Synthesis of heliannane skeletons. Facile preparation of (±)-heliannuol D

Heliannuol D is a natural product with a 7,10-heliannane skeleton, isolated from Helianthus annuus. It has been synthesized in eight steps, in good yield, using a new biomimetic method. Key steps were a Fries rearrangement, a Grignard reaction and, finally, a base catalyzed cyclization.     

Triangulated n-manifolds are determined by their [n2] + 1-skeletons

We will reconstruct compact, triangulated n-manifolds—without-boundaries from just their $\text{[}\text{n}\text{2}\text{] + 1}$ skeletons. Therefore, two such manifolds are isomorphic if they have simplicially isomorphic $\text{[}\text{n}\text{2}\text{+ 1}$-skeletons. Furthermore, when n is even, and the $\text{n}\text{2}$-homology group is zero, then the $\text{n}\text{2}$-skeleton is sufficient.     

Mosaic approximations of discrete analogs of Calderón-Zygmund operators

Asymptotic estimates of the form mrA = O(InN · ln ^d ɛ ⁻¹), whered is the dimension of the initial space, for mosaic ranks of discrete analog of Calderón-Zygmund operators are obtained for various mosaic covers. Translated fromMatematicheskie Zametki, Vol. 63, No. 1, pp. 81–94, January, 1998.     

串联系统的可靠性

本文利用侯振挺等人提出的马尔可夫骨架过程理论讨论了串联系统的改进模型的可靠性.     

带干扰的理赔为一般到达的风险模型

本文应用M arkov骨架过程方法,研究了带干扰的理赔为一般到达的保险风险模型,得到了破产时间与破产时刻前后资产盈余的联合分布以及破产时间的分布.     

N-策略休假GI-X／G／1排队系统队长的瞬时分布

本文应用Markov骨架过程理论研究了N-休假策略GI~X/G/1排队系统,并得到了队长的瞬时分布.     

布朗生灭过程及股票价格模型

本文明确地给出了一类布朗生灭过程的定义,讨论了其一维分布、积分泛函的分布和矩, 得到了递推计算公式,然后讨论了布朗生灭过程对股价模型的应用.     

Phase Transition of Triangulated Spherical Surfaces with Elastic Skeletons

A first-order transition is numerically found in a spherical surface model with skeletons, which are linked to each other at junctions. The shape of the triangulated surfaces is maintained by skeletons, which have a one-dimensional bending elasticity characterized by the bending rigidity b, and the surfaces have no two-dimensional bending elasticity except at the junctions. The surfaces swell and become spherical at large b and collapse and crumple at small b. These two phases are separated from each other by the first-order transition. Although both of the surfaces and the skeleton are allowed to self-intersect and, hence, phantom, our results indicate a possible phase transition in biological or artificial membranes whose shape is maintained by cytoskeletons.     

The Quality of Statistical Reporting and Data Presentation in Predatory Dental Journals Was Lower Than in Non-Predatory Journals

Proper peer review and quality of published articles are often regarded as signs of reliable scientific journals. The aim of this study was to compare whether the quality of statistical reporting and data presentation differs among articles published in ‘predatory dental journals’ and in other dental journals. We evaluated 50 articles published in ‘predatory open access (OA) journals’ and 100 clinical trials published in legitimate dental journals between 2019 and 2020. The quality of statistical reporting and data presentation of each paper was assessed on a scale from 0 (poor) to 10 (high). The mean (SD) quality score of the statistical reporting and data presentation was 2.5 (1.4) for the predatory OA journals, 4.8 (1.8) for the legitimate OA journals, and 5.6 (1.8) for the more visible dental journals. The mean values differed significantly (p < 0.001). The quality of statistical reporting of clinical studies published in predatory journals was found to be lower than in open access and highly cited journals. This difference in quality is a wake-up call to consume study results critically. Poor statistical reporting indicates wider general lower quality in publications where the authors and journals are less likely to be critiqued by peer review.     

Spherical coxeter groups and hyperelliptic 3-manifolds

Reflection groups of Coxeter polyhedra in three-dimensional Thurston geometries are examined. For a wide class of Coxeter groups, the existence of subgroups of finite index that uniformize hyperelliptic 3-manifolds is established. Translated fromMatematicheskie Zametki, Vol. 66, No. 2, pp. 173–177, August, 1999.