiazem mimics are discussed taking into consideration earlier findings for classical diltiazem-like derivatives.     

Surface-Enhanced Raman Spectroscopy (SERS) for characterization SARS-CoV-2

We used SERS with silver nanoparticles (AgNPs) as the active substrate to develop a, simple, quick, and accurate method for the detection and characterization SARS-CoV-2 without the need for RNA isolation and purification. Inactivated SARS-CoV-2 was used. The SERS signals were more than 10⁵ times enhanced than the normal Raman (NR) spectra. The SERS spectra of SARS-CoV-2 fingerprint revealed pronounced intensity signals of nucleic acids; aromatic amino acid side chains: 1007 cm^?1 (Phe marker), 1095 cm^?1 (CN and PO₂^? markers), 1580 cm^?1 (Tyr, Trp markers). Vibrations of the protein main chain: 1144 cm^?1 (CN and NH₂ markers), 1221 cm^?1 (CN and NH markers), 1270 cm^?1 (NH₂ marker), 1453 cm^?1 (CHCH₂ marker). All of these biomolecules could be adsorbed on the AgNPs surface's dense hot patches. The intensity of the SERS band varied with the concentration of SARS-CoV-2, with a virus detection limit of less than 10³ vp/mL and RSDs of 20 %.     

材料化学课程线上教学初探

2020新年伊始,新冠肺炎突然来袭,为了防止聚集性感染,教育部提出了"停课不停教、停课不停学"的要求。地方普通高校学生的自律性、自觉性及能动性差别十分明显,这样的学情对如何有效开展化学专业的线上教学工作提出了更大的挑战。本文以材料化学课程线上教学为例,介绍地方普通高校化学专业线上教学工作的开展情况。针对教学过程中遇到的各种问题和采用的应对方案,探讨线上教学过程中的注意事项。希望本文能为地方普通高校化学专业线上教学工作提供有益的参考。     

二十面体病毒及其衣壳蛋白质

许多病毒具有二十面体结构。本文对已经发现的各种二十面体病毒进行了分类,分析了二十面体病毒衣壳的结构特征,阐述了二十面体病毒的结构蛋白。