第12届全国大学生化学实验邀请赛无机及分析化学实验试题解析

介绍了第12届全国大学生化学实验邀请赛无机及分析化学实验操作试题的命题思路,总结实验成绩,分析实验操作考试中存在的主要问题。

Eigenvalue and stability analysis for transverse vibrations of axially noving strings based on Hamiltonian dynamics

Hamiltonian 动力学被采用为移动绳的向轴的方向的横向的颤动解决特征值问题。与明确的 Hamiltonian 功能，免费颤动的正则转变被导出。非退化的形式的功能被获得通过一线性， symplectic 特征值分析，和模式的 symplectic 类型 orthogonality 条件被导出。横向的运动的稳定性借助于分析特征值和他们的分叉被检验，特别为与临界速率搬运的绳。绳的运动不由于在特征值对之间的弱相互作用在临界速率拥有分叉不稳定性，这被指出。扩大定理与非退化的形式的功能被使用解决排水量反应到免费、强迫的颤动。当库为解决线性、非线性的颤动问题工作，形式的函数能被使用，这被表明。

Comparative study of the stoichiometric characteristics of karst and non-karst forests in Guizhou, China

Carbon (C), nitrogen (N), and phosphorous (P) levels and their stoichiometry in plant components (leaves, branch trunks, roots) of trees in a karst forest and non-karst forest are compared. The results show that the C contents, C:N and C:P ratios of dominant species in the karst forest were lower than those in the non-karst forest, but the N and P and the N:P ratio were higher;C:N:P ratios in plant organs of trees in the karst forest were in the order of trunks>roots>branches>leaves. However, C:N:P ratio in the non-karst forest trees were trunks>branches>roots>leaves. Moreover, ratio of C:N:P in trunks was highest and lowest in leaves in both forests. In non-karst forest trees, N:P was in the order of leaves> roots>branches>trunks. There were no significant differences in the ratio of N:P in different plant components of trees in the karst forest. However, in karst and non-karst forest trees, the ratio of N:P in leaves was highest;positive correlations between N and P contents, and N and N:P ratios were observed in both karst and non-karst forests (p<0.001). Negative correlations between P and N:P ratios (p<0.05) were observed in karst forest trees, while positive correlations were observed in non-karst forest trees.

FEM and EFG Quasi-Static Explicit Buckling Analysis for Thin-Walled Members

The quasi-static explicit finite element method (FEM) and element free Galerkin (EFG) method are applied to trace the post-buckling equilibrium path of thin-walled members in this paper. The factors that primarily control the explicit buckling solutions, such as the computation time, loading function and dynamic relaxation, are investigated and suggested for the buckling analysis of thin-walled members. Three examples of different buckling modes, namely snap-through, overall and local buckling, are studied based on the implicit FEM, quasi-static explicit FEM and EFG method via the commercial software LS-DYNA. The convergence rate and accuracy of the explicit methods are compared with the conventional implicit arc-length method. It is drawn that EFG quasi-static explicit buckling analysis presents the same accurate results as implicit finite element solution, but is without convergence problem and of less-consumption of computing time than FEM.

Genetic Characterization of Two Human Cases Infected with the Avian Influenza A(H5N6)Viruses—Guangxi Zhuang Autonomous Region,China,2021

Summary What is known about this topic?H5N6 has replaced H5N1 as a dominant avian influenza virus(AIV)subtype in southern China.The increasing genetic diversity and geographical distribution of H5N6 pose a serious threat to the poultry industry and human health.What is added by this report?A total of 2 cases of H5N6 that occurred from February 2021 to July 2021 in Guangxi.

Effect of different doping elements on performance of Ce-Mn/TiO_(2)catalyst for low temperature denitration

Sm and Ho were doped in Ce-Mn/TiO_(2)catalyst respectively to enhance its denitration performance at low temperature.X-ray diffraction(XRD),N2adsorption-desorption,X-ray photoelectron spectroscopy(XPS),NH3-temperature programmed desorption(NH3-TPD),H2-temperature programmed reduction(H2-TPR)and in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)techniques were used to analyze the structure and performance of catalysts.The results demonstrate that Ho doping increases the amount of acid sites and improves low temperature redox property of Ce-Mn/TiO_(2),which lead to excellent DeNOxperformance of Ho-Ce-Mn/TiO_(2)in the whole reaction temperature range.Sm doping results in decline of redox property,but it is beneficial to increasing the acid sites of Ce-Mn/TiO_(2).The increased surface acid sites and moderate oxidative ability impart Sm-Ce-Mn/TiO_(2)higher denitration activity and N2selectivity at temperature above 150℃.Lewis acid sites and redox property are the main factors affecting the activity of catalysts.Doping of Ho and Sm both improves sulfur resistance performance of Ce-Mn/TiO_(2)by inhibiting the adsorption of SO_(2)and formation of sulfate.Ce-Mn/TiO_(2)modified by Ho shows better sulfur resistance than that doped with Sm because of its more surface acid sites.

Reduced-Order Observer-Based LQR Controller Design for Rotary Inverted Pendulum

The Rotary Inverted Pendulum(RIP)is a widely used underactuated mechanical system in various applications such as bipedal robots and skyscraper stabilization where attitude control presents a significant challenge.Despite the implementation of various control strategies to maintain equilibrium,optimally tuning control gains to effectively mitigate uncertain nonlinearities in system dynamics remains elusive.Existing methods frequently rely on extensive experimental data or the designer’s expertise,presenting a notable drawback.This paper proposes a novel tracking control approach for RIP,utilizing a Linear Quadratic Regulator(LQR)in combination with a reduced-order observer.Initially,the RIP system is mathematically modeled using the Newton-Euler-Lagrange method.Subsequently,a composite controller is devised that integrates an LQR for generating nominal control signals and a reduced-order observer for reconstructing unmeasured states.This approach enhances the controller’s robustness by eliminating differential terms from the observer,thereby attenuating unknown disturbances.Thorough numerical simulations and experimental evaluations demonstrate the system’s capability to maintain balance below50Hz and achieve precise tracking below1.4 rad,validating the effectiveness of the proposed control scheme.

塑料薄膜包裹预防新生儿低体温有效性及安全性的系统评价

目的系统评价塑料薄膜包裹对新生儿保暖效果的有效性及安全性,以期为临床新生儿保暖措施的选择提供依据。方法计算机检索Cochrane Library、Pub Med、Scopus、中国生物医学文献数据库、万方、维普、中国学术期刊全文数据库等国内外数据库中有关塑料薄膜包裹应用于新生儿保暖的随机对照研究。对所得文献依据纳入与排除标准进行筛查,提取资料,评价文献质量,采用Rev Man 5.2软件进行Meta分析。结果最终纳入16项随机对照试验,包括2 836例研究对象。Meta分析结果显示,塑料薄膜包裹组早产儿进入NICU时低体温发生率[RR=0.71,95%CI (0.64,0.79),P<0.01]、进入NICU时体温[MD=0.60,95%CI (0.47,0.72),P<0.01]、进入NICU时发热发生率[RR=4.09,95%CI(2.12,7.88),P<0.01]与常规护理组相比,差异具有统计学意义;Ⅲ度或Ⅳ度脑室内出血发生率[RR=0.92,95%CI(0.65,1.32),P=0.660]、出院前病死率[RR=0.75,95%CI(0.53,1.08),P=0.120]与常规护理组相比,差异无统计学意义。结论塑料薄膜包裹能减少早产儿进入NICU时低体温的发生率,提高早产儿进入NICU时的体温,可以作为一种有效的早产儿保暖方法,但有引起发热的风险;塑料薄膜包裹不能降低早产儿Ⅲ度或Ⅳ度脑室内出血发生率及出院前病死率。

Mechanisms of resistance to EGFR tyrosine kinase inhibitors

Since the discovery that non-small cell lung cancer(NSCLC) is driven by epidermal growth factor receptor(EGFR) mutations, the EGFR tyrosine kinase inhibitors(EGFR-TKIs, e.g., ge fi tinib and elrotinib) have been effectively used for clinical treatment. However, patients eventually develop drug resistance. Resistance to EGFR-TKIs is inevitable due to various mechanisms, such as the secondary mutation(T790M), activation of alternative pathways(c-Met, HGF, AXL), aberrance of the downstream pathways(K-RAS mutations, loss of PTEN), impairment of the EGFR-TKIs-mediated apoptosis pathway(BCL2-like 11/BIM deletion polymorphism), histologic transformation, ATP binding cassette(ABC) transporter effusion, etc. Here we review and summarize the known resistant mechanisms to EGFR-TKIs and provide potential targets for development of new therapeutic strategies.

核纤层蛋白B1的功能及其在神经系统疾病和肿瘤中的研究新进展

核纤层蛋白B1 (Lamin B1)是核纤层蛋白家族重要成员之一,其主要功能在于维持细胞核骨架完整性,并通过影响染色体分布、基因表达及DNA损伤修复等参与细胞的增殖和衰老。其表达异常与多种疾病有关,如神经系统疾病(神经管畸形,ADLD)及肿瘤(胰腺癌)等,是潜在的药物靶点和肿瘤标志物。对Lamin B1功能的深入研究,将有助于对相关神经系统疾病和肿瘤发生发展的分子机制的了解并为治疗靶点研究提供新方向。

Role of endogenous hormones,glumes,endosperm and temperature on germination of Leymus chinensis(Poaceae)seeds during development

Aims Leymus chinensis is an original dominant plant in the Songnen grassland,and it has great value for restoration of severely degraded land.However,seeds are dormant,and low germination percentage is a problem for restoring L.chinensis grassland.The mechanism of seed dormancy is not been well understood.The primary aims of the present study were to investigate the dormancy mechanism of L.chinensis seeds(caryopses)with reference to the role of embryo-covering layers,endogenous hormones and temperature.Methods Changes in concentration of the endogenous hormones GA3,indoleacetic acid(IAA),zeatin riboside(ZR)and abscisic acid(ABA)in L.chinensis seeds fromanthesis to maturity weremeasured by the enzymelinked immunosorbent assay method.Germination at different stages of maturity were tested at 16/28
C,5/28
C and 5/35
C for intact seeds with glumes(control),intact seeds with glumes removed(nakedwhole seeds)and intact seeds with glumes and one-half of the endosperm removed(naked-half seeds).Important Findings Of the four endogenous hormones monitored,only the concentration of ZR differed significantly between the beginning and the end of seed development(increased);the GA3/ABA ratio also did not differ.Rank of germination percentage of control at the three temperature regimens was 5/28
C>16/28
C>5/35
C.Germination percentage of the naked-half seeds reached 100%under the three temperature regimens.We concluded that dormancy of L.chinensis seeds is not mainly controlled by endogenous hormones.Germination temperature,mechanical resistance of glumes and inhibition of endosperm are the main factors controlling dormancy and germination of L.chinensis seeds.

Identifying Influencing Factors for Data Transactions:A Case Study from Shanghai Data Exchange

In the age of artificial intelligence,firms'internal data are increasingly valuable when merged with each other for inter-firm analysis and predictions.However,the inter-firm data transactions represent a novel challenge on pricing due to the complex nature of data,such as quality information asymmetry,lack of pricing standards,and the negligible marginal cost.This paper conducts a case study at Shanghai Data Exchange to explore the factors that can facilitate the data transactions between buyers and providers.We use interview transcripts from 18 participating firms to construct our three theoretical dimensions:increasing the perceived value,mitigating the cost,and improving the market design.We then browse through 18 factors to assess their value for further improvements.The managerial implications are also discussed.

Chemical characteristics of road dust PM2.5 fraction in oasis cities at the margin of Tarim Basin

In order to understand the compositions characteristics of particulate matter with aerodynamic diameter less than 2.5μm(PM2.5)fraction in road dust(RD2.5)of oasis cities on the edge of Tarim Basin,30 road dust(RD)samples were collected in Kashi,Cele,and Yutian in the spring,2018,and RD2.5 was collected using the resuspension approach.Eight watersoluble ions,39 trace elements and 8 fractions of carbon-containing species in PM2.5 were analyzed.Ca2+and Ca were the most abundant ions and elements in RD2.5(7.1%and 9.5%).Cl-in RD2.5 was affected not only by attributed to saline-alkali soils in oasis cities of the Tarim Basin and dust from Taklimakan Desert but also by human activities.Moreover,the organic carbon/elemental carbon(OC/EC)ratio indicated that carbon components in RD2.5in Cele town mainly come from fossil fuel combustion,while those in Yutian and Kashi mainly come from biomass combustion.It is noteworthy that high Ca in RD2.5 was seriously affected by anthropogenic emissions,and high Na and K contents in RD2.5 could be derived from soil and desert dust.It was estimated that Cd,Tl,Sn and Cr were emitted from anthropogenic emissions using the enrichment factor.The coefficients of divergence(cOD)result indicated that the influence of local emission on road dust emission is greater than that of long-distance transmission.This study is the first time to comprehensively analyze the chemical characteristics of road dust in oasis cities,and the results provides the sources of road dust at the margin of Tarim Basin.

Evaluation of Epstein-Barr Virus Salivary Shedding in HIV/AIDS Patients and HAART Use: A Retrospective Cohort Study

Little data is available on the evaluation of the occurrence rates of Epstein-Barr virus(EBV) in saliva and relationship with highly active antiretroviral therapy(HAART) use in HIV/AIDS patients in China. We conducted a retrospective cohort study of EBV serological tests for HIV/AIDS patients who were treated in the hospitals for infectious diseases in Wuxi and Shanghai, China from May 2016 to April 2017. The EBV-seropositive samples were identified by ELISA. EBV-specific primers and probes were used for the quantitative detection of viral DNA from saliva via quantitative real-time polymerase chain reaction. CD4 cell counts of the HIV/AIDS patients were detected by a flow cytometry. A total of 372 HIV/AIDS patients were ultimately selected and categorized for this retrospective cohort study. For EBV IgG and IgM, the HIV/AIDS HAART use(H) and non-HAART use(NH) groups had significantly higher seropositive rates than the HIV-negative control group. The HIV/AIDS(NH) group had the highest seropositive rate(IgG, 94.27%; IgM, 68.98%) and the highest incidence of EBV reactivation or infection. For salivary EBV DNA-positive rates and quantities, the HIV/AIDS(H)(73.69%) and the HIV/AIDS(NH)(100%) groups showed significantly higher values than the HIV-negative control group(35.79%,[ twofold). Further, the salivary EBV DNA-negative population had significantly higher CD4 cell counts than the EBV DNA-positive population in the HIV/AIDS(H) group and the HIV/AIDS(NH) groups. Thus, HAART use is beneficial in decreasing the EBV salivary shedding in HIV/AIDS patients and indirectly decreases EBV transmission risk.

Toward a research framework to conceptualize data as a factor of production:The data marketplace perspective

The widespread use of machine learning techniques and artificial intelligence algorithms has highlighted the strategic role of data.To acquire data for training algorithms and eventually empowering the digital transformation,data marketplaces are often required to support and coordinate cross-organizational data transactions.However,the prior industry practices have suggested that the transaction costs in the data marketplaces are severely high,and the supporting infrastructure is far from mature.This paper proposes a data attributes-affected data exchange(DADE)conceptual model to understand the challenges and directions for developing data marketplaces.Specifically,our model framework is built upon two dimensions,data lifecycle maturity and data asset specificity.Based on the DADE model,we propose four approaches for developing data marketplaces and discuss future research directions with an overview of computational methods as potential technical solutions.

Rational design of nanocarriers for mitochondria-targeted drug delivery

Well-developed mitochondria-targeted nanocarriers for function regulation are highly desirable.Numerous studies have been conducted on the treatment of mitochondria-related diseases;however,further improvements are required to develop more effective drug delivery methods.Herein,we comprehensively introduce recent developments progress in rational design of mitochondria-targeted nanocarriers,and discuss the different strategies of available nanocarriers for targeting mitochondria.We also highlight the advantages and disadvantages of various carrier systems that are currently in use.Finally,perspective on new generation for mitochondria-targeted delivery systems in the emerging area of drug-based therapeutics is also discussed.

Reflectance transformation imaging of 3D detection for subtle traces

This paper reports a detection method of two-dimensional(2 D) enhancement and three-dimensional(3 D) reconstruction for subtle traces with reflectance transformation imaging, which can effectively locate the trace area of interest and extract the normal data of this area directly. In millimeter-and micron-scale traces, during 3 D construction, we presented a method of data screening, conversion, and amplification, which can successfully suppress noise, improve surface and edge quality,and enhance 3 D effect and contrast. The method not only captures 2 D and 3 D morphologies of traces clearly but also obtains the sizes of these traces.

Application of reflectance transformation imaging for the display of handwriting traces

In our Letter, two kinds of handwriting traces, colored and colorless, are studied by means of reflectance transformation imaging. The illumination direction and rendering mode can be changed alternatively to obtain two-dimensional and three-dimensional details of the traces that are not recognized easily by naked eyes.Furthermore, an objective evaluation method without reference is applied to evaluate the reconstructed images,which provides a basis for setting the illumination direction and rendering mode. Therefore, the handwriting trace information including the written content, the writing features, and the stroke order features can be obtained objectively and accurately.