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A highly enantioselective cyclopropanation to synthesize pyrimidine-substituted diester D–A cyclopropanes is reported. Various N1-vinylpyrimidines react well with phenyliodonium ylides, delivering chiral cyclopropanes in up to 97% yield with up to 99% ee. Through simple [3+2] annulation with benzaldehyde or ethyl glyoxylate, different chiral pyrimidine nucleoside analogues with a sugar ring could be obtained. [ABSTRACT FROM AUTHOR]

The 6RUS parallel manipulator is a highly versatile and widely used robotic mechanism with six degrees of freedom. Its intricate kinematic structure and its capability to perform complex motion tasks have garnered significant research interest in recent years. The kinematic analysis of the 6RUS mechanism plays a crucial role in understanding its operational characteristics and optimizing its performance for various applications. In this paper, we present a state-of-the-art kinematic algorithm for the 6RUS parallel manipulator. Our algorithm is aimed at addressing the challenges associated with accurately determining the pose and motion of the end-effector relative to the base, considering the complexity of the mechanism's architecture. By leveraging advanced mathematical modeling techniques and utilizing efficient computational algorithms, our proposed algorithm offers improved accuracy, efficiency, and robustness in determining the kinematic parameters of the 6RUS mechanism. The key contributions of this work include the development of a comprehensive forward and inverse kinematic model for the 6RUS parallel manipulator, incorporating the effects of joint constraints, singularities, and workspace limitations. We also present a detailed analysis of the algorithm's performance in comparison to existing approaches, demonstrating its superiority in terms of computational efficiency and accuracy. The proposed kinematic algorithm holds significant potential for enhancing the design, control, and trajectory planning of 6RUS parallel manipulators. It provides a solid foundation for advanced applications such as robotic surgery, industrial automation, and virtual reality systems. The results presented in this paper contribute to the growing body of knowledge in parallel manipulator research and pave the way for future developments in the field. [ABSTRACT FROM AUTHOR]

Di-isononyl phthalate esters (DINPs) are endocrine-disrupting chemicals and have replaced di(2-ethylhexyl) phthalate (DEHP) as the major plasticizer for poly(vinyl chloride) (PVC) products in recent years. Exposure marker discovery of DINPs is crucial, because of their high potential for human exposure and toxicity. Here, we propose an alternative approach for tracing signals derived from stable isotope-labeled precursors with varied labeling ratios to efficiently filter probable metabolite signals. The statistical process, which involves a signal mining algorithm with isotope tracing (SMAIT), has effectively filtered 13 probable DINP metabolite signals out of the 8867 peaks in the LC-MS data obtained from incubated stable isotope-labeled precursors with liver enzymes. Seven of the 13 probable metabolite signals were confirmed as DINP structure-related metabolites by preliminary MS/MS analyses. These 7 structure-related metabolite signals were validated as effective DINP exposure markers, using urine samples collected from DINP-administered rats without time-consuming comprehensive structure identification. We propose that the 7 identified possible DINP metabolite signals of m/z 279.1, 293.1, 305.1, 307.1, 321.1, 365.1, and 375.1 are potential markers for DINP exposure and should be investigated further. The integrated approach described here can efficiently, and systematically, filter probable metabolite signals from a complex LC-MS dataset for toxic exposure marker discovery. It is a relatively low-cost/rapid workflow for exposure marker discovery. [ABSTRACT FROM AUTHOR]

• Chiral cyclopropyl pyrimidine carbocyclic nucleoside bearing a quaternary center. • Organocatalytic asymmetric Michael-initiated cyclopropanation. • Cyclopropyl pyrimidine carbocyclic nucleoside with axis chirality phenomenon. An efficient method to construct chiral cyclopropyl pyrimidine carbocyclic nucleoside analogues bearing a quaternary center was developed via asymmetric Michael-initiated cyclopropanation. The axis chirality was observed in cyclopropyl pyrimidine carbocyclic nucleoside analogues for the first time, which was caused by the rotationally restricted N C bond in N -COPh moiety. Using (DHQD) 2 AQN as the organocatalyst, diverse cyclopropyl pyrimidine carbocyclic nucleoside analogues were generated in 76–93% yields and 73–96% ee. [ABSTRACT FROM AUTHOR]

The investigation of irradiation sensitivity of electron spin resonance (ESR) centers is a significant part of the study of ESR signal characteristics and helps to gain insight into the physical mechanisms of paramagnetic centers. In this study, we have observed and compared the irradiation sensitivity characteristics of ESR centers under high-temperature baking in natural conditions by lava flow. Results show that the irradiation sensitivity of the Al and Ti–Li centers increases with the baking temperature, while the irradiation sensitivity of the Ti–H center increases first (up to ∼500 °C) and then decreases with temperature. Moreover, the ESR intensity of the Ti center is more strongly dependent on the annealing history of the samples than the Al center. In addition, from the results of the heating experiment, after heating above 1000 °C, additional irradiation does not produce new Ti–H signals, which probably indicates that the paleo-temperature of the lava flow in Yujiazhai area did not exceed 1000 °C. • The irradiation sensitivity of quartz ESR centers in lacustrine sediments under baking of lava flow were investigated. • The intensity of the Ti center are more strongly dependent on the annealing history of the samples than the Al center. • The paleo-temperature of the lava flow in Yujiazhai area may did not exceed 1000 °C. [ABSTRACT FROM AUTHOR]

Withdifferent transition metal (TM) complexes as structure-directingagents or structure-building units, a series of new mercury thioantimonateswith abundant architectures ranging from one-dimensional (1D) ribbonsto two-dimensional (2D) layers have been solvothermally synthesizedand structurally characterized. Compounds [Co(en)3]Hg2Sb2S6(1) (en = ethylenediamine)and [Ni(1,2-dap)3]2HgSb3S7Cl (2, 1,2-dap = 1,2-diaminopropane) containa discrete 2D [Hg2Sb2S6]n2n–layer and1D [HgSb3S7]n3n–chain, respectively. Compounds[Ni(1,2-dap)3]HgSb2S5(3) and [Mn(dien)2]HgSb2S5(4, dien = diethylenetriamine) feature distinct 2D[HgSb2S5]n2n–layer and 1D [HgSb2S5]n2n–ribbon, respectively, whereas the 1D [HgSb2S5]n2n–chains are attached by [TM(tren)]2+complexes via TM–Sbonds to form 1D {[TM(tren)]HgSb2S5}nribbons in compounds [TM(tren)]HgSb2S5(TM = Mn (5), Fe (6), Co(7), tren = tris(2-aminoethyl)amine). Compounds [TM(dien)2]Hg3Sb4S10(TM = Mn (8), Co(9), Ni(10)) feature 2D [Hg3Sb4S10]n2n–anionic layers separated by[TM(dien)2]2+cations. The most interestingstructural feature of these compounds is the presence of three differenttypes of coordination environments of Hg centers including linear[HgS2] unit, [HgS3] triangle, and [HgS4] tetrahedron. The optical properties and thermal stabilities ofthe title compounds were studied by UV–vis spectra and thernogravimetricanalyses, respectively. The photocatalytic experiments indicated that 3, 4, and 10were able to degraderhodamine B (RhB) under visible irradiation. [ABSTRACT FROM AUTHOR]

Abstract: Full-length hepatitis B virus (HBV) reverse transcriptase (RT) sequences were amplified and sequenced among 192 nucleos(t)ide analogue (NA)-naïve Chinese patients with chronic hepatitis B. Deduced amino acids (AAs) at 42 previously reported potential NA resistance (NAr) mutation positions in RT region were analyzed. Patients were found with either B-genotype (28.65%) or C-genotype (71.35%) infections. Rt53, rt91, rt124, rt134, rt221, rt224, rt238 and rt256 were identified as B- and C-genotype-dependent polymorphic AA positions. AA substitutions at 11 classical NAr mutation positions, i.e. rt80, rt169, rt173, rt180, rt181, rt184, rt194, rt202, rt204, rt236 and rt250, were not detected. However, potential NAr mutations were found in 30.73% (59/192) isolates, which involved 18 positions including rt53, rt207, rt229, rt238 and rt256, etc. The concomitant AA changes of HBsAg occurred in 16.67% (32/192) isolates including sG145R mutation. One-third of mutation positions were located in functional RT domains (e.g. rt207 and rt233), A–B interdomains (overlapping HBsAg ‘a’ determinant and showing most concomitant immune-associated mutations) and non-A–B interdomains (e.g. rt191 and rt213), respectively. Genotypes B and C each showed several preferred positions to mutate. These results might provide insights into understanding the evolution and selection basis of NAr HBV strains under antiviral therapy. [Copyright &y& Elsevier]

Abstract: In the present study, using the single fiber recording technique, we found that BmK I, the main toxic component in scorpion Buthus martensi Karsch (BmK) venom, induced dramatic increase in excitability of rapidly adapting (RA) and type I slowly adapting (SAI) low threshold mechanical A fibers of rat. Five micrograms BmK I (691nmol, in 10μl saline) administrated to the receptive fields induced spontaneous activity in 80% of RA and SAI fibers, increased the response to 10g–10s stimulation at about 20 times and altered the firing pattern to burst mode with maximal NS (number of spikes in burst) averaging from all fibers studied as many as 59. The increase in the excitability of RA and SAI fibers did not recover completely in 2h. Our finding suggests that the gigantic abnormal activity in low threshold mechanical A fibers is involved in BmK scorpion sting pain, and the experimental model of BmK scorpion sting pain can be used to study A-fiber related central pathway which is important for relief of refractory neuropathic pain likewise. [Copyright &y& Elsevier]