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C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Further work on the ΦΧ sequence has been done using chiefly the plus and minus method primed with restriction fragments. Figure 2 shows the various restriction enzymes used and the fragment maps for each (refs 25-30 and C.A.H., submitted for publication, and N.L.B., C.A.H. and M.S., submitted for publication). 中文
Fig.... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | As template we have used both the viral (plus) and complementary (minus) strands of ΦΧ. Usually it is possible to determine a sequence with a single primer starting at about 15-100 nucleotides from the appropriate restriction enzyme site. In a particularly good experiment the sequence can be read out to 150-200 nucleot... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Sinsheimer et al.34,35 and Axelrod36 have determined the sequences of the 5′ end of three ΦX in vitro mRNA species and have located them on the restriction map. These sequences have been identified on the DNA sequence and one of them (AAATCTTGG) is found only at position 3,954 at which an in vivo unstable mRNA start ha... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | overlapping. 中文
Fig. 3. Potential secondary structure at the A mRNA start.
中文
The A Protein
Where the amino acid sequence is available there is no problem in relating the DNA sequence to its coding properties, but it is more difficult to do so in the absence of such data, as is the case for the A protein. One way of... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | * These figures refer to the last five codons of the previous line and the first five of the next line.
中文
A different approach to identifying the initiation site and reading phase in a coding sequence is by looking for a characteristic “initiation sequence”. Shine and Dalgarno have shown that a common feature of ribo... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | of about 35,000, is believed to result from an internal translational start in the A gene, in the same reading phase45. From consideration of possible ribosome binding sequences42,43 the ATG in position 4,657 seems to be the most likely initiation site for the A* protein. 中文
The Origin of Replication
The origin of ΦΧ v... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | The second of the mRNA 5′ sequences (AUCGC)34 has been mapped in restriction fragment R8 (Fig. 2), which starts about 300 nucleotides on from the proposed A* initiation. The sequence ATCGC is found at positions 4,832 and 4,888 in Fig. 1. The only way we can choose between them at the moment is that the second is preced... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | varied with gel concentration and cross linker. Such anomalous behaviour suggests that there may be, for instance, carbohydrate attached to the B protein. 中文
The C Protein
The next known gene product, protein C, maps between genes B and D. Examination of the DNA sequence in this region indicates that the most probable ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | sequence of the small basic protein (37 amino acids) of the virion determined by D. Freymeyer, P. R. Shank, T. Vanaman, C.A.H. and M. H. Edgell (personal communication). Benbow et al.2,3 suggested that the mutation am6 was located in a gene J, coding for the small protein of the virion, and mapping immediately before g... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | The termination signal for the F protein (position 2,276) is followed by an unusually long untranslated sequence of 111 nucleotides until the G protein initiation codon31. This region contains a looped structure which was postulated to have some functional role, as yet unknown, in the single-stranded DNA or the mRNA. 中... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | The most striking feature of the ΦX DNA sequence is the way in which the various functions of the genome are compressed within the 5,375 nucleotides. Since the identification of ΦX gene products2,4 it has been clear that proteins of the accepted molecular weights could not be separately coded on the available length of... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | The sequences preceding known mRNA starts34-36 are shown in Table 3. Other studies on promoter sequences38 have suggested certain features that they may have in common. Although some of these features are present in the sequences preceding the ΦX transcription initiations others are not, and at present it is difficult ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | The totals are derived from sequences in Fig. 1 which are fully confirmed, that is, 377 codons in gene A, 120 in gene B, 152 in gene D, 91 in gene E, 38 in gene J, 344 in gene F, 175 in gene G and 49 in gene H. Out of a total of 1,346 codons 42.9% terminate in T. The percentages in the different genes are: A, 37.1 (non... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Hall, J. B. & Sinsheimer, R. L. J. Molec. Biol. 6, 115-127 (1963).
Ling, V. Proc. Natl. Acad. Sci. U.S.A. 69, 742-746 (1972).
Harbers, B., Delaney, A. D., Harbers, K. & Spencer, J. H. Biochemistry 15, 407-414 (1976).
Burton, K. & Petersen, G. B. Biochem. J. 75, 17-27 (1960).
Chadwell, H. A. Thesis, University of Cambri... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Air, G. M., Sanger, F. & Coulson, A. R. J. Molec. Biol. 108, 519-533 (1976).
Barrell, B. G., Air, G. M. & Hutchison, C. A. III Nature 264, 34-41 (1976).
Smith, L. H. & Sinsheimer, R. L. J. Molec. Biol. 103, 699-735 (1976).
Grohmann, K., Smith, L. H. & Sinsheimer, R. L. Biochemistry 14, 1951-1955 (1975).
Axelrod, N. J. ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | van Mansfeld, A. D. M., Vereijken, J. M. & Jansz, H. S. Nucl. Acids Res. 3, 2827-2843 (1976).
噬菌体ΦX174的DNA核苷酸序列
桑格等
编者按
至1977年,英国生物化学家弗雷德里克·桑格已经开发出了用于DNA测序的“双脱氧”法。本文中,他应用这种方法对ΦX174噬菌体的基因组进行了测序,使其成为第一个被完全测序的DNA基因组。这个单链环状基因组只包含5,000多个核苷酸。紧接着桑格的研究小组对人类线粒体DNA进行了测序,还开发了全基因组鸟枪法破译了分子生物学研究中一个重要病毒——λ噬菌体的基因组。桑格的工作为所有的基因组测序项目奠定了... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 赛达特[21]等将他们的研究拓展到更长的核酸内切酶IV酶切片段,他们的研究结果与DNA片段的转录[20]、F蛋白的氨基酸序列[22]以及加减测序法的结果一起,使得在F基因中[23]推导出一段281个核苷酸的序列(1,016~1,269区域,图1)成为可能。进而根据HindII酶切片段10的转录和G基因的氨基酸序列数据,以及利用HindII片段2和10作为引物的加减法测序,又推断出G基因N末端的195个核苷酸的序列(2,387~2,582区域,图1)(参考文献24)。 英文
“加减法”测序
我们用限制性酶切片段作为引物,首先主要使用加减法测序对ΦX序列进行了进一步的研究。图2显示了所用的各种限制性内切酶和每一片段的图谱(参考文献25~... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 然而最近的研究(罗森堡,未发表的结果及参考文献41)表明终止的发生可能需要在终止位点前存在一个碱基配对的环结构。在DNA序列中这样一个环可能出现在T6A序列的前面,但在从3,954处起始的mRNA中并没有形成这个环(图3)。因此预计由更靠前的一个启动子启动并延伸通过H基因的mRNA可能终止于此,而新起始于3,954位点的mRNA并不在此终止。这可能是噬菌体节约使用DNA的一种方式——使两个mRNA的末端重叠。 英文
图3. A基因mRNA起点可能的二级结构
英文
A蛋白
如果已知氨基酸序列就很容易推断出DNA序列的编码特性,但是像蛋白A这样缺少这些数据时这样做就很困难。鉴别DNA阅读框的一个方法是依据无义密码子的分布。对于一段... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 其他的用以下公式得出
英文
B启动子
第二个mRNA 5′序列(AUCGC)[34]绘制在限制性片段R8中(图2),它起始于之前所提及的A*起始位点后约300个核苷酸处。序列ATCGC在图1中的4,832位点和4,888位点被发现过。目前在它们之间选择的唯一方法是第二种序列位于序列TACAGTA(4,877位点)之后,与其他可能的mRNA起点之前的序列相比,序列TACAGTA与已知启动子中发现的序列更为相似[38]。不管采用这些序列中的哪一个,在下一个推测的起始密码子(基因B)之前mRNA都有一段长“引导”序列(232个或176个核苷酸)。 英文
B蛋白
通过对ΦX mRNA[49]核糖体结合位点的核糖核酸酶T1消化产物的研究,... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 这个基因中有些区域的DNA序列尚未完全完成,但其编码的蛋白长度大约为424个氨基酸,分子量约为46,300。 英文
G蛋白区域
F蛋白的终止信号(2,276位点)之后存在一段长达111个核苷酸的非翻译序列,直到G蛋白起始密码子[31]。这个区域包含一个环状结构,推测其在单链DNA或mRNA中有一些未知功能。 英文
G蛋白起始位点2,387后是一段425个核苷酸的序列,直到终止位点2,912,产生一个分子量为19,053的刺突蛋白。这个基因的核苷酸和氨基酸产物的序列是已知的[24,32]。 英文
H蛋白
H蛋白的起始密码子(位点2,923)最初是在3个阅读框之间T核苷酸分布的基础上鉴定出来的,随后通过氨基酸序列分析得到确认。关于H蛋白... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 共1,346个密码子,其中有42.9%的末位为碱基T。在不同基因中的百分比为:A,37.1(非重叠区域47.1;重叠区域15.8);B,34.2;D,42.1;E,14.3;J,47.4;F,52.0;G,54.3;H,49.0。所有例子中都包含起始密码子ATG。
英文
我们感谢麦卡勒姆和施塔登进行的计算机数据存储和序列分析。 英文
附加说明:西姆斯和德雷斯勒(个人交流)已经独立确定了263~375区域和4,801~4,940区域的序列。他们的结果与图1给出的一致。他们也鉴定了“B” mRNA起始于位点4,888处。 英文
(郑建全 李梅 翻译;曾长青 审稿)
Radio Sources with Superluminal Ve... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | The observations have all been obtained with very-long-baseline interferometry (VLBI) systems using two to five radio telescopes, spaced over thousands of kilometres, to form multi-element interferometres. Various model-fitting and map-making procedures have been used to estimate parameters of the brightness distributi... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Figure 1 shows the separation of the centres of the two components as a function of time. The point at 6 cm is taken from a number of measurements made in 1968 and 1969 (ref. 8). The source was only slightly resolved at that early epoch and θ was determined from the best-fitting double. The position angle was assumed t... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | The augular separation of the components of the double seems to be independent of wavelength over at least an octave. However, the detailed visibility curves show that the ratio of flux densities varies with wavelength; that is, the components have different spectra. 中文
The position angle (PA) of the double was determi... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Figure 6 of Schilizzi et al. (ref. 15) shows a succession of (u, v) diagrams with the observed lines of maxima and minima of the visibility function. The lines are not equally spaced; therefore, the source cannot be represented by a simple (that is, Gaussian) double. Furthermore, the relative spacings change with time,... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Further data exist at 2.8 cm for 1975 and 1976, but the character of the visibility function is different then from what it was earlier. The functions do not contain any clearly recognizable extrema (except at the origin), but drop rather smoothly to a “core” value. The brightness distributions may still contain “compo... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 3C120 varies rapidly in flux density and appearance, and has been observed frequently in an attempt to follow its variations7,15,21-25. Although many of the observations have been rather incomplete, in several cases very good data were obtained with 3 or 4 telescopes, and simple double models fit very well. The best of... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | We recognize two major epochs of expansion in Fig. 5, and have indicated them with straight lines whose slopes correspond to v/c=5 and v/c=8. At 1974.5 the 3.8 and 2.8 cm observations showed doubles of very different separation. No unique interpretation can be given for this, for the size and strength of the components... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Figure 6 shows the total flux density of 3C120 at λ=3.8 cm. This source varies more rapidly and has a greater fractional variation than 3C345 and 3C273. The largest outburst in Fig. 6 begins in mid-1972 and is coincident with the start of the first expansion shown in Fig. 5. The second expansion starts in early 1974 an... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | It is of interest to ask what fraction of all sources are superluminal, and whether statistical arguments can be made for or against any of the customary interpretations. These are difficult questions because adequate surveys do not exist at the short centimeter wavelengths, and VLBI surveying is particularly incomplet... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Nearly half the strong compact sources show a superluminal effect. This suggests that mechanisms which require us to be in an especially favorable position are unlikely to be at work. Luminous relativistically moving clouds are one such class, because to see them superluminally we have to be within a small solid angle1... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | No systematic contractions have been seen. The separation of components in a source is basically independent of wavelength from 2 to 6 cm, although the components may have different spectra. In 3C273, and perhaps in 3C120, we may have observed an epoch where component evolution produced different sizes at different wav... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | *Owens Valley Radio Observatory, California Institute of Technology, Pasadena, California 91125
†National Radio Astronomy Observatory, Green Bank, West Virginia 24944
‡Max-Planck-Institut fur Radioastronomie, Bonn 1, Federal Republic of Germany
§Netherlands Foundation for Radio Astronomy, Radiosterrenwacht, Dwingeloo, ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Legg, T. H. et al. Nature 244, 18 (1973).
Pauliny-Toth, I. I. K. et al. Nature 259, 17 (1976).
Shaffer, D. B. et al. Astrophys. J. 201, 256 (1975).
Clark, B. G. et al. Astrophys. J. Lett. 182, L57 (1973).
超光速射电源
科恩等
编者按
20世纪70年代,人们利用干涉测量法来观测星系和类星体时,发现从这些星系和类星体中心发出的物质团的运动速度似乎明显高于光速——从表面上看其数值违背了狭义相对论。一些天文学家据此认为类星体实际上更接近... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | ) 英文
在至少一个倍频程内,两个子源的角分离似乎都和波长无关。不过,详细的可见度曲线显示子源的流量密度比随波长变化;也就是说,两个子源的谱形是不一样的。 英文
我们利用图1中所有的观测结果得出双源的位置角(PA),这些观测数据是足够多的。位置角随着波长或时间没有明显的变化,一直保持在105°±3°。 英文
将图1中的速率外推到角分离为零的状况,表明“分裂事件”发生在1966年。图2显示了3C345在3.8 cm波段上的总流量密度。从1966年开始,流量密度有了大幅度的增加;流量在两年内成倍增长,此后一直很高。这些时间上的近乎重合表明爆发和膨胀的起源相同。 英文
图2. 3C345在λ=3.8 cm波段的总流量密度。1963到19... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 英文
3C120(z=0.033)
3C120在流量密度和外形上变化得很快,为了跟踪它的变化,对它的观测较为频繁[7,15,21-25]。尽管许多观测颇为不完整,但是有几个观测项目用三到四台望远镜得到了很好的数据,而且与简单的双峰模型拟合得非常好。这些观测中最好的一次是我们于1976.1在2.8 cm波段进行的观测,我们使用格林班克、戴维斯堡和欧文斯谷的望远镜观测到了5个确定得很好的极大和极小值。像3C345一样,分离得很好的高斯双峰模型精确拟合了所有的可见度数据。不过,3C120中的致密结构不像3C345中的那样产生几乎全部总流量。3C120中的致密成分处在一个更大的、未准确测量的结构里。 英文
在所有数据质量良好的情况下,位置角... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 英文
1972年在3.8 cm波段的一系列观测(参考文献17)可以看成3C279发生一次新的膨胀事件,因为在1972年3月和4月看到了一个微弱的不可分辨的核,而它到1972年11月变得可以充分地分辨开来。还一个可能是1972年的所有数据都来自一个三源系统,它的整体尺度不变,但是子源的流量密度在变化[17]。已经发表的数据跟任何一个模型都吻合,因此要区分这些模型就需要更多的数据。 英文
结果分析
超光速源在所有源中的比率以及是否存在统计上的论据来支持或者反对通常的解释,这些都是很有意义的问题。但是这些问题也都很难回答,因为在厘米短波上还没有足够多的巡天,并且VLBI巡天也特别不完整。不过,我们仍可以做一些评论。 英文
在λ=3.8 c... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 英文
(肖莉 翻译;何香涛 审稿)
New Hominoid Primates from the Siwaliks of Pakistan and their Bearing on Hominoid Evolution
D. Pilbeam et al.
Editor’s Note
The Miocene strata of the Siwalik Hills in Pakistan had yielded abundant fossils for decades, but the 1970s were especially rich. Pilbeam et al. document 86 new primate specimen... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Fig. 2. Top row, left to right: GSP 11708, 11704, 9977/01/05/9564. Bottom row: 11536/7, 13163, 4230, 9977/01/05/9564.
中文
More than 13,000 catalogued fossil specimens representing a diverse vertebrate and invertebrate fauna have been collected from more than 300 localities; 18 localities have yielded 86 new hominoid p... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Approximate ages can be assigned to the localities on the basis of faunal comparisons to dated sequences elsewhere in the Old World, and these are apparently supported by palaeomagnetic surveys which will be published soon. Locality 38 may be about 12 Myr old; 251 and 261 about 9.5-10 Myr old; and the rest of the sites... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | that the overall mammal community lacked a diversity of large mammals and had low numbers of grazing species, herbivores above 100 kg and arboreal species. By comparison with recent and Pleistocene faunas associated with riverine environments, this suggests woodland or bush habitats with open patches of grassland rathe... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | There is an extensive primary literature on Siwalik primates, and they have been mentioned and discussed many times2. Approximately 90 hominoid specimens representing more than 60 individuals are known from previous collections. The Potwar Plateau yielded some isolated teeth and a few jaws, the bulk from the Chinji For... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | At least one species of Ramapithecus, R. punjabicus (Fig. 1), is represented in Siwalik rocks; the genus is found in the Chinji and Nagri Formations, and possibly in rocks equivalent to the Dhok Pathan Formation. The probable age range is 13-8.5 Myr. 中文
The new material from the Potwar Plateau helps considerably in und... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | One partial molar from locality 311, GSP 7144, is tentatively assigned to Gigantopithecus, as is a previously described molar, GSI D175 from Alipur near Hasnot14. Both are probably 9.0-10 Myr old. Occlusal morphology is rather similar to that of Ramapithecus, and occlusal surface enamel is thick (about 3.5 mm on the ma... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | close in size to the corresponding bones of adult pygmy chimpanzees. This group includes a partial distal right humerus, GSP 6663, with parts of the capitular and trochlear surfaces preserved. Hindlimb specimens include a femoral head, GSP 6178, a femoral head plus part of the neck, GSP 11867, the proximal, mid-shaft, ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | group). It is significant that the Gigantopithecus humeral fragment and many of the Sivapithecus specimens come from locality 311; dental remains from that locality include our only Gigantopithecus specimen and five Sivapithecus indicus (Table 2). 中文
If the postcranial remains are correctly subdivided and if they are a... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | non-human higher primates, have relatively small cheek teeth with thin enamel, perhaps an adaptation to predominantly browsing diets. Pliocene and earlier Pleistocene hominids in contrast have large cheek teeth with thick enamel (Homo sapiens has evolved small cheek teeth relatively recently). Apes have large tusk-like... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | (3) Besides dryopithecines, other kinds of hominoids are present in the Old World middle Miocene. New material from Hungary17, Greece18, Turkey19, Kenya20 and China together with the specimens described here from Pakistan as well as earlier fossils from Europe and Africa show that thick-enamelled and (at least for thos... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | dryopithecines and pongines at least), and a postcranial skeleton showing numerous adaptations to habitual bipedalism. At least one of these species, by at least 2 and perhaps 2.5-3 Myr ago, made stone tools. 中文
It has been increasingly realised that these socalled Plio-Pleistocene hominids are not to be regarded merel... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | into which living large hominoids are normally subdivided, Pongidae and Hominidae, cannot be imposed on earlier Neogene species without suppressing important information and obscuring evolutionary concepts. 中文
A minimum of six clusters of species is needed to describe the diversity of Neogene large hominoids, and these... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Fig.4. Tentative stratigraphic-morphological distribution of large hominoid groups with possible phylogenies. P, Pongidae; D, Dryopithecidae; S, Sivapithecinae, R, Ramapithecinae; A, Australopithecinae; H, Homininae. (Sivapithecidae should be Ramapithecidae; note added in proof.)
中文
I suggest the following classifica... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | † Section of Gross Anatomy, Department of Surgery, Yale Medical School, New Haven, Connecticut 06520
‡ Department of Geology, Queen Mary College, London, UK
§ Division of Earth Sciences, University of California, Santa Cruz, California 95064
¶ Geological Survey of Pakistan, Quetta, Pakistan
Received 8 August; accepted ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Behrensmeyer, A. Earliest Man and Environments in the Lake Rudolf Basin (eds Coppens,Y., Howell, F., Isaac, G. & Leakey, R.) 163-170 (Chicago University Press, 1976).
Pickford, M. Nature 256, 279-284 (1975).
Simpson, G. G. Principles of Animal Taxonomy (Columbia University Press, New York, 1961).
巴基斯坦西瓦利克新发现的人猿超科灵长类动物... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 英文
我们和前人都从博德瓦尔高原的考察中挖掘出了大量属于脊椎动物与无脊椎动物动物群的化石,生物地层序列变得越来越清楚。特别在纳格里上层仔细采样,对于主要的分类组群(啮齿动物、食肉动物、猪科动物、牛科动物及马科动物)的新分析表明,这里和欧洲及西亚的属于晚瓦里西期与早图洛里安年代的遗址[3]非常相似。 英文
对于西瓦利克岩石学[4]、动物群[5-7]及植物群[8,9]的早期研究形成关于过去生境的假说。这些研究规模很大,涉及许多地点的动物群分析,且涵盖了广泛的地层范围,或利用并未严格归入到确定的地层学或古地理学格架之中的岩石或者植物群样本。只是最近才开展了更为充分的研究[10]。我们对岩石地层学、磁性地层学、沉积学、埋藏学、动物群及植物群... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 这些标本显示,腊玛古猿的门齿区十分窄,犬齿小,前面的前臼齿与犬齿紧紧地挤在一起,后犬齿齿列与下颌体向后分开。现在已知上下齿列的大部分牙齿。其某些特征值得注意:的舌侧齿尖虽然小但明显,其长轴与齿列中远端线大约45°。未受磨损的颊齿,特别是上颌的臼齿,与南方古猿及人属的颊齿极其相似。上下齿咬合面缩小,未受磨损的标本其颊(下颌齿)与舌侧(上颌)倾斜明显(对比参考文献13)。上下齿咬合面因磨损而变宽,几乎是平的,却仍未露出齿质。正如几个破损的标本(GSP 8926)所表现出来的以及通过对比未受磨损及磨损的程度类似的同源结构所看到的,这是因为上下牙咬合面的釉质非常厚(下颌骨颊侧齿尖,厚度介于2.5~3.0毫米之间)。下颌支相当粗壮;骨联合部的... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 英文
第一,西瓦利克的所有人猿超科动物有特征明显的颊齿,其上下齿咬合面的牙釉质十分厚。第二,都是真正的巨型牙,相对其身体尺寸,颊齿显得很大。在这两个特征上,西瓦利克人猿超科动物与上新世–更新世人科成员类似,而与猩猩科动物以及现在被归入森林古猿亚科(严格意义上的,见下文)的中新世人猿超科动物不同。第三,这些种类的上下齿咬合面在形态上都基本类似。 英文
主要根据前部齿大小,把西瓦利克人猿超科动物再细分为两组。西瓦古猿印度种拥有相对较大的门牙,与西瓦古猿西瓦种相像,犬齿二态性大;腊玛古猿与巨猿种的门齿相对较小,犬齿(可能)不突出并且(可能)适度二态。 英文
其他人猿超科动物材料
新的概念以及过去十年间所发现的新人猿超科动物的化石表明,需要... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 英文
现在已经越来越多地认识到这些通常所谓的上新世-更新世人科动物,虽然可被识别为人科,但不能仅仅被认为是“小型人类”,而应该从定性的方面上被看作是不同于中、晚更新世的人科动物的生物。它们是和真正原始种类不同的组。 英文
最古老的标本,其牙齿类似于南方古猿或早期人属种类的牙齿(显然不同于西瓦古猿或腊玛古猿组的牙齿),它们出自于肯尼亚的路奇诺与洛萨加姆,年代距今约500万年至700万年[24,25]。 英文
南方古猿与早期人亚科是在大约700万年前之后的这个时期内发生了分化;而迄今为止尚不明确西瓦古猿组与腊玛古猿组的种类。在非洲与欧亚大陆,猕猴,尤其是生活在更为开阔的空间的类型,第一次变得繁盛。 英文
综合分析
依据对人猿超科进化的现... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 英文
(田晓阳 翻译;林圣龙 审稿)
Pliocene Footprints in the Laetolil Beds at Laetoli, Northern Tanzania
M. D. Leakey and R. L. Hay
Editor’s Note
Since the 1930s, Louis Leakey and his colleagues had been persuaded that the Olduvai Gorge and the surrounding region would be productive of fossil human remains. This remarkable paper des... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Fig. 1. Map of the southern Serengeti and volcanic highlands showing the position of the Laetoli area.
中文
Description of the Footprints Tuff
The footprints tuff is divisible into two units of differing lithology and structure. The lower unit, 7-8.6 cm thick, is relatively uniform in thickness and is characterised by ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | On the basis of the available evidence a tentative history of the footprint tuff begins near the end of the dry season and continues into the rainy season. The first showers of ash fell on a relatively bare, nearly flat landscape with scattered Acacia trees. The ash layers which constitute the lower unit were cemented ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | The first site where footprints were observed (site A in Fig. 2) lies just south of the Garusi River in fossil Locality 6. An area of ~490 m2 has been exposed by natural erosion and by excavation. To the south-west, at a second site (C) there are ~156 m2 of the footprint-bearing tuff exposed. Both these localities were... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Avifauna
(1) Struthio sp. Two isolated prints at site (A). 中文
(2) Phasianidae, cf. Guinea fowl. Numerous tracks occur at all sites, generally in trails of four or more. They compare closely with tracks of the living helmeted Guinea fowl, common in the Laetoli area today. Average length of eight fossil prints 62 mm, of ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Fig. 5. Print of cercopithecoid fore and hind foot at site C.
中文
At site (F), in fossil Locality 10, there are at least four sets of tracks going in slightly different directions, as do the tracks of present-day baboons when they move in a troop. The average measurements of the hind feet in each of the four trails ra... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | It has been suggested that these prints might have resulted from the superposition of a hind on forefoot impression, or vice versa, either of a quadrupedal animal or a knuckle-walking primate. Careful examination of the original prints in situ reveals no indication of superposition, while the last interpretation invoke... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | toes (Figs 7, 8 and 9). 中文
Fossil record: two mandibles, parts of 2 maxillae, partial deciduous and permanent dentions as well as a partial infant skeleton and a number of isolated teeth have been recovered from the Laetolil Beds. They bear considerable resemblances to the material collected from the Afar in Ethiopia, ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | (3) Felidae. One trail of 12 prints at site (A), and several isolated prints appear to correspond in size to those of a serval cat. Average length/breadth/depth 65×52×13 mm. Average length of stride 29 mm. 中文
Fossil record: remains comparable to F. serval and F. caracal have been noted in the 1974-76collections. 中文
(4)... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Both Ceratotherium and Diceros must be represented among the many prints of rhinoceros, but no distinguishing features have been observed to date except on the basis of size. A trail at site (A) is one of the longest known, measuring 22 m in length. It contains 31 prints, 23 of which are double, with the hindfoot super... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Fossil record: only two Suidae are known from the Laetolil Beds, Potamochoerus sp. and Notochoerus euilus. Hylochoerus and Phacochoerus were previously believed to be present in the early fauna, but during 1974-77 have only been found in the more recent deposits. On size, the prints are probably of Potamochoerus, as No... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Bovidae
(1) Bovini cf. Simatherium kohllarseni. These prints consist of large, rounded and generally deeply indented tracks resembling those of the living African buffalo. They are clearly made by Bovini and can be attributed to S. kohllarseni, as this is the only bovine in the fossil record. The prints are represented... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | (4) Small antelopes and gazelles. Prints of dik-dik (Madoqua) are rare although dik-dik are the most abundant single species of fossil Bovidae. This anomaly may be explained by the fact that dik-dik are one of the Bovidae who do not require to drink water, subsisting on moisture from vegetation, while tracks of other B... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | With the hands free and available for purposes not connected with locomotion it is perhaps surprising that no form of artefact has been found. But the concept of tool-making may well have been beyond the mental ability of these small-brained creatures. Any “tools” or weapons used must have been solely of perishable mat... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 英文
莱托利尔层(图1、2)以凝灰岩为主要岩性,目前已知的最大厚度有130米,而且被分为上、下两个层位。几乎所有的化石都是从45~60米厚的上部层位中发现的。 英文
1975年在莱托利尔层的上部层位中发现了三个标志凝灰岩层[1]。其后,又辨识出了12处以上分布广泛的空落凝灰岩(图3),它们使不同化石点的地层的详细对比成为可能。 英文
图1. 莱托里在南塞伦盖蒂和火山高地中的地理位置图
英文
足迹凝灰岩描述
足迹凝灰岩可以分为两种不同的岩性和结构。在下部层位中有7~8.6厘米厚的凝灰岩,它们厚度相对统一,而且还以广泛分布的相同厚度的火山灰层为特征,这些火山灰层的表面上普遍有雨痕。在上部层位,凝灰岩通常有5~7厘米厚,在下部层位较... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 英文
倍足纲
一条长约20厘米的单独的足迹见于遗址(A)。 英文
化石记录:出土于第4化石地点的一小段蜈蚣化石。 英文
鸟类动物
(1)鸵鸟属未定种。两个单独的脚印见于遗址(A)。 英文
(2)雉科,珍珠鸡相似种。多个足迹见于所有遗址,一般每处有4列以上的足迹。它们与莱托里地区常见的现生盔珠鸡足迹非常相似。8个化石脚印的平均长度为62毫米,9个现生脚印的平均长度为60毫米。 英文
(3)相似的但小一点的足迹,脚印平均长度45毫米,可能是鹧鸪。 英文
化石记录:有很多鸵鸟蛋壳碎片,但没有骨骼化石。在第10化石地点发现了一窝蛋,蛋的大小与现在珍珠鸡蛋的相似。 英文
灵长目
猴科:其足迹见于3处。 英文
在遗址(C)有个单列足迹,由6个后... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 英文
化石记录:2件下颌骨,2件上颌骨残段,若干不完整的乳齿系和恒齿系,1个不完整的幼体骨架,还有一些单独的牙齿,均出土于莱托利尔层。它们与埃塞俄比亚阿法尔地区出土的材料有很多相似之处,尽管埃塞俄比亚材料要晚得多。 英文
兔科
所有遗址中都有不计其数的野兔足迹。 英文
化石记录:可以归入塞伦盖蒂兔属未定种的下颌骨和其他部位的化石非常多。 英文
食肉目
(1)灵猫科(属种不定):带有不可伸缩的爪的一系列小型食肉类的脚印在所有遗址均有发现。它们的脚印较浅,印痕相当模糊,长宽平均值为34毫米×27毫米。其他没有爪痕的小圆脚印可能属于麝猫。长宽平均值为28毫米×27毫米。 英文
化石记录:化石材料中有多种灵猫科成员,迪特里希曾记述过一些[3... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 英文
化石记录:在莱托利尔层中只有两种猪科成员,河猪未定种和南方猪兽。林猪和疣猪曾被认为出现在较早的动物群中,但是在1974~1977年的发掘中,只在较晚的沉积物中发现了它们。从大小上判断,脚印很可能是河猪的,因为南方猪是一种比现生的疣猪还要大的动物。 英文
长颈鹿科
(1)有3列同一个种的动物留下的足迹。它们分别由6、7、11个脚印组成。还有其他19个脚印被认为是长颈鹿的。在一条足迹中,这头长颈鹿每走一步都拖沓着脚趾,在地面划出一道长达96厘米的沟痕。这几列足迹的长宽深平均值分别为190毫米×151毫米×29毫米,202毫米×144毫米×10毫米,211毫米×150毫米×17毫米,205毫米×150毫米×28毫米。那些单独脚印的平... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | (这些人科动物)使用过的任何“工具”或武器肯定是完全用易腐材料制成的,因为在莱托利尔层中不仅缺乏人工制品,而且除火山喷出物外也没有其他石头。 英文
遗址的进一步勘探和材料的分析将持续到1979年,但莱托里显然将为认识上新世人科动物的生存环境提供独特的视角。 英文
感谢坦桑尼亚联合共和国允许我们继续在莱托里地区从事研究,感谢国家地理学会、华盛顿政府的经济支持,感谢坦桑尼亚文物部主管姆图里和管理员姆吉纳,感谢恩戈罗恩戈罗自然保护区管理局的帮助,感谢菲利普·利基和彼得·琼斯组织的野外季,感谢金特里博士、哈里斯和利基帮助鉴定牛科、长颈鹿科、灵长类动物和食肉动物的化石,感谢所有参加野外考察的人员。 英文
(张玉光 翻译;董为 审稿)
095... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | ft telescope at NRAO, Green Bank at λ 6 cm and λ 11 cm. This gave positions with typical accuracy 5-10 arc s and the identifications are estimated as ~80% reliable. 中文
The list of Porcas et al. includes the source 0957+561 which has within its field a close pair of blue stellar objects, separated by ~6 arc s, which are... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | negligible. On 1 April the spectral range was altered slightly by tilting the grating to cover the anticipated redshifted wavelength of Mg II λ2798 which was just beyond the limiting wavelength on previous nights. 中文
Table 2. List of IIDS observations with 2.1 m telescope
中文
The spectra obtained on 1 April are shown ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | redshift of a broad line of somewhat irregular shape. The mean values of the redshift from the C IV and C III] emission lines are 1.4054 for A and 1.4047 for B, the difference being within the errors of measurement. 中文
Fig. 2. IIDS scans of 0957+561 A(a) and B(b). The data are smoothed over 10 Å and the spectral resol... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Table 4. Wavelengths, identifications, and derived redshifts from image-tube spectra, 2.3 m observations
中文
Fig. 3. Microdensitometer tracings of portions of the spectra of 0957+561 A and B. Original dispersion of the plates was 47 Å mm–1. The solid lines mark the position of absorption features in the two QSOs and t... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | The image tube data on the C IV emission lines give a velocity difference ΔVem(B – A) of +265 km s–1. This is also subject to the zero point error, but the major source of error is the uncertainty of ~1.5 Å (=120 km s–1) in estimating the position of each line centre. The IIDS data on the C IV and C III] lines permit t... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | gravitational lens. We shall consider this possibility after examining the more conventional explanation involving two distinct QSOs. 中文
In the conventional interpretation of two adjacent QSOs we must either regard it as a coincidence that the emission spectra are so nearly the same, or assume that the initial conditio... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | absorption in 3C286. 中文
The second class of absorption involves intervening clouds associated with a cluster in which the QSOs are embedded. The velocity differences between the emission and absorption systems of A, B are typical of this class, but we must either ascribe the agreement in redshift of the two absorption ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | The 0.3 mag difference between the two components requires that the amplification of QSO light is ~4 for the brighter image, and thus implies a normal luminosity for the QSO. (This is also suggested by the absence of a strong narrow component in the C IV emission which might be expected if the source were a strongly am... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | from A. 中文
Further observations would shed light on the gravitational lens hypothesis. If the flux from the object is variable, the light curves of the two images should be similar but with a relative time delay due to the difference in path lengths. The lag depends on the details of the geometry, but with the paramete... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | a gravitational lens. 中文
(279, 381-384;1979)
D. Walsh*, R. F. Carswell† and R. J. Weymann‡
*University of Manchester, Nuffield Radio Astronomy Laboratories, Jodrell Bank, Macclesfield, Cheshire, UK
†Institute of Astronomy, Cambridge, UK
‡Steward Observatory, University of Arizona, Tucson, Arizona 85721
Received 25 Apri... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 在对每个天体积分20分钟后,可以明显看出两者是有着几乎相同光谱的类星体,基于被认证为CIVλ1549和C III] λ1909的强发射线,可知红移大概是1.40。进一步的观测在3月29日及之后的夜里进行,具体细节列于表2。在29日和30日的晚上都对距离天体几角秒的无星天空进行了观测并作为校正,结果证实,一个天体对另外一个天体光谱产生的污染可以忽略不计。4月1日,通过将光栅倾斜,光谱范围出现了细微的改变,以便覆盖预期Mg II λ2798红移后的波长,这条谱线在之前的夜里刚好在波长极限之外。 英文
表2. 2.1 m望远镜的加强型析像扫描器(IIDS)观测结果列表
英文
图2中给出了4月1日得到的光谱。观测的谱线数据列于表3。这些... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 遗憾的是,在遮罩上原本用来限制显像管噪声的灰尘斑点,使该天体光谱中的Si II谱线彻底消失了。 英文
两条吸收线红移值之差对应的速度差Δ Vabs(B–A)仅有大约+45 km·s-1。然而,除了在估计这些谱线中心时的误差外,在某种程度上各底片之间确定波长的零点也会产生更大的误差,其典型量级为100 km·s–1。因此类星体A和B中吸收线对应的红移之差并不显著。 英文
C IV发射线的显像管数据给出的速度差ΔVem(B–A)为+265 km·s-1。这也与零点确定的误差相关,但误差的主要来源是在估计每条谱线中心位置时的不确定性,大约为1.5 Å(=120 km·s-1)。根据加强型析像扫描器对CIV和C III]光谱线给出的数据,可... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 类星体A和B的星等差值(表1)约为0.3星等,这已经被我们的观测所证实。 英文
对更明亮的像来说,两个部分之间0.3个星等的差要求类星体的光增强约4倍,这表明该类星体的光度是正常的。(如果这个射电源是一个强烈放大的塞弗特活动星系核,在CIV发射谱中可能会出现一个强而窄的发射线。)由于引力透镜的最大角度只有天体分开角度的8倍左右,所以我们不能期待天空中会有这种图像[6]。 英文
由简单的欧氏空间计算,如果造成引力透镜成像的物质远离类星体,那么我们估计在红移zL处其质量必须达到大约1013zLM⊙,并且要求其半径30 kpc。假设存在一个这样的星系,鉴于它在底片上毫无显示,可以得出zL的下限大约是0.1。然而,这样一个星系的中心必须处于... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | single-stranded DNA which then binds to double-stranded DNA and samples for homology. Once found, the filament causes an exchange of strands that yields recombined DNA. Given the ability of short DNA fragment to stimulate unwinding, Radding correctly speculates that recombination may be inducible. 中文
Single-stranded DN... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | DNA in forming complexes with single-stranded fragments4. Subsequently, we have confirmed that form II DNA is a substrate for the formation of D-loops by recA protein (see below). The latter observation strengthened the inference that recA protein has an unstacking or unwinding activity, which is the subject of this ar... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | when recA protein and ATPγS were incubated with form II DNA in the absence of any added single-stranded DNA before ligation, we observed the formation of a small amount of material with the electrophoretic mobility of form I (see Table 1, lines 1 and 2). Controls included the following variations of the mixture represe... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | incubated for 15 more minutes.
中文
To determine whether the compact closed DNA had a lower or a higher linking number than the DNA closed by ligase alone (form I′), we centrifuged the products of a similar experiment in an isopycnic gradient of CsCl and propidium diiodide (Fig. 3 and Table 1). In the absence of recA p... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Fig. 3. Decreased linking number of circular DNA sealed in the presence of recA protein and ATPγS; isopycnic centrifugation in CsCl and propidium diiodide7. a, fd form II DNA sealed in the presence of recA protein only (○), and in the presence of recA protein plus heterologous fragments of single-stranded DNA from ΦX17... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | In further experiments we made D-loops by incubating recA protein with fd form I DNA and fragments of fd single strands in the presence of ATP4. Measurement by electron microscopy of 22 D-1oops with one or two single-stranded tails showed that the mean length was 416±45 nucleotides. (We were unable to distinguish the d... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Unwinding is supported either by heterologous or homologous single-stranded fragments (Fig. 4a, b). Circular single-stranded DNA, which does not form D-loops, promoted unwinding (Fig. 4d). Double-stranded restriction fragments were inactive, but their boiled products were active (Fig. 4f, g). This observation indicates... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | ligase was slightly positively superhelical under the conditions of gel electrophoresis (for example lane c) whereas closed circular DNA relaxed by calf thymus topoisomerase had a titrable superhelix density close to zero (for example lane k). We used 1% agarose gels, 16 cm×16 cm×0.3 cm in E buffer, which contained 40 ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | that case, from linear phage P22 DNA10. 中文
The formation of D-loops by form II DNA suggests that recA protein unwinds DNA in the presence of ATP as well as in the presence of the analogue, ATPγS. 中文
Discussion
Other experiments have shown that ATPγS competitively inhibits the ATPase activity of recA protein and blocks ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Mutants of recA are pleiotropic, they affect not only recombination, but also a set of inducible functions, the so-called SOS functions13; these include error-prone repair, inactivation of phage repressors and the synthesis of recA protein itself (for reviews see refs 14, 15). Damaged DNA or blocked replication are ind... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | certain other proteins that bind to DNA. 中文
A further inference from the similar effect of single strands and oligonucleotides on recA protein is that recombination may be inducible to some extent. Induction of synthesis of recA protein by single strands would provide the requisite amounts of protein to form D-loops, a... | 400套付费套装书 |
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