ISSN 0253-2778

CN 34-1054/N

2022 Vol. 52, No. 5

2022-5 Contents
2022, 52(5): 1-2.
2022-5 Abstract
2022, 52(5): 1-2.
Exploring the topological effect of linear and cyclic macroCTAs during polymerization-induced self-assembly (PISA)
Depeng Yin, Wen Xu, Hualong Zhang, Chao Liu, Chunyan Hong
2022, 52(5): 1. doi: 10.52396/JUSTC-2022-0040
Polymerization-induced self-assembly (PISA) is a robust strategy for the syntheses of block copolymer nano-objects with various morphologies. Although PISA has been extensively studied, the use of cyclic macromolecular chain transfer agents (macroCTAs) as the hydrophilic block has not been reported. We explored the effects of macroCTA topology on the polymerization kinetics and morphologies of block copolymer assemblies during reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization. To this end, linear and cyclic poly (ethylene oxide) (PEO) with 4-(4-cyanopentanoic acid) dithiobenzoate (CPADB) groups were synthesized and used as CTAs to mediate the RAFT polymerization of benzyl methacrylate (BzMA) and 2,3,4,5,6-pentafluorostyrene (PFSt) under PISA formulation. Interestingly, the nucleation period of the linear PEO is slightly shorter than that of its cyclic analog, and the cyclic hydrophilic segment leads to a delayed morphological transition during PISA.
Pancyclicity of randomly perturbed digraph
Zelin Ren, Xinmin Hou
2022, 52(5): 2. doi: 10.52396/JUSTC-2021-0208
Dirac’s theorem states that if a graph G on n vertices has a minimum degree of at least $\displaystyle \frac{n}{2}$, then G contains a Hamiltonian cycle. Bohman et al. introduced the random perturbed graph model and proved that for any constant $ \alpha > 0 $ and a graph H with a minimum degree of at least $ \alpha n $, there exists a constant C depending on α such that for any $p \geqslant \dfrac{C}{n}$, $H \cup {G_{n,p}}$ is asymptotically almost surely (a.a.s.) Hamiltonian. In this study, the random perturbed digraph model is considered, and we show that for all $\alpha = \omega \left( {{{\left( {\dfrac{{\log n}}{n}} \right)}^{{\textstyle{1 \over 4}}}}} \right)$ and $d \in \{ 1,2\}$, the union of a digraph on n vertices with a minimum degree of at least $ \alpha n $ and a random d-regular digraph on n vertices is a.a.s. pancyclic. Moreover, a polynomial-time algorithm is proposed to find cycles of any length in such a digraph.
An empirical Bayes method for genetic association analysis using case-control mother-child pair data
Yanan Zhao, Weiqi Yang, Hong Zhang
2022, 52(5): 3. doi: 10.52396/JUSTC-2022-0007
Case-control mother-child pair data are often used to investigate the effects of maternal and child genetic variants and environmental risk factors on obstetric and early life phenotypes. Retrospective likelihood can fully utilize available information such as Mendelian inheritance and conditional independence between maternal environmental risk factors (covariates) and children’s genotype given maternal genotype, thus effectively improving statistical inference. Such a method is robust to some extent if no relationship assumption is imposed between the maternal genotype and covariates. Statistical efficiency can be considerably improved by assuming independence between maternal genotype and covariates, but false-positive findings would be inflated if the independence assumption was violated. In this study, two empirical Bayes (EB) estimators are derived by appropriately weighting the above retrospective-likelihood-based estimators, which intuitively balance the statistical efficiency and robustness. The asymptotic normality of the two EB estimators is established, which can be used to construct confidence intervals and association tests of genetic effects and gene-environment interactions. Simulations and real-data analyses are conducted to demonstrate the performance of our new method.
Worst-case conditional value-at-risk and conditional expected shortfall based on covariance information
Tiantian Mao, Qi Zhao, Qinyu Wu
2022, 52(5): 4. doi: 10.52396/JUSTC-2022-0023
In this paper, we study the worst-case conditional value-at-risk (CoVaR) and conditional expected shortfall (CoES) in a situation where only partial information on the underlying probability distribution is available. In the case of the first two marginal moments are known, the closed-form solution and the value of the worst-case CoVaR and CoES are derived. The worst-case CoVaR and CoES under mean and covariance information are also investigated.
Earth and Space Sciences
An analytical study on early kick detection and well control considerations for casing while drilling technology
Said K. Elsayed, Hany M. Azab, Adel M. Salem
2022, 52(5): 5. doi: 10.52396/JUSTC-2021-0192
Casing while drilling (CwD) technology is designed to reduce drilling time and expenses by improving the wellbore stability, fracture gradient, and formation damage while reducing the exposure time. However, for the purpose well control, the wellbore geometry and volumes differ from those obtained via a conventional drilling technique, thereby requiring a different approach. This study discusses well control principles for CwD operations. It presents a simplified method for evaluating the maximum kick tolerance and allowable well shut-in time for both conventional and CwD techniques using a mathematical model. Preliminary results revealed that the use of CwD leads to an annulus pressure loss three times higher than that observed in the conventional drilling. In addition, the kick tolerance is reduced by 50% and the maximum allowable well shut-in time is reduced by 65%, making an early kick detection system necessary.
Petroleum-contaminated soil extent recorded by δ15N and δ13C of plants and soils
Zhoufeng Wang, Ruijuan Hao, Juan Wang, Yuanyuan Shen, Xiangzhong Li
2022, 52(5): 6. doi: 10.52396/JUSTC-2021-0270
Petroleum contamination in terrestrial environments caused by industrial activities is a significant problem that has received considerable attention. Carbon and nitrogen isotopic compositions (δ13C and δ15N) effectively describe the behavior of plants and soils under petroleum contamination stress. To better understand plant and soil responses to petroleum-contaminated soil, δ13C and δ15N values of the plants (Trifolium repens, Leguminosae with C3 photosynthesis pathway, and Agropyron cristatum with C4 photosynthesis pathway) and the soil samples under one-month exposure to different extents of petroleum contamination were measured. The results showed that petroleum contamination in the soil induced the soil δ15N values to increase and δ13C values to decrease; from 1.9‰ to 3.2‰ and from −23.6‰ to −26.8‰, respectively. However, the δ13C values of Agropyron cristatum decreased from −29.8‰ to −31.6‰, and the δ13C values of Trifolium repens remained relatively stable from −12.6‰ to −13.1‰, indicating that they have different coping strategies under petroleum-contaminated soil conditions. Moreover, the δ15N values of Trifolium repens decreased from 5.6‰ to 0.8‰ near the air δ15N values under petroleum-contaminated soil, which implies that their nitrogen fixation system works to reduce soil petroleum stress. The δ13C and δ15N values of Agropyron cristatum and Trifolium repens reflect changes in the metabolic system when they confront stressful environments. Therefore, stable isotopic compositions are useful proxies for monitoring petroleum-contaminated soil and evaluating the response of plants to petroleum contamination stress.
Deployable boom for Mars Orbiter Magnetometer onboard Tianwen-1
Manming Chen, Zonghao Pan, Tielong Zhang, Xinjun Hao, Yiren Li, Kai Liu, Xin Li, Yuming Wang, Chenglong Shen, Hong Chen, Zhongwang Wang, Xiu Qiang
2022, 52(5): 7. doi: 10.52396/JUSTC-2022-0001
A more than 3 m-long deployable boom is an essential component of the Mars Orbiter Magnetometer (MOMAG) onboard the orbiter of Tianwen-1. The boom was developed to place fluxgate magnetometer (FGM) sensors away from the satellite to reduce the influence of the satellite magnetic field. It was designed as an articulated spring-driven deployable mechanism for single-shot deployment. Functionality, reliability and system constraints are fully considered in the boom design. Mechanical analyses and proof tests show that the boom has sufficient safety margin to withstand environmental conditions, even in the worst cases. After a long voyage from Earth to Mars, the boom was deployed successfully on May 25, 2021. A full deployment was performed in about 4.6 s, sending the two sensors to distances of 3.19 m and 2.29 m respectively, away from the orbiter. After deployment, the field from the orbiter decreased from 1250 nT to less than 6 nT at the sensor mounted at the tip of the boom. The MOMAG boom provides valuable engineering experience for the development of deployable structures stowed for long periods in cold temperatures in space missions.