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C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 普通水所包含的分子通过氢键松散地结合成巨大的网络结构。难道在聚合水中这种网络结构会因某种原因而变得更加坚固吗?在本文中,普林斯顿大学的利兰·艾伦提出了一种聚合水的模型,在该模型中,连接着水分子的是一种新型的氢键,其中的每个氢原子都位于两个氧原子的中间,而不是像在正常水和冰中时那样非对称地排布。令人惊奇的是,目前已经知道这种对称的氢键是有可能存在的,只不过仅在高压下的冰中存在而已。最终证明聚合水本身并不需要任何解释,因为它仅仅是实验中的人为产物。 英文
最近,大家对杰里亚金[1]发布的可能存在一种新形式水的报道非常关注,不仅因为水的广泛存在,还因为人们几乎可以肯定这种新形式水必然需要一种新型的化学键。刘易斯[2]的点图是反映电子在分子... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 其中之一[5]是认为存在一对共振结构——由六个中性水分子排列成的六边形,再加上由三个(OH)–和三个(H3O)+交替排列组成的结构。中性的排列并不能反映水分子间键的性质。因为(H3O)+中氧原子所带的负电荷太小,而(OH)–中的则太大,所以这种共振形式存在的可能性很小。另一个模型[8]假定氧原子周围的对称型氢键和x、o的分布都与图1中的情况非常相似;但是没有强调氧原子上的负电荷。氧原子排列在准纤维锌矿结构(就像六方晶系的冰I)或准闪锌矿结构(就像立方晶系的冰I)中。这些结构的能量都比本文报道的结构能量高,因为存在起反作用的静电互斥项。利平科特等人[5]也构思出了属于这种类型的一个结构,但被推翻了,其中一部分原因在于由他的模型推导出的... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | human ova recovered by laparoscopy just before ovulation; preliminary observations have been given elsewhere2,3. 中文
Development beyond the pronuclear stage has proved difficult in several species, for example in mice. We have few human embryos for study, and have based our work on observations of animal embryos. Whitti... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | Ejaculated spermatozoa were supplied by the husband. The spermatozoa were washed twice by gentle centrifugation in the medium under test, and made up to a final concentration of between 8×105 and 2×106/ml. depending on the quality of the sample. The higher numbers were used with samples of poor quality containing many ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | The cumulus cells began to dissociate within 2–3 h of insemination, although corona cells remaining closely or loosely attached prevented the examination of some oocytes by low-power microscopy 15 h after insemination. The cells were left in place after attempts to remove them had led to damage of some oocytes. Criteri... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | Between 12 and 15 h after insemination, the oocytes were gradually transferred from the medium used for fertilization into various other media for cleavage. At least five embryos were cultured in each medium, except for medium 199. All media were adjusted to a pH of approximately 7.3. A total of thirty-eight embryos cl... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | Fig. 1. A 4-celled egg grown in Waymouth’s medium supplemented with calf serum. Development of this embryo had evidently been arrested.
中文
Ham’s F10 supplemented with 20 percent foetal calf serum was used at two osmotic pressures by adjusting the amount of water added; at 287 milliosmols/kg cleavage appeared abnormal... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | The amount of free follicular fluid added to the fertilization droplets must have been small, except for that in the viscous cumulus masses surrounding the oocyte. Various factors in follicular fluid are believed to be necessary for stimulating the spermatozoa and inducing changes in the acrosome16, and steroids presen... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | be made between different media. Results with defined media were inferior to those obtained from Ham’s F10 supplemented with foetal calf serum and with an osmotic pressure of around 300 osmols. Among various differences, F10 contains salts of heavy metals and more pyruvate than the other media. Development beyond the 8... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | We thank Mr. B. D. Bavister, Dr. D. G. Whittingham and Professor C. R. Austin for their help, Mr. C. Richardson for his assistance with photographs, and the Ford Foundation, the Manchester Regional Hospital Board and the Oldham and District Hospital Management Committee for financial support. We also thank Searle Scien... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | Weissman, G., in Lysosomes in Biology and Pathology (edit. by Dingle, J. T., and Fell, Honor B.) (North Holland, Amsterdam, 1969).
Channing, C. P., and Grieves, J. A., J. Endocrinol., 43, 391 (1969).
Bedford, J. M., J. Reprod. Fert., Suppl. 2, 35 (1967).
Abraham, G. E., O’Dell, W. D., Edwards, R. G., and Purdy, J. M., ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 受精小液滴的体积约为0.05毫升。 英文
一般认为:排卵前的卵母细胞会被黏性基质中的数层银色冠细胞和卵丘细胞包裹[1];而尚未进入排卵状态的卵母细胞则被封闭在较少层的冠细胞之中。处于闭锁状态的卵母细胞只有极少的细胞包裹或者完全没有细胞包裹。一开始,每个卵母细胞都被置于其自身的受精小液滴中,但是随后所有从同一患者中提取的卵母细胞都被聚集到了一起。那些包围在排卵前卵母细胞周围的大量细胞必然会使受精小液滴中的精子数受到一定程度的稀释。 英文
受精过程
以前的研究工作曾证明巴维斯特培养基能够维持受精过程[12-14],因此该培养基被广泛应用。在分析了人类卵泡液中的Na+含量和K+含量之后,我们对此培养基进行了稍许调整:将NaCl的浓度降低到... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 英文
通过调节水的含量,我们制备了具有两种不同渗透压的含20%胎牛血清的哈姆氏F10培养基:在渗透压为287毫渗摩/千克的培养基中,有2个胚胎的卵裂看起来不太正常;在渗透压为300毫渗摩/千克~305毫渗摩/千克的培养基中,有7个胚胎显示出完美的卵裂,接近或者超过了16细胞期。我们拍摄了另一个处于8细胞期的胚胎(图2),这个胚胎很可能还会继续卵裂。 英文
图2.一个在添加了牛血清的哈姆氏F10培养基中培养的8细胞期卵。这个胚胎是在卵裂期间被移出培养基的,要不然它也许还能继续发育。
英文
我们在培养过程中的多个时间点对胚胎进行了检查。结果发现,第一次卵裂发生在人工授精后38小时之内。有7个在惠廷厄姆培养基或哈姆氏F10培养基中培... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 英文
在这项研究中接受治疗的共有49位患者,我们从其中29位患者处获得了一个或多个胚胎。目前我们还无法评估正常发育胚胎的比率以及胚胎移植的成功率,尽管受试患者自身的胚胎移植条件应该是很有利的[1]。 英文
感谢巴维斯特先生、惠廷厄姆博士和奥斯汀教授给予我们的帮助,感谢理查森先生帮助我们拍摄照片,感谢福特基金会、曼彻斯特地区医院董事会和奥尔德姆地区综合医院管理委员会在经费方面的资助。还要感谢瑟尔科学服务部帮我们作了类固醇的检测实验。 英文
(吕静 翻译;王敏康 审稿)
Evidence that Polywater Is a Colloidal Silicate Sol
W. D. Bascom et al.
Editor’s No... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | Capillaries with internal diameters of 50 μm to 5 μm were drawn from acid (HNO3–H2SO4, 1:1) cleaned “Pyrex” and silica (GE 204) tubing. In some experiments the capillaries were loosely placed in “Pyrex” dishes over distilled water in a desiccator evacuated to about 40 mm Hg and held at 25°C±1°C. This is the procedure u... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | most of the condensate evaporated except for a residue with a gel-like appearance. In Fig. 1B the gel had formed before the liquid phase had fully evaporated. 中文
Fig. 1. Appearance of water condensate in a silica capillary immediately after removal from desiccator (A) and after most of condensate had evaporated (B). C... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | times the background level. The relative intensities for silicon and sodium were approximately equal. 中文
Fig. 5. Electron probe secondary electron emission (A) and silicon. X-ray emission (B) for a residue of condensate from silica. Cu substrate.
中文
Residues of dilute sodium silicate solutions also showed the annula... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | KHCO3. The bands at 1,650, 1,400 and 830 cm–1 are caused by bicarbonate and these same bands can be seen in the polywater spectra3,4. The broad band at 1,200–1,000 cm–1 is caused by silicate and the one between 3,700 cm–1 and 2,200 cm–1 is probably from residual water. 中文
Fig. 7. Infrared spectrum of residue of a sodi... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | In the case of condensate from silica capillaries, the electron probe gave clear evidence of sodium as well as silicon which implies contamination because the silica itself does not contain significant amounts of sodium. The principal source of this contamination was probably the glassware holding the capillaries; the ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | consistent with silicate solutions containing high proportions of metal cation10. 中文
The results reported here offer alternative explanations for the “polywater” phenomena. Samples of “anomalous water” prepared by the technique of Deryagin and co-workers have not yet been studied. They obtained condensate in very pure ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 英文
杰里亚金及其合作者曾提出证据证明:当正常的水蒸气在细小而洁净的玻璃或石英毛细管中凝结时,会生成一种新形式的水(即反常水)[1,2]。最近,利平科特等人[3]在这种毛细管中制备出了水的冷凝液并测试了它的红外光谱和拉曼光谱,据此他们断言该冷凝液中含有一种具有较高分子量的聚合态水,或称“聚合水”。应该对利平科特等人提出的“聚合水”与杰里亚金等人得到的“反常水”加以区分。俄罗斯的研究者们并没有声称反常水是一种高分子量的聚合水,而且他们在很多实验中都会格外小心地避免电解质对冷凝液的污染。本文中的研究结果说明:在利平科特等人所描述的实验中,盐类物质的污染是一个要考虑的重点问题。 英文
实验
内径为5 μm~50 μm的毛细管是由酸(HNO... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 英文
我们根据电子探针的结果可以得出以下结论:硅、钠和其他可能的阳离子即使不是这些冷凝液残余物的主要成分,也会是有很大影响的成分。在早期的研究[3]中可能出现过检测不到这些元素的情况,因为残余物太薄了。 英文
“聚合水”的红外光谱
如果硅酸盐是冷凝液的一部分,那么它就有可能为“聚合水”的红外光谱提供另外一种解释。硅酸盐溶液有较强的碱性,因而能够从大气中吸收CO2。“聚合水”光谱中的主要谱带位于1,600 cm–1和1,400 cm–1,与反对称和对称O–C–O伸缩振动的频率接近。为了验证硅酸盐就是冷凝液的一部分,我们对数滴被置于艾尔特兰II样品板上的碳酸氢盐–硅酸盐溶液残余物进行了红外光谱测定。图7中显示出了一个典型的结果,即来自含... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 英文
(王耀杨 翻译;李芝芬 审稿)
Human Blastocysts Grown in Culture
P. C. Steptoe et al.
Editor’s Note
Several months after they reported the successful production of eight- and sixteen-celled human embryos through in vitro fertilization (IVF), Patrick Steptoe, Robert Edwards and Jean Purdy report further advances. Improved tissue ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | A blastocoelic cavity appeared in four embryos. In two of them, the cavity was small and eccentric and the inner cell mass and trophoblast failed to become fully differentiated. Staining revealed only sixteen and twenty nuclei in the two embryos. The small number of cells indicated that division had become out of step ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | Fig. 1. Stained preparation of blastocyst 1. Many mitoses can be seen over the region of the inner cell mass (lower right) and a few elsewhere. The nuclei are even-sized.
中文
The second blastocyst (blastocyst 2) developed approximately 24 h after the other. It was cultured in Ham’s F 10 containing 25% human and 25% fo... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | We thank the Ford Foundation, the Oldham and District Hospitals Management Committee and the Manchester Regional Hospital Board for financial support, Mr. C. Richardson for photography and Professor C. R. Austin for encouragement. 中文
(229, 132-133; 1971)
P. C. Steptoe, R. G. Edwards and J. M. Purdy: Oldham General Hosp... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 英文
将囊胚在1%的柠檬酸钠中放置2 分钟,并用新鲜的醋酸–甲醇固定[5]。经醋酸–地衣红染色后,我们发现它含有112个细胞核和至少16个有丝分裂相(图1)。有几个分裂相在内细胞团区域重叠,因此无法对其作出判断。另一些虽然是相互分离的,但没有充分展开,因此我们只能猜测它们有可能是二倍体。 英文
图1.染色的囊胚1标本。在内细胞团区域(右下方)以及其他一些区域可以看到许多有丝分裂相。细胞核的大小是均一的。
英文
第二个囊胚(囊胚2)的发育时间比第一个囊胚晚大约24小时。它是在含25%人血清和25%胎牛血清的哈姆氏F 10培养基中培养出来的。培养159小时后囊胚腔出现。这个囊胚腔与我们在囊胚1膨胀阶段早期所见到的囊胚腔相同,但是穿... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | To be sure, in the nineteen sixties Kornberg and his collaborators isolated from Escherichia coli an enzyme which can polymerize DNA and, for example, replicate infectious bacteriophage DNA in vitro. And until last year this enzyme, DNA polymerase I, was the only known enzyme with this capability. Small wonder therefor... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | one of the six mutants isolated by De Lucia and Cairns. 中文
De Lucia and Cairns, when they began their mutant hunt, argued that if polymerase I is a repair enzyme it should be possible to select mutant E. coli with a defective repair mechanism, because of a defective polymerase I, but still capable of normal DNA replica... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | Fortunately as Kelley and Whitfield have now convincingly shown, pol 6, one of the half dozen mutants, turns out to be a temperature sensitive mutation. They purified polymerase I from this mutant and wild type E. coli and compared the properties in vitro of the two enzyme. The wild type enzyme has the same activity at... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 在那些致力于阐明DNA复制机制的分子生物学家们现在的研究清单上终于有了至少两个候选对象,他们目前更迫切要做的事情是:表征DNA聚合酶II的性质以及寻找其他种类的DNA聚合酶,而非极力设法让聚合酶I适应假想的DNA复制方案。现在,绝大多数分子生物学家都不会对以下陈述提出争议,即聚合酶I的主要功能是DNA修复,并且这很可能是它唯一的功能。如果还有摇摆不定者对此心存疑虑,相信等他们看了凯利和惠特菲尔德在本期《自然》杂志第33页上就德卢西亚和凯恩斯分离的6株突变体之一所发表的不得已的论述之后,就应该能作出最后的定论了。 英文
当德卢西亚和凯恩斯开始寻找突变体的时候,他们主张:如果聚合酶I是一种修复酶,那么就应当可以筛选出一种由有缺陷的聚合酶... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | not concede the matter until two years later. 中文
THE concept of an entirely new species of water (known variously as polywater, water II, or anomalous water) owes its publicity principally to Deryagin1 and his co-workers. Their conclusions have been based on their own experimental work on the physical properties of wat... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | If Deryagin’s chief contentions are correct, the problems facing the physical chemist are prodigious. He must interpret water II in terms of a completely new type of hydrogen bond which nevertheless can be easily formed during the condensation of slightly undersaturated vapours on to the appropriate surface. He must al... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | Our investigations have been in progress for the past 2.5 years and we have used all known methods of production as well as introducing many modes of our own. Fuller details of this work are being prepared for publication later. (We have too much material to be included here, but some of our results have been mentioned... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | residues arising from chemical cleaning of the apparatus (as in 2); (iii) back-streaming of rotary pump oil vapours even with the use of cold traps; (iv) resident apparatus gases such as carbon dioxide; (v) gaseous or organic impurities located at apparatus occlusions, dust particles and so on. 中文
Several groups have u... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | are recognized to contain organic impurities (see later) and Lippincott et al.4 admit to a small percentage of sodium and an unknown amount of carbon (see also other comments19,22 on the work of Lippincott et al.) 中文
For and against Polywater
It has been well established from the work of others and ourselves that the m... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | involved. First, implicit in Deryagin’s thinking is that, if a certain concentration of impure water in bulk does not deviate from ordinary water, this will be true for the same concentration of impure water in fine capillaries (note that he uses this type of assumption with his “quartz powder experiment”). Knowing the... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | production”, distillation and so on) affected by the surface migration and vapour transport of both water and impurities? We know from the experiments of others16,17 as well as ourselves that these factors cannot be neglected. One could raise many more objections specifically aimed at individual experiments. However, f... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | Some of the work supporting the case for anomalous water may at first seem impressive. Closer examination, however, shows that much of the published work is careless, inconclusive and often misleading, if not wildly conjectural. Our final conclusions are: first, the observed properties of so-called anomalous water are ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | Cherry, I., Barnes, P., and Fullman, J., Nature, 228, 590 (1970).
Hasted, J. B., Contemporary Phys., 12, 133 (1971).
Everett, D. H., Haynes, J. M., and McElroy, P. J., Nature, 224, 394 (1969).
Cherkin, A., Nature, 224, 1293 (1969).
Bascom, W. D., Brooks, E. J., and Worthington, B. N., Nature, 228, 1290 (1970).
Pethica,... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 他们必须应用全新的氢键理论来解释水II,这种氢键还得是当略微有点欠饱和的蒸气在适当表面上冷凝时能够顺利形成的。他们还必须解释,为什么稳定性不如水II的正常水会在自然界中占主导地位。所以我们对杰里亚金发现自己很难说服其他科学家一点也不感到奇怪,而一个名望不如他的人就更办不到了。不过,由于他不断地重复自己的观点,使得西方世界中(尤其是在英国和美国)的很多研究小组继续跟进他的工作。这些研究小组所得到的结果既是对他论点的支持也是对他论点的反驳。此外,还有几位理论工作者(例如,参考文献3~9)积极致力于为解释反常性质所需的新键型找到一种适当的量子力学模型;无需赘言,其中的某些模型在很大程度上是基于猜测[10]。 英文
大多数反对水II概念的证... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 事实上已经证明:(i)由含有各种盐类、泵油、硅、水溶胶以及诸如钠和硼之类的添加剂的溶液可以得到反常的相分离和密度–温度曲线,在正常水挥发后会留下它们特有的残余物(参考文献12、16、18和我们自己的研究);(ii)已发表的聚合水的红外光谱与多种化学物质溶液的红外光谱[16-18,20-23]非常相似,其中包括含羧基化合物、碳酸氢盐、硫酸盐、四硼酸钠、硝酸钠和硝酸钾,尤其是还有硝酸和人类的汗水。几乎没有什么疑问的是,反常水的所有已知性质都会在选择适当添加剂的情况下再现。显然,不同实验、甚至不同样品中杂质的具体组成必定会随着所报道的反常水性质的不同而有所不同。值得注意的是,不同研究者使用的浓度也不尽相同;有些人用的是完全挥发之前的极稀的... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 英文
感谢克兰皮特博士利用先进质谱技术协助我们进行了研究,并且要感谢富尔默研究院所作的电子探针显微分析。还要感谢贝尔纳、卡莱尔、哈斯特德、艾夫斯等几位教授和拜沃特博士、西尔博士以及赖姆尔小姐和富尔曼先生对我们的帮助。 英文
(王耀杨 翻译;李芝芬 审稿)
Convection Plumes in the Lower Mantle
W. J. Morgan
Editor’s Note
The idea that plumes of hot material well up within the Earth’s mantle to create surface “hotspots” was postulated by John Tuz... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | Fig. 1. The arrows show the direction and speed of the plates over the mantle; the heavier arrows show the plate motion at hotspots. This synthesis was based on relative plate motion data (fault strikes and spreading rates) and predicts the directions of the aseismic ridges/island chains emanating from the hotspots.
... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | triple junctions, but there is considerable displacement between the “pipes to the deep mantle” and the lines of weakness in the lithosphere which enable the plates to move apart.) Also, a large isolated hotspot such as Hawaii can exist without splitting a plate in two. I believe it is possible to construct a simple dy... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | My claim that the hotspots provide the driving force for plate motions is based on the following observations to be discussed below. (1) Almost all of the hotspots are near rise crests and there is a hotspot near each of the ridge triple junctions, agreeing with the notion that asthenosphere currents are pushing the pl... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | this pull as the principal tectonic stress. This leaves sub-lithospheric currents in the mantle and the question now is: are these currents great rolls (mirrors of the rise and trench systems), or are they localized upwellings (that is, hotspots)? 中文
A recent world gravity map10 computed for spherical harmonics up to o... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | versus oceanic simplicity, but the model presented here predicts that most hotspots will be near a spreading rise. 中文
I thank Kenneth Deffeyes and Fred Vine for their contributions to the ideas in this letter. This work was partially supported by the US National Science Foundation and the Office of Naval Research. 中文
(... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 每个上涌点将具有独特的岩石学特征与运动学特征,但我假定不存在与之对应的单一下降点,回流是均匀地分布于整个地幔之中的。埃尔萨瑟私下里曾声明:根据线性黏性方程,极不稳定的流体会形成雷暴云砧式流而非卷流或对流环模式。在软流圈中,从各上涌点沿半径向四周流出的流体将对岩石圈板块的底部产生压力,该压力与由洋脊、断层以及海沟处的板块间相互作用产生的压力一起决定了各个板块的运动方向。 英文
显然,板块间的相互作用在决定板块上的净作用力方面非常重要,因为现今的洋脊、断层及海沟都有维持自身连续性的趋势。板块似乎非常坚硬并可以抵抗重大的变化,因为通常情况下隆起脊不会逐渐消失而是迁移到新的位置,而深处的上涌点也并不一定与脊峰线重合。(例如,加拉帕戈斯群岛和... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 英文
在大西洋周边的陆地上存在着热点活动的陆相证据:巴塔哥尼亚地区的侏罗纪火山岩(由现今的布韦岛地幔柱形成)、非洲西南部的环形岩墙杂岩和巴拉那盆地中的溢流玄武岩(特里斯坦-达库尼亚地幔柱)、新罕布什尔州的白山岩浆系列(与形成新英格兰海山链的热点相同(亚速尔地幔柱?))、斯卡尔噶德和苏格兰第三纪火山区(冰岛地幔柱)等等。我认为,这一系列热点共同引起了流体在软流圈中的流动,进而导致大陆分离形成了大西洋。同样,德干玄武岩(留尼汪地幔柱)是印度洋裂谷即将形成的征兆。我们应该去寻找类似的陆地活动以解释在那里发现的裂谷构造,尤其是在东非和美国西部地区(斯内克河玄武岩?)。从图1来看陆地上的热点很少,也许这是一种因陆地相对复杂和海洋相对简单而导致... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | “wave field” theory of the Crab Nebula leads to some distinctive predictions, especially regarding the polarization of the continuum. It may therefore be possible to test its validity and thus, indirectly, to infer something about the energetic link between the nebula and the pulsar. 中文
The rate of emission by an isotr... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | Some of the rotational energy lost by an “oblique rotator” would accelerate relativistic particles in the vicinity of the speed of light cylinder1, but for our considerations to be relevant it is essential that a substantial fraction (~10% at the very least) should escape into the nebula as 30 Hz radiation. It is inter... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | a circle. All particles exposed to the wave must therefore be relativistic with . Because the orbits of particles with γ≫f are basically straight lines, the wave field is ineffective for confining particles. But even a very weak magnetic field, which is negligible as regards the emission mechanism, could confine the pa... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | It would be agreeable if the “wave field” theory led to a clear-cut prediction of the surface brightness distribution over the Crab Nebula, but unfortunately this is not the case. The r−1 dependence of Heq means that a particle radiates more efficiently near the centre, but there would not necessarily be an enhanced su... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | angles π/2±O(f−1) to v. This radiation would be circularly polarized in opposite senses on the two sides of the orbital plane. In the transformation from the guiding centre frame to the source frame, however, the factor (1−v/c cos θ) in the Doppler formula favours the emission from the forward hemisphere by a factor ~(... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | linearly polarized parallel to the rotation axis. The direction of linear polarization will be similar at other latitudes (and even along lines of sight intercepting the rotation axis there will be a linearly polarized contribution). Both the optical and the radio observations show fairly uniform linear polarization in... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | the wave. Also, when μ differs from unity the low frequency wave will be refracted, and can no longer be assumed to propagate radially outward from the pulsar.) 中文
In conclusion, the simple “wave field” model can account naturally for the high linear polarization in the Crab Nebula, and for the required highly efficien... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | Ostriker, J. P., and Gunn, J. E., Astrophys. J., 157, 1395 (1969).
Hoyle, F., Narlikar, J. V., and Wheeler, J. A., Nature, 203, 914 (1964).
Wheeler, J. A., Ann. Rev. Astron. Astrophys., 4, 393 (1966).
Pacini, F., Nature, 216, 567 (1967).
Rees, M. J., IAU Symposium No. 46, “The Crab Nebula” (edit. by Davies, R. D., and ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | ε是星云边界处的有效反射率,而因子是允许有反射的。对蟹状星云来说,括号里的所有项都将为~1。因此波的能量密度就会与能量和动力学所允许的最弱磁场(~10−4 G)的能量密度相当。定义一个“等价电子回旋频率”Ω/2π≃ 3×106HeqHz也是很有用的,因为参数f = Ω/ω(其中ω为波的频率)决定了波中电子轨道的性质以及这些粒子发出的辐射。 英文
对于整个蟹状星云,我们预言(取ω/2π≃30 Hz)。在这种情况下,洛伦兹因子为γ的相对论性粒子会在频率~γ2Ω下发射,而不会在频率~γ2ω下发射;前者与同步辐射时的情形相同,后者则相当于标准的逆康普顿辐射[5-7]。本文将讨论这种“同步–康普顿”辐射的观测特征,尤其是它的偏振。不过,就现在... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 在这个参考系中,电子是在一个几乎垂直于其平均速度v的平面内作圆轨道运动(除非当粒子近似沿着波的传播方向运动时)的,洛伦兹因子为f。这种运动将产生集中在一个与v成π/2±O(f−1)角范围内的“扇形区域”中的同步辐射型辐射。这个辐射在轨道面的两边应该是方向相反的圆偏振。然而,在从导向中心参考系到源参考系的变换中,多普勒公式里的(1−v/c cos θ)因子使得来自前面半球的辐射多出一个~(1+f−1)/(1−f −1)因子,这就导致了一个净的~f−1的偏振。采用罗伯茨和科梅萨罗夫[10]的方法对上述过程进行更为精确的计算,得到的结果是~0.6 f−1。因此,各种能量电子的同步–康普顿辐射可能会有量级为f−1的圆偏振。由此可知,来自于在... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | Configuration of Amino-Acids in Carbonaceous Chondrites and a Pre-Cambrian Chert
J. Oró et al.
Editor’s Note
Chemist John Oró and his colleagues in Texas reported finding amino acids in carbon-rich meteorites (see next paper), raising questions about the role of meteorites as a source of raw ingredients for the origin ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | our laboratory on tar covered bones from the Rancho La Brea, Los Angeles, show significant racemization after 12,000 yr. Thus, an L configuration of the amino-acids in meteorites would be evidence for contamination, whereas the presence of racemates would argue for chemical synthesis or for very old biogenic amino-acid... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | peaks is changed on co-injection of the DL standard, as expected. The small peak in the proline region does not coincide with the L-isomer (see co-injection), nor with the D-isomer (relative retention time).
中文
Fig. 2. Mokoia meteorite. Chromatogram of the N-TFA–isopropyl esters of the amino-acids from acid hydrolys... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | † Below limits of detection. A small amount of D-serine might be present in the L-leucine, since the peaks of the N-TFA–isopropyl esters of these two compounds overlap. For this same reason no data are given for the enantiomeric composition of serine.
‡ D-Alloisoleucine was added to this meteorite as an internal standa... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | during the entry of the meteorite through the atmosphere, or during the acid hydrolysis step, and on the configuration and inversion of amino-acids in soils. The presence of traces of β-alanine in Murray (Fig. 3) could also be an indication of abiogenesis, but it is known that this amino-acid can be formed by bacterial... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | We thank Dr. A. Cavaille, Dr. E. P. Henderson, Dr. C. B. Moore, Professor J. Orcel, and Dr. K. A. Kvenvolden for their help in obtaining samples. We also thank Mr. J. M. Gibert and Mr. J. C. Raia for assistance. This work was supported in part by grants from NASA. 中文
(230, 107-108; 1971)
J. Oró, S. Nakaparksin, H. Lich... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | Gil-Av, E., Charles-Sigler, R., Fischer, D., and Nurok, D., J. Gas Chromatog., 4, 51 (1966).
Pollock, G. E., and Oyama, V. I., J. Gas Chromatog., 4, 126 (1966).
Kvenvolden, K., Lawless, J., Pering, K., Peterson, E., Flores, J., Ponnamperuma, C., Kaplan, I. R., and Moore, C., Nature, 228, 923 (1970).
碳质球粒陨石与一块前寒武纪燧石中的氨... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 英文
上述结果表明碳质球粒陨石中的氨基酸可能有多重来源。奥盖尔和莫科亚样品的数据显示(图1和图2;表1):这些陨星样品中的结合氨基酸几乎全部是L构型,只有D–丙氨酸例外,它在两个样品中的含量分别为22.5%和6.5%。尽管基于对陨星样品用有机溶剂和水进行的彻底清洗有可能可以把这个现象解释为L–氨基酸具有地外起源,但我们相信大部分结合氨基酸是源自地球上微生物造成的污染。一些D–丙氨酸的存在与这一结论并不矛盾,因为这种特殊的D型异构体也存在于细菌的细胞壁和其他微生物中。在每克莫科亚样品中至少观测到了1,800个活细菌[12],而死去的微生物估计还会比这高出30倍[13]。 英文
表1.碳质球粒陨石和一份土壤样品的水解产物中氨基酸D型对... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 英文
(王耀杨 翻译;周江 审稿)
Amino-Acids, Aliphatic and Aromatic Hydrocarbons in the Murchison Meteorite
J. Oró et al.
Editor’s Note
From where did the earliest life on Earth get its raw ingredients? The discovery of complex carbon-based (organic) molecules in meteorites in the 1960s by John Oró at the University of Houston and ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | protein amino-acids such as alanine, valine and proline10. 中文
The presence of D and L enantiomers of protein amino-acids, and aspartic acid, has been observed before in the fraction containing the bound amino-acids of the Murray meteorite11. The predominance of the L configuration observed in this case, and a compariso... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | volume). The eluate was evaporated as described and the residual amino-acids were esterified with 3 M HCl–isopropanol at 100°C for 30 min and then converted into N-trifluoroacetyl–amino-acid–isopropyl esters13,14. Aliquots (in CHCl3) of these derivatives were analysed by combined gas chromatography and mass spectrometr... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | of either L or D configuration; (c) formation by synthetic or decomposition reactions during the entry of the meteorite through the terrestrial atmosphere, and (d) chemical synthesis from amino-acid precursors during the hydrolysis of the water extracts. Although (d) cannot yet be ruled out, the first mode of synthesis... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | Fig. 1B shows a representative gas chromatogram of the pentane fraction. The aliphatic hydrocarbons observed range from C10 to relatively high molecular weight components. The most abundant series corresponds to the branched saturated alkanes. They include predominantly monomethylated and dimethylated isomers. Intense ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | Overall, the Murchison meteorite contains substantial amounts of extractable organic compounds, which give distribution patterns significantly different and much more complex than those observed previously, indicating abiotic synthesis, extensive diagenesis and related chemical processes, or both. This carbonaceous cho... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | Gelpi, E., Koenig, W. A., Gibert, J., and Oró, J., J. Chromatog. Sci., 7, 604 (1969).
Nakaparksin, S., Birrell, P., Gil-Av, E., and Oró, J., J. Chromatog. Sci., 8, 177 (1970).
Oró, J., Updegrove, W. S., Gibert, J., McReynolds, J., Gil-Av, E., Ibanez, J., Zlatkis, A., Flory, D. A., Levy, R. L., and Wolf, C. J., Geochim.... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 英文
图1A显示的是一张具有代表性的气相色谱图:将1微升N–三氟乙酰基–异丙酯注入LKB 9000气相色谱–质谱联用仪的内径为150米×0.5毫米、涂有3%SF–96固定液的毛细管气相色谱柱中。这种有效塔板数为180,000的色谱柱也可用于对烃类物质的分析。前期通过质谱得到的结果证明了甘氨酸、丙氨酸、2–甲基丙氨酸、氨基丁酸、缬氨酸、谷氨酸、脯氨酸以及一些亮氨酸的存在。甘氨酸是所观测到的主要氨基酸(5.3微克/克),而其他氨基酸只有数量级为0.1微克/克的量或者略多些(丙氨酸为3.1微克/克)。气相色谱分析表明试样中存在着很多组分,因此仍有相当数量的其他氨基酸(可能还有胺类)需要鉴别。但有超过一半的主峰所代表的物质已经得到了确定,其... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 英文
(王耀杨 翻译;周江 审稿)
Ball Lightning as an Optical Illusion
E. Argyle
Editor’s Note
For centuries, eyewitness accounts have attested to an elusive atmospheric phenomenon known as ball lightning: the creation during thunder storms of spherical balls of luminous energy which float through the air, persist for several second... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | the luminous intensity within the sphere is high enough to create a positive afterimage in the eye of an observer. In his comprehensive survey of reports on ball lightning Rayle12 made the interesting discovery that “the number of persons reporting ball lightning observations is 44% of the number reporting observation ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | Being a cone effect, the positive afterimage will usually be formed near the centre of the retina, and the observer, wishing to examine the supposed object, will attempt the impossible task of centring it exactly. The result is a linear drift of the projected positive afterimage across the observer’s visual background,... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | The psychological principle for imagining odour is the same as for sound but fewer individuals have strong odour expectations and in only a few cases are odours reported. An appropriate odour would be one the observer associates with electrical apparatus, if he has some familiarity with it; or with deeper metaphysical ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | record. 中文
Final resolution of the question of the nature of ball lightning will no doubt depend more on the outcome of further experimentation than on the collection of more observer reports. Fortunately, the question of the reality of ball lightning is amenable to laboratory investigation. I have found it easy to sim... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | Folinsbee, R. E., Douglas, J. A. V., and Maxwell, J. A., Geochim. Cosmochim. Acta, 31, 1625 (1967).
Goodlet, B. L., J. Inst. Elec. Eng., 81, 1 (1937).
球状闪电是一种视错觉
阿盖尔
编者按
几个世纪以来的目击证据已证明有一种被称为球状闪电的神秘大气现象是存在的:在遭遇雷暴天气时会形成一些漂浮于空气中的具有光能的球状物,短暂停留几秒钟然后突然消失,它们的大小从一块小石头尺寸到几英尺直径不等。因为很难通过科学方式来研究这一现象,所以人们对此一直争论不休。1970年报道的几桩事件使爱德华·... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 奇怪的是,报道称人们在室内看到的闪电球在消失时通常是很猛烈的,但是几乎不会造成破坏。 英文
根据心理学原理,在听觉和嗅觉上的幻觉是一样的,但是很少有人对气味有强烈的预期,因此关于球状闪电有气味的报道只有为数不多的几个例子。一种适当的气味可以让观察者联想到他所熟悉的某种电气设备;或者更玄妙地和危险、神秘联系起来。比如,如果他的联想朝超自然的方向延伸,他会联想到地狱里的磨难。以上谈到的是对球状闪电气味的报道[18]。 英文
在白天日光非常强烈的情况下,正余像是十分罕见的。但是,当光线暗淡的时候,比如恰好遇到雷暴天气,尤其是在观察者处于室内的情况下,任何一个亮度类似于磨砂灯泡的光源都很容易使正余像得以形成。因为闪电主要是发生在户外的现象,... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | SINCE Landsteiner described the ABO blood group system1, it has become increasingly obvious that human individuality is demonstrable at the molecular level. It seems probable that almost every protein, structural or enzymatic, can be made to reveal some degree of variability in human populations. The application of sta... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | The peptidases illustrate well the sort of information that can be obtained by the application of starch gel electrophoresis in association with a specific staining method. The occurrence of these enzymes in human tissues has been established for some time4; they catalyse the hydrolysis of the peptide bonds of small pe... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | Biochemical evidence suggests that the six peptidases are distinct proteins, each with a characteristic primary structure and a characteristic specificity. It would be expected therefore that the primary structure of each peptidase would be coded for by a separate gene locus, so that a structural variant occurring in o... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | allele is apparently expressed in the heterozygote. 中文
This type of study also makes possible inferences about the molecular structure of an enzyme. The electrophoretic pattern of the presumed heterozygote Pep A2–1 consists of three main zones of activity, a zone with a mobility equivalent to each of the presumed homoz... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | tissue extract, for example placenta, the pattern is symmetrical and the three main bands have activity roughly in the ratio of 1:2:1. It seems likely that the stability difference is revealed in the red blood cell because of the relatively long half life of this type of cell, and presumably protein synthesis has cease... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | It seems probable that the genetic code is common to most species14. If so, it is possible to postulate the particular amino-acid substitution that has occurred in the subunit coded for by the Pep A5 allele. The only amino-acid which has a reactive sulphydryl group which is found in proteins is cysteine. This amino-aci... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | the same chromosome or situated on different chromosomes. 中文
Another interesting group of isozymes which illustrates this type of variation in human populations is phosphoglucomutase (PGM). These enzymes are very specific phosphotransferases which catalyse the reaction
Using glucose-1-phosphate as the substrate it is ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | Electrophoresis of red cell lysates also reveals a second series of isozymes migrating further towards the anode which do not show any variation associated with that which occurs in the slower moving group (PGM1). It was suggested that these faster moving isozymes (PGM2) were controlled by a second gene locus, and late... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | The implications of this type of variation in the primary structure of proteins in human populations are quite wide ranging, both for theoretical human biology and in the practical aspects of the study of the human organism. It is possible that common variants of a particular enzyme provide a pool of variability within... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | effect until the individual is exposed to a toxic compound such as a drug or a particular type of food, as is seen with two different variants of glucose-6-phosphate dehydrogenase26,27. In one case, treatment with the antimalarial drug, primaquine, induces a haemolytic crisis and, in the other, ingestion of the fava be... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | On the other hand, the accumulation of a high concentration of D may in itself be toxic, and this situation is found with some inborn errors of metabolism, such as galactosaemia28,29, although in these cases the level of activity of the affected enzyme is usually very low indeed, and perhaps beyond the limits of detect... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | Hopkinson, D. A., and Sinha, K. P., Ann. Human Genet., 33, 139 (1969).
Crick, F. H. C., Proc. Roy. Soc., B, 167, 331 (1967).
Blake, N. M., Kirk, R. L., Lewis, W. H. P., and Harris, H., Ann. Human Genet., 33, 301 (1969).
Hopkinson, D. A., and Harris, H., Ann. Human Genet., 30, 167 (1966).
Detter, J. C., Ways, P. O., Gib... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 英文
自兰德施泰纳描述了ABO血型分类系统以来[1],日益显而易见的是,人类的个体差异可以在分子水平上得到验证。似乎可能的是:几乎每一种蛋白质,无论是结构性蛋白还是酶蛋白,都能够用于揭示人群的一定程度的变异性。在过去的十年中,通过利用淀粉凝胶电泳法[2],人们相当有成效地揭示出了人体中特定酶分子的变异性。正是通过使用这种方法,人们才发现:在任意一个主要的人群中,大概每三种酶中就会有一种存在常见的变异体[3]。考虑到淀粉凝胶电泳法只能揭示出酶蛋白所带电荷差异或大小差异这一事实,上述发现就更加值得我们思考。非常可能的情形是,利用这种技术检测出的结构差异是由一个特定的氨基酸被另一个带电不同的氨基酸所替代而引起的,而在所有可能的氨基酸替代中... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 如果用α1代表由肽酶编码基因A1编码的亚基,用α2代表由肽酶编码基因A2编码的亚基,那么如果在杂合子个体中这两个等位基因都被表达,并且它们对应的亚基随机组合,则有可能会出现以下三种结构:α1α1、α1α2和α2α2。此外,如果这两个亚基的合成速率相同并且活性和稳定性也相同的话,那么就可以推出这三条电泳带的活性之比约为1∶2∶1,而实验结果似乎正是如此。 英文
与这种特定肽酶有关的另一个有意思的现象是一系列罕见表型的发生(图2)。所有这些表型都非常罕见,它们在迄今为止研究过的大多数人群中的出现频率等于或低于1/1,000。家族研究结果表明,这些表型的出现是因为杂合子个体中的等位基因中的一个是如下等位基因:肽酶编码基因A3、肽酶编码基因... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 通过在pH值7.4条件下电泳后再使用这种方法染色,人们揭示出了人群中磷酸葡萄糖变位酶的多态性[20]。三种表型PGM1、PGM2–1和PGM2的电泳图谱示于图3。这种多态性发生于大多数人群中,尽管基因频率有所不同。 英文
图3.对三种常见的PGM类型个体样品进行电泳检测后拍摄的电泳图谱照片和所作的图解。(来自参考文献20)
英文
大量家族研究的结果表明:这些不同的电泳类型是由一对常染色体等位基因的出现产生的。具有PGM1或者PGM2表型的个体从表观上看是其中一个等位基因的纯合子。其电泳图谱(图3)显示为两条带(译者注:根据下文的描述,这里所说的两条带应该指的是靠近阴极的两条带),这两条带在PGM2中比在PGM1中更靠近阳极。P... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | 如果我们考查一个如下图所示的假想的三酶系统,而且如果在正常情况下两种酶α和β的浓度正常,并有25%的A转变成了D,那么,如果α被更不稳定或者催化活性更弱的α’所替代的话,则A向B的转化率就会降低,更多的A就会被代谢转变成D。 英文
在大多数情况下,这样一种情形本身也许不会对个体产生任何可被测量的影响。但如果个体面对的是一种B或者C的浓度处于导致代谢危机的临界值的情形,那么效应就很可能是相当剧烈的,就像伯氨喹敏感性导致的结果那样[26,27]。 英文
另一方面,高浓度D的积聚本身也许就是有毒性的,这种情况出现在某些先天性代谢障碍中,比如半乳糖血症[28,29],不过在这些例子中所影响的酶的活性水平实际上总是很低,而且可能已经超出了检... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0307. 《自然》百年科学经典(英汉对照版)(第五卷)(1966-1972).epub | .epub | 16,876,645 | 2025-09-26T19:07:54.356078 | organisms. This is accumulation of genetic differences between geographically separated (allopatric) populations or races, followed by a gradual emergence of reproductive isolation between them4,5. Species formation through genetic divergence and its fixation by reproductive isolating mechanisms is a slow process, gene... | 400套付费套装书 |
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