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101.
Slawomir Cynk 《代数通讯》2013,41(8):4097-4102
Let B be a surface of even degree d in P3 with nodes as the only singular points. In [1] Clemens proved that the topology of the small resolution of the double covering of P3 branched along B depends not only on the number of nodes but also on the so-called defect, a non-negative integer describing their configuration. The aim of this note is to give an elementary proof of the Clemens. result and to present some geometric interpretation of defect. 相似文献
102.
N. Senthilkumar Y. S. Somannavar Brajesh Kumar Sinha G. K. A. S. S. Narayan Ramesh Dandala 《合成通讯》2013,43(2):268-276
A simple synthetic route for active metabolites of carvedilol is reported. The metabolites 4′-hydroxycarvedilol and 5′-hydroxycarvedilol have exhibited high activity for β-blockade. We have disclosed syntheses of 4′-hydroxycarvedilol and 5′-hydroxycarvedilol from commercially available vanillin and isovanillin, respectively. 相似文献
103.
Dr. Philipp Holtkamp Dario Poier Beate Neumann Dr. Hans-Georg Stammler Prof. Dr. Norbert W. Mitzel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(11):3793-3798
The reactivity of the geminal frustrated Lewis pair (FLP) (F5C2)3SnCH2P(tBu)2 ( 1 ) was explored by reacting it with a variety of small molecules (PhOCN, PhNCS, PhCCH, tBuCCH, H3CC(O)CH=CH2, Ph[C(O)]2Ph, PhN=NPh and Me3SiCHN2), featuring polar or non-polar multiple bonds and/or represent α,β-unsaturated systems. While most adducts are formed readily, the binding of azobenzene requires UV-induced photoisomerization, which results in the highly selective complexation of cis-azobenzene. In the case of benzil, the reaction does not lead to the expected 1,2- or 1,4-addition products, but to the non-stereoselective (tBu)2PCH2-transfer to a prochiral keto function of benzil. All adducts of 1 were characterised by means of multinuclear NMR spectroscopy, elemental analyses and X-ray diffraction experiments. 相似文献
104.
Haichao Zhu Meihua Liu Haiyan Li Ting Guan Qi Zhang Yang Chen Yingxiang Liu Rolf R. Hartmann Lina Yin Qingzhong Hu 《中国化学快报》2021,32(7):2327-2332
Exorbitant aldosterone is closely associated with various severe diseases, including congestive heart failure and chronic kidney disease. As aldosterone synthase is the pivotal enzyme in aldosterone biosynthesis, its inhibition constitutes a promising treatment for these diseases. Via a structure-based approach, a series of pyridyl substituted 3,4-dihydrobenzo[f][1,4]oxazepin-5(2H)-ones were designed as inhibitors of aldosterone synthase. Six compounds (5j, 5l, 5m 5w, 5x and 5y) distinguished themselves with potent inhibition (IC50 <100 nmol/L) and high selectivity over homogenous 11β-hydroxylase. As the most promising compound, 5x exhibited an IC50 of 12 nmol/L and an excellent selectivity factor (SF) of 157, which are both superior to those of the reference fadrazole (IC50 = 21 nmol/L, SF = 7). Importantly, 5x showed no inhibition against steroidogenic CYP17, CYP19 and a panel of hepatic CYP enzymes indicating an outstanding safety profile. As it manifested satisfactory pharmacokinetic properties in rats, compound 5x was considered as a drug candidate for further development. 相似文献
105.
A modular attachment mechanism of software network evolution is presented in this paper. Compared with the previous models, our treatment of object-oriented software system as a network of modularity is inherently more realistic. To acquire incoming and outgoing links in directed networks when new nodes attach to the existing network, a new definition of asymmetric probabilities is given. Based on this, modular attachment instead of single node attachment in the previous models is then adopted. The proposed mechanism is demonstrated to be able to generate networks with features of power-law, small-world, and modularity, which represents more realistic properties of actual software networks. This work therefore contributes to a more accurate understanding of the evolutionary mechanism of software systems. What is more, explorations of the effects of various software development principles on the structure of software systems have been carried out, which are expected to be beneficial to the software engineering practices. 相似文献
106.
Dr. Erin N. Hancock Prof. M. Kevin Brown 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(2):565-576
The ladderane family of natural products are well known for their linearly concatenated cyclobutane skeletal structure. Owing to their unique carbocyclic framework, several chemical syntheses have been reported since their discovery in 2002. The focus of this review is to showcase the novel tactics that have been used to generate the ladderane core and the challenges that are associated with the synthesis of these unusual and complex natural products. 相似文献
107.
肿瘤的缺氧微环境与其增殖、分化、血管生成、能量代谢、耐药性的发生以及患者预后状况密切相关。缺氧诱导因子1(Hypoxia-inducible factor 1, HIF-1)是细胞适应缺氧环境的重要转录因子和调控蛋白,通过调控下游靶基因如EPO、VEGF、GLUT等的表达,促进血管新生及有氧糖酵解以适应缺氧的环境,进而影响肿瘤细胞代谢、血管生成和肿瘤转移等。因此,开发以HIF-1为靶标的小分子抑制剂药物有望成为一种有效的肿瘤治疗方法。本文就HIF-1小分子抑制剂在肿瘤学研究中的进展进行综述,旨在为靶向HIF-1抗肿瘤药物的研发提供新思路。 相似文献
108.
The formation of large size clusters,and/or their relative motion as a possible excitation mode,are sugge sted to be closely related to the origin of deformation in specific cases,namely the case of two doubly-magic clusters or two clusters with nearby characterization.New lifetime data in N=Z ~(76)Sr and ~(80)Zr leading to large B(E2) values are reproduced consistently and well within this approach,along with data for a few neighboring N≈Z nuclei.These results are compared to previous studies of ~(32)S and ~(20)Ne and all of them support the ideas of the large-scale cluster approach. 相似文献
109.
Leandro F. Gil‐Silva Raquel Santamaría‐Fernández Prof. Dr. Armando Navarro‐Vázquez Prof. Roberto R. Gil 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(2):472-476
A new DMSO‐compatible aligning gel based on cross‐linked poly(2‐hydroxylethyl methacrylate) (poly‐HEMA) has been developed. Due to a significant difference in bulk magnetic susceptibility between the DMSO inside and outside the gel, it is possible to simultaneously collect isotropic and anisotropic NMR data, such as residual dipolar couplings (RDC), in the same NMR tube. RDC‐assisted structural analysis of menthol and the alkaloid retrorsine is reported as proof of concept. 相似文献
110.
Small molecule‐mediated glass transition of acrylic copolymers: Effect of hydrogen bonding strength on glass transition temperature 下载免费PDF全文
Chongyang Liu Xiaotong Yin Yu Lin Aiguo Guan Guozhang Wu 《Journal of Polymer Science.Polymer Physics》2015,53(6):400-408
Poly(styrene‐co‐ethyl acrylate) [P(St‐co‐EA)] with different ratios of St/EA was mixed with the small molecule 4,4′‐thio‐bis(6‐tert‐butyl‐m‐methyl phenol) (AO300) to investigate the influence of hydrogen bonding strength on the glass transition behavior. The glass transition temperature (Tg) linearly increased after adding AO300, and the slope value decreased with increased St/EA ratio. All lines could be extended to 62 °C, demonstrating that Tg of the small molecule in situ detected by the polymer chain was much higher than that by small molecule itself (29 °C). Fourier transform infrared spectroscopy analysis showed that the small molecules began to be self‐associated at a concentration where the hydrogen bonded carbonyl ratio of the bulk polymer was approximately 0.5 and irrespective of the St/EA ratio. Above the critical loading, the mixture's Tg negatively deviated from the linearly extended lines because of self‐association of the small molecules. The apparent Tg of AO300 was found to strongly depend on intermolecular hydrogen bonding number and strength. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 400–408 相似文献