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2002年,我在中国科学院研究生院开设了一门面向全院的公共选修新课程——“宇宙与生命”。该课本来是为了介绍一些有关宇宙与生命的基础知识和精美图片,但是数年来许多同学的提问和与我的讨论,促使我思考了更广泛和更深层次的一些问题:宇宙为何如此?宇宙与生命之间的关系是什么?我们的宇宙特殊吗?当今前沿科学怎么认识我们的宇宙和其中的生命?开课6年以来,该课深受同学们的欢迎。通过数年的备课、教学和思考,除了解到科学界对这些问题的激烈争论外,还感觉到我自己也产生了一些比较独特的看法。应《现代物理知识》的邀请,我特地对该课和我的一些独特看法加以总结,为该杂志写几篇介绍文章,以便抛砖引玉,启发读者获得更深入的见解。以下是我的各篇文章标题:万物之图,万物之数,宇宙之大,生命之难,调控万物,核之精细,质量的生成,宇宙的格局、演变与未来,从弦与膜的世界到我们的宇宙——未解之谜,我们宇宙的中心角色——高级生命。 相似文献
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经北京声学学会理事会研究,决定于1999年10-11月在北京召开北京声学学会第五届学术年会。会议论文将出专集;并根据《杜连耀声学奖》评审原则评选出优秀论文予以奖励。奖金由“杜连耀声学基金”支付。一等奖 1名 奖金;2000元二等奖3名 奖金:1000元三等奖 5名 奖金:500元纪念奖 若干名 赠送奖品会议论文范围包括所有与声学有关的研究论文及科技成果,欢迎广大声学工作者积极投稿,踊跃参加。征文截止日期:1999年6月15日录取通知发出时间:1999年7月20日会议时间:1999年10-11月会… 相似文献
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The crystal structure of the title compound(C17H12ClFO5,Mr=350.72) was determined by single-crystal X-ray diffraction.The crystal belongs to monoclinic,space group P21/c,with a=7.693(1),b=15.767(1),c=12.986(1),β=97.23(1)°,V=1562.6(2)3,Z=4,Dc= 1.491 g/cm3,λ(MoKα)=0.71073,F(000)=720,μ(MoKα)=0.280 mm-1,R=0.0563 and wR=0.1674.A total of 3592 unique reflections were collected,of which 2462 with Ⅰ2σ(Ⅰ) were observed.Five-membered lactone rings and hydroxyl-substituted phenyl rings are approximately coplanar with their dihedral angle of 4.1°.The dihedral angle between two different phenyl rings is 71.3°.To our interest,intramolecular O(1)-H(1)···O(4) hydrogen bonds could be found in each molecule.Intramolecular hydrogen bonds and intermolecular van der Waals force contribute to the stability of the structure. 相似文献
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The title compound of 4-(2-methylene-1-ethyl-3,3-dimethylindoline-2'-yl)-6,8-dibro-mo-1'-ethyl-3',3'-dimethylspiro[3,4-dihydro-2H-1-benzopyran-2,2'-indoline],C33H36Br2N2O,as a dicondensed spiropyran(DC) has been synthesized by indoline in ethanol with 3,5-dibromo-salicyaldehyde.The compound was characterized by elemental analysis and IR spectra.Meanwhile,the crystal of the compound was obtained and determined by X-ray single-crystal diffraction.Crystal data:monoclinic system,space group P21/n,a=12.9699(15),b=12.5196(13),c=19.327(2),β=106.493(3)°,Mr=636.46,V=3009.1(6) 3,Z=4,F(000)=1304,Dc=1.405 g/cm3,μ=2.722 mm-1,R=0.0554 and wR=0.1176 for 6892 independent reflections(Rint=0.0354) and 5699 observed reflections(Ⅰ 2σ(Ⅰ)). 相似文献
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The title compound (E)-4-tert-butyl-N-(2,4-dichlorobenzylidene)-5-(1,2,4-triazol-1-yl)-thiazol-2-amine was synthesized by the reaction of 4-tert-butyl-5-(1,2,4-triazol-1-yl)-thiazol-2-amine with 2,4-dichlorobenzaldehyde, and its crystal structure was determined by singlecrystal X-ray diffraction. The crystal belongs to the triclinic system, space group P1 with a = 7.9748(4), b = 10.1803(5), c = 11.4603(6), α = 102.882(1), β = 100.253(1), γ = 104.457(1)°, V = 850.95(7)3, Z = 2, F(000) = 392, C16H15Cl2N5S, Mr = 380.29, Dc = 1.484 g/cm3, S = 1.095, μ = 0.512 mm-1, the final R = 0.0301 and wR = 0.0965 for 3334 observed reflections (I 2σ(I)). The preliminary antitumor activity shows that for the title compound the IC50 of Hela is 0.175 μmol/mL and that of Bel7402 is 0.156 μmol/mL. 相似文献
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<正>The title compound,trans-bis(acesulfamato-O)tetraaquazinc(Ⅱ)(I,C_8H_(16)N_2O_(12)S_2Zn), crystallizes in the triclinic system,space group P_1~-with a=5.1638(5),b=8.5338(9),c=9.9583(9) (?),a=74.325(8),β=81.112(7),γ=75.800(8)°,V=407.77(7)(?)~3,Z=1,F(000)=236,R_(int)=0.085, T=296 K,the final R=0.029 and wR=0.078 for 1832 observed reflections with I2σ(I).The Zn~Ⅱcentre resides on a centre of symmetry and has a distorted octahedral geometry.The basal plane is defined by two carbonyl O atoms of two monodentate trans-oriented acesulfamato ligands and two trans-aqua ligands.The axial positions in the octahedron are occupied by two trans-aqua ligands. Intermolecular O-H…O hydrogen bonds produce R_2~2(8)and R_2~2(16)rings,which lead to two-dimensional polymeric chains. 相似文献
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