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C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | synthesized and then combined) corresponding to the intermediate products (up to four cycles) shown on the left. Lane 3 illustrates the products of the final ligation. The portion of the gel containing the 80-mer circle in this lane was lost during manipulation. The top most band in this lane contains a mixture of the ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | product corresponds to a single or multiple cycles of the belt (octagonal prism, dodecagonal prism, and so on) may be determined by the size of the U or D strand: at the concentrations used (10 nM in belt), the cube is the main product (Fig. 4, lanes 10 and 11). 中文
The side of the belt facing the reader at the branch p... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | Chen, J.-H., Kallenbach, N. R. & Seeman, N. C. J. Am. Chem. Soc. 111, 6402-6407 (1989).
Cohen, S. N., Chang, A. C. Y., Boyer, H. W. & Helling, R. B. Proc. Natl. Acad. Sci. U.S.A. 70, 3240-3244 (1973).
Seeman, N. C. J. Biomol. Str. Dyns 8, 573-581 (1990).
Seeman, N. C. J. Biomol. Str. Dyns 5, 997-1004 (1988).
Wang, J. C... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | 图1中所显示的五步是针对上述方法的失败而采取的对策。 英文
图1.立方体状物体的合成路线。此流程图对正文中提及的各条链进行了标注。数字代表各链的编号。我们遵循如下惯例:当一个新的链由于连接而形成时,对它的标注从一个或多个数字变成它在最终对象中所在位置对应的字母。例如,链1在刚合成时是一个线形分子,但是在成环后则记为L。最终立方体中6个链记为L(左)、R(右)、U(上)、D(下)、F(前)和B(后)。为清晰起见,对链与链之间螺旋的描述仅限于每条棱的中心部分,这遵循此前的惯例[7]。本路线图描述了单独各链在经过提纯后合成三维的三联通DNA物体的5个步骤(分为6个阶段)。第一步包括两个部分,完整长度的链1和链6环化分别形成L和R。接着,... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | 连接过程的目标产物与其他产物在非变性凝胶上是不可分离的(图2),但经过核酸外切酶III处理后,可以鉴别出三索烃的中间产物(L–F–R),表明黏性末端C和D成功地进行了双重连接。图3的变性胶表明在C和D连接后形成了大量耐核酸外切酶III的产物。图3还表明,在每个棱上有21对而不是20对核苷酸时得到的产物中完全没有L–F–R带。我们将变性凝胶中的索烃L–F–R带纯化,接着添加缺失的6个链将其重组,使其磷酸化。闭合后,立方体包含6个连接的环,相当于它的6个面,并记为左(L)、右(R)、上(U)、下(D)、前(F)和后(B)。图4显示了含有最终连接产物的变性凝胶。立方体与由5链组成的基准物一同迁移,但是可以在含1.25%双丙烯酰胺的13%变... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | 无论其形状是像立方体还是别的某种平行六面体,该物体带负电荷的棱之间极为紧凑的角度很可能使得它更接近于球形的角度[13]。这一立方体的合成使我们相信,合成更大、更复杂的物体[13,14]或许是可行的。 英文
(王耀杨 翻译;刘冬生 审稿)
Recent Variations in Arctic and Antarctic Sea-Ice Covers
P. Gloersen and W. J. Campbell
Editor’s Note
One of the major concerns about the threat of global warming was that the melting of ice sheets wo... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | Sea ice is an important part of the global climate system. The two key aspects of the complex and dynamic sea-ice covers are ice extents (the total area enclosed by the ice–ocean edges) and the area of open water within them, consisting of cracks called leads and large amorphous openings called polynyas, from the Russi... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | global ice extent. These trends were obtained from a very small sample of the total SMMR data set: that is, only the data at the time of the peaks of the winter extents and the troughs of the summer extents. 中文
The key question posed by this earlier paper, and left unanswered, was the following: if the maxima of the gl... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | An average of the polar ocean radiances between the 50° parallels and the ice edges was the radiation reference used for the detection and subsequent correction of SMMR instrument drift (P.G. et al., manuscript in preparation) in the four channels used in the calculations of sea-ice concentration3: the horizontally and... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | calculations by using both the equatorial and polar Earth radii rather than just the equatorial radius as was done in the Nimbus-5 studies. The net result of these improvements is that the SMMR ice-extent variations shown in Fig. 1 are ~7% greater in the Arctic than those reported earlier4, and about the same in the An... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | lines. The radiances are corrected for long-term instrument drift and variations with ecliptic angle. 中文
Trends in the Ice Covers
A band-limited regression (BLR) technique5 has been used previously to establish coherence between atmospheric carbon dioxide and global temperature10. We will use this technique to obtain ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | When this method is applied to the data on the extent of Arctic sea ice obtained from SMMR, a trend of –0.0315×106 km2 per year is found, with a standard deviation of 0.0143×106 km2 per year. Over the SMMR operational period of 8.8 years, this represents a 2.1±0.9% decline in the Arctic sea-ice extent. As the basis fun... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | trends are greater than the trends themselves. The results are summarized in Table 1 and illustrated in Figs 1 and 2. 中文
Table 1. Band-limited regression analysis of polar sea-ice covers
*Statistically insignificant. 中文
Fig. 2. Open water within the ocean–ice boundary (leads and polynyas) for a, the Arctic and b, the... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | lighting conditions has resulted in a fragmented data set of limited quality for the sea-ice extent. 中文
Whether or not the SMMR record of the decrease in the extents of the Arctic sea-ice cap signals a climate change is therefore an open question. These findings are, however, consistent with records of significant chan... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | We do know that sea ice exists in those parts of the Earth where global warming is expected to be the greatest. We also know that the sea-ice covers, with their high albedos and insulating effect between the polar atmospheres and oceans, are a key part of the climate machine. That the variations of the Arctic and Antar... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | Carsey, F. D. J. Geophys. Res. 87, 5809-5835 (1982).
Jones, P. D. et al. Nature 322, 790 (1988).
Hansen, J. & Lebedeff, S. Geophys. Res. Lett. 15, 323-326 (1988).
Lachenbruck, A. H., Cladouhos, T. T. & Saltus, R. W. Permafrost 3, 9-17 (ed. Senneset, K.) (Tapir, Trondheim, Norway, 1988).
Reynolds, W. R., Folland, C. K. ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | 上述变化趋势仅由整个SMMR数据库中的很小一部分样本得出,即仅采用了冬季冰范围达到峰值和夏季冰范围最小时的数据。 英文
早前的文章提出了一些关键问题但未给出答案:倘若全球海冰范围的最大值在8.8年中呈现为显著的减小趋势,那么除了年极值以外,南北两极的海冰范围曲线分别发生了怎样的变化呢?这种趋势的原因又是什么?我们认为,只有对所有海冰范围数据加以分析才能找出海冰范围各年的变化趋势,也许答案就在于各年海冰范围振荡曲线的形状中。 英文
在此我们给出SMMR监测到的关于南北两极海冰范围及其所包围无冰水面的全部数据,并且对所有数据作了仪器漂移校正和黄道角变化校正。考虑到原始数据的序列相关性,我们还给出了整个数据库的带限回归[5](BLR)分析... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | 简单地说,该方法需要一个多频带滤波器对数据进行平滑处理,然后再从已过滤数据中确定变化趋势,这些数据中的高频波动和季节性波动也已经被扣除。该方法的基础是矩阵U。
Uij=[sin 2πW (i–j)/π (i–j)];i, j=0, 1, 2..., N–1
(1)
其中0<W≤1/2为带宽参数;N=1,612代表观测结果的数量。设W=4/N。该方法中采用的带通滤波器由矩阵U的前8个特征向量及其对应的特征值组成,通过奇异值分解[11]可分别得到一个8×1,612的矩阵V和一个8×8的对角矩阵S。由于特征值的量级迅速下降,根据公式:
U = VSV′
(2)
可得到原始矩阵U的一个近似矩阵(在别的地方被称为截断序列回归[5])。V′代表... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | 北极海冰覆盖范围的减小已被认为是造成该变暖的可能原因之一[20],然而,与海冰范围变化相对应的冻土温度的升高所发生的时间要比这里所提到的时间长得多。另一方面,在这期间,并未发现有北半球海洋表面温度升高的证据 [21]。 英文
北极地区海冰范围明显减少,而在南极却没有相应变化,我们还不清楚这种不对称现象的原因。有趣的是,最近有人利用耦合海-气模型[22]模拟大气对全球CO2含量在100年内增加一倍的响应情况,结果显示,南北半球之间地表气温的上升也是不对称的,其中南极升温非常缓慢,而北极则快些。 英文
我们已经知道,海冰存在于地球上增暖最显著的地方。我们还知道,海冰具有很高的反射率,且在极地大气与海洋之间起着很强的保温作用,因此是气候系... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | SEISMIC wave speeds change with temperature and composition; so does the Earth’s density. It was expected, therefore, from the beginning of global seismic tomography (imaging in three dimensions of small deviations of wave speeds from a spherically symmetric reference model) that the method could provide the critical e... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | in the actual convection pattern than those predicted by calculations (for example in ref. 12). To make proper use of the information provided by seismic tomography and modelling of convection, we must know the spectral distribution of lateral heterogeneity in the mantle. 中文
Worse still, the low-order models may be bia... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | of Clayton and Comer9 contains a three-dimensional array of 57,000 cells, more than 14,000 times the number of parameters in PREM. But this is a “mathematical trickery”; the available data do not carry this much independent information. For instance, in their waveform inversion of over 2,000 seismograms, each of severa... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | An ideal data set for a two-dimensional study might consist of measurements of vertical ScS travel-time anomalies on a uniformly distributed, dense grid of points. In our “shadow” analogy, the rays are in this case at normal incidence to the screen and the problems resulting from oblique illumination are avoided. One c... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | Fig. 1. a, S and SS ray paths for the distance 50° (left), and SS ray path for the distance 150° (right). b, A comparison of an observed seismogram (24 March 1984) with the corresponding synthetic seismogram calculated for the spherical Earth model PREM15. Within the dashed lines is the isolated SS phase. c, The correl... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | We selected 429 earthquakes of appropriate size and distribution from the period 1977–89; these yielded 3,313 satisfactory measurements of the SS residuals in the appropriate distance range whose mid-path surface reflections are shown in Fig. 2a. The coverage is better in the Northern Hemisphere, but it is adequate for... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | Our choice of the SS phase was influenced by the results of Woodward22 and Woodward and Masters17,21 who measured travel-time differences between SS and S as well as between ScS and S. The differential travel-time approach has the advantage of being relatively insensitive to the source parameters and to the structure n... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | The first column gives the coefficients of spherical harmonics up to degree L=8 of the full (L=36) expansion of travel-time residuals which fitted the data with a r.m.s. error 1 s. The travel-time residual for these coefficients is δt = , with defined in equation 1. Columns 2–10 are spherical harmonic coefficients of t... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | calculated using the ray-tracing algorithm of Julian and Gubbins27 for exactly the same source–receiver pairs for which we have observations, and the residuals have been averaged at the same grid points as shown in Fig. 2b. The power spectra for both models are shown in Fig. 3b. It is clear that the overall distributio... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | high-wavenumber structure. 中文
Discussion
Figure 4a is a map derived by the synthesis of the spherical harmonic coefficients for degrees 1–36 obtained in a “damped” fit to the observed SS residuals. Figure 4b is the same as 4a but for the residuals predicted by model SH425.2. Figure 4c is also the same as 4a, but for th... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | Fig. 5. Power in each harmonic degree for the spherical harmonic expansions of δvp/vp given by the whole-mantle P-velocity model of Inoue et al.10. a, Layer 4 (148–238 km), b, layer 16 (2,566–2,900 km). 中文
The principal conclusion to be drawn from Figs 3 and 4 is that most of the power in the lateral heterogeneity spe... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | The third study is also by Woodward and Masters17. Their pattern of ScS–S residuals indicates the paramount influence of large-scale heterogeneity. Because the paths of ScS and S in the upper mantle are similar, the residuals must originate in the lower mantle. Through an ingenious test30, they demonstrate that the pri... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | The expansion of the plate velocity field in terms of spherical harmonic coefficients, with the spheroidal and toroidal components, may serve as a useful analogy, as the random measurement errors are not involved. Hager and O’Connell31 found that the power spectrum of these coefficients decreases rapidly, roughly as l–... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | Some final remarks with regard to seismological practice. The main reason why our experiment and those of Woodward and Masters17,21 or Zhang and Tanimoto28 have succeeded is that they were performed at relatively long periods. With a cut-off period of 32 s, each of our SS ray paths samples an average volume at least 1,... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | Woodhouse, J. H. & Dziewonski, A. M. J. Geophys. Res. 89, 5953-5986 (1984).
Clayton, R. W. & Comer, R. P. EOS Trans. Am. geophys. Un (Abstr.) 64, 776 (1983).
Inoue, H., Fukao, Y., Tanabe, K. & Ogata, Y. Phys. Earth Planet. Inter. 59, 294-328 (1990).
Clayton, R. W. & Comer, R. P. Terra Cognita 4, 282 (Abstr.) (1984).
Be... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | Forte, A. M. & Peltier, W. R. J. Geophys. Res. 92, 3645-3679 (1987).
Giardini, D., Li, X. & Woodhouse, J. H. Nature 325, 405-411 (1987).
Purdy, G. M., Dziewonski, A. M., Orcutt, J. A., Kanamori, H. & Duennebier, F. K. EOS Trans. Am. geophys. Un. (Abstr.) 70, 1230 (1989).
Acknowledgements. Much of our data set and the ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | 如果上述的其中一个说法是正确的,那么大部分的层析成像工作可能是错的,至少是误导人的。反过来说,这使得奥尔森等[2]的结论失效,这些结论让人误以为关于地球动力学的基本问题(板块构造的驱动机制)已经得到了概念性的解答。 英文
从考虑一维地球结构开始,地震层析成像经历了量和质的飞跃。比如,杰翁斯基和安德森[15]使用4个未知数得到球形对称PREM模型中的下地幔P波速度,而杰翁斯基[5]的低阶模型则使用245个参数描述同一区域的三维空间,参数增加了60倍。更大的改进则是典型的“块体”模型:克莱顿和科默[9]模型的下地幔部分包含了一个拥有57,000个单元块的三维阵列,比PREM模型中参数数量的14,000倍还多。然而这仅仅是个“数学假象”,... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | 北半球的覆盖率较好,但赤道以南的覆盖率对我们的目的而言也已足够。图2b展示了SS震相残差投影到与赤道上5°×5°相当面积的大致等距网格的情况。接着在伍德沃德和马斯特斯[21]的研究中,显示的数值是给定网格点5°范围内所有可用数据的平均值,并经过了地形、水深测量与地壳厚度的校正[22]。 英文
图2.a, SS震相中途反射点在地球表面的分布,每个圆点代表本研究3,313个数据点中的一个。b,投影到等距网格(赤道处5°×5°)的SS震相走时残差。残差使用半径5°的移动球冠进行了平滑处理。图中数据经过了地形、水深测量和晶体厚度的校正。 英文
1,452个球冠或者说90%以上的网格点都有SS震相残差数值。虽然只是通过对相邻点做平均来进行... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | 英文
利用此假设模型,我们严格按照上文所述的方法计算SS震相残差,图3d展示了“阻尼”与“精确”球谐拟合的谱功率。计算随机结构的SS残差等同于评价复合滤波器的响应。如果滤波器是“全通”的,那么图3d中从0到36阶的所有谱型应该大致是平的。实际情况是,只有约15阶以前是“全通”响应,之后就逐渐下降。这一衰减反映了沿射线积分与对球冠上数据进行平均的平滑作用。这些谱与图3a中功率在l=6处突然下降的观测谱明显不同。合成谱在高的角阶数处有更多能量,因此通过积分平滑不足以掩盖高波数构造的存在。 英文
讨论
将实测SS残差进行“阻尼”拟合,获得1到36阶球谐系数,综合得到图4a。图4b的做法与图4a相同,但残差是通过SH425.2模型预测的。图... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | 黑格和奥康奈尔[31]发现这些系数的功率谱以l–2的速度迅速衰减,正如SS谱,解释如下:速度场受少数几块具有恒定速度的大板块支配,导致了低能量。在二维情况下,以l–2的速度衰减的功率谱代表间断面。尽管单个的系数在较高的l值处很小,然而由于是同相位,所以它们的叠加效应会很大。 英文
我们认为我们的结果可以进行如下解释。速度异常场受水平维度为几千公里的实体所支配。在这些实体内,速度异常的变化平缓,速度在边界处可能会突然变化。而且,可能存在有限数量的小尺度异常,其形状是平面的(俯冲带)或线性的(地幔柱),但是和这些特征相关联的总功率不足以对合理进行的“低阶”反演结果造成偏差。 英文
这些结果给地幔对流建模增加了约束条件。黑格等[32]及福... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | The synthesis of molecular carbon structures in the form of C60 and other fullerenes1 has stimulated intense interest in the structures accessible to graphitic carbon sheets. Here I report the preparation of a new type of finite carbon structure consisting of needle-like tubes. Produced using an arc-discharge evaporati... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | certain regions of the electrode. The electrode on which carbon was deposited also contained polyhedral particles with spherical shell structures, which were 5–20 nm in diameter. The needle structures were examined by transmission electron microscopy (electron energies of 200 keV). 中文
High-resolution electron micrograp... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | lowers the bond energy. A similar effect of the bending on bonding energies might apply here. One of the key questions about the tubular structure is how the ABAB hexagonal stacking sequence found in graphite is relaxed, as it is impossible to retain this ideal graphite structure for coaxial tubes. There should be a sh... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | The {hk0} patterns as a whole show mm2 mirror symmetry about the needle axis, and consist of multiple sets of {hk0} spots. For example, three sets of (hk0) spots seem to form ring patterns, only (100)- and (220)-type spots being seen (Fig. 3a). The diffraction pattern was obtained from a single tube consisting of seven... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | the sheet with respect to the needle axis. In other words, the orientation of a hexagon sheet can be determined uniquely by referring to the needle axis. If hexagons A and B coincide with those labelled C and D, the needle axis will be along [010] and thus there will be no spiral rows of hexagons. This has, however, ra... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | the electron diffraction patterns. A systematic change in sheet orientations was confirmed by (h0l)-type lattice image observations. The question of whether the systematic variation in the rotation angles in successive tubules acts to stabilize the structure remains to be answered. 中文
The tips of the needles are usuall... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | Speck, J. S., Endo, M. & Dresselhaus, M. S. J. Cryst. Growth 94, 834-848 (1989).
Tibbetts, G. G. J. Cryst. Growth 66, 632-638 (1984).
Bacon, R. J. appl. Phys. 31, 283-290 (1960).
Iijima, S. J. Cryst. Growth 50, 675-683 (1980).
Iijima, S. J. Phys. Chem. 91, 3466-3467 (1987).
Kroto, H. W. Science 242, 1139-1145 (1988).
K... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | 弯折效应对于键能的类似影响在这里也适用。关于微管结构的一个关键问题是如何打破在石墨中存在的ABAB六方堆积序列,因为对于共轴管来说,要保留这一理想石墨结构是不可能的。一个管的周长比套在里面的管的周长多8~9个六元环的长度。无序的石墨堆积方式称为乱层堆积,但是还没有关于这种结构中堆积模式的详细报道。这里的论述也适用于早先谈到过的球状石墨颗粒[6]。 英文
对于由单个碳管状物获得的所有电子衍射图(图3),都已经根据六方对称性用{h0l}和{hk0}对衍射点进行了指标化。当管轴垂直于[001]轴时,图案中总是呈现出强的(00l)晶面衍射点,这验证了石墨管共轴排布的观点。如图2所示,每根管的两个边缘部分(用阴影表示,标记为“V”)将会选取使... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | 我倒是曾经见过围绕管的同心原子台阶(我不能确定它们是螺旋状的)。基于对管状物形态的上述新实验发现,我为微管形管状物提出一种新的生长模型。即单根管本身即可在管末端发生螺旋形台阶生长(图4b)。值得一提的是,螺旋形生长台阶具有手性——这由六边形单层所决定。生长机制似乎遵循一种螺旋位错模型,它与为常规晶体所建立的模型类似,但是就当前晶体具有圆柱形晶格的意义而言,螺旋结构完全不同于螺旋位错。 英文
(王耀杨 翻译;李彦 审稿)
A Planetary System around the Millisecond Pulsar PSR1257+12
A. Wolszczan and D. A. Frail
Editor’s Note
Mill... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | possibility that a non-negligible fraction of neutron stars observable as radio pulsars may be orbited by planet-like bodies. 中文
THE 6.2-ms pulsar PSR1257+12 (Fig. 1) was discovered during the search at high galactic latitudes for millisecond pulsars conducted in February 1990 with the 305-m Arecibo radiotelescope at ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | A least-squares fit of a simple model, which involved the pulsar’s rotational period, P, and its derivative, Ṗ, as free parameters and the fixed VLA position (Table 1), to the timing data spanning the period of 486 days resulted in post-fit residuals shown in Fig. 2a. The residuals, which measure the difference between... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | the pulsar spin axis10,11 or any magnetospheric phenomena at the level that could lead to periodic TOA variations of the measured magnitude. Consequently, the most plausible remaining alternative is that PSR1257+12 has two low-mass companions and that their orbital motion is responsible for the observed TOA variations.... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | Fig. 3. Period variations of PSR1257+12. Each period measurement is based on observations made on at least two consecutive days. The solid line denotes changes in period predicted by a two-planet model of the 1257+12 system. 中文
The high quality of the two-companion model fit to the pulsar timing data covering several ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | (~0.4 AU) due to the neutron star’s rotational energy loss (, where I is the moment of inertia and ω = 2π/P) is ~4 × 107 erg cm–2 s–1 . This is ~30 times the solar constant and corresponds to a black-body temperature of ~670 K, which is similar to the measured dayside surface temperature of Mercury (see, for example, r... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | companion in a manner different from the disruption of a binary system caused by a supernova explosion and to retain enough circumpulsar matter to form planet-sized objects. 中文
Within the constraints provided by the observational evidence, it is tempting to postulate that the 1257+12 system simply represents one of the... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | * National Astronomy and lonosphere Center, Arecibo Observatory, Arecibo, Puerto Rico 00613, USA
† National Radio Astronomy Observatory, Socorro, New Mexico 87801, USA
Received 21 November; accepted 9 December 1991.
References:
Bhattacharya, D. & van den Heuvel, E. P. J. Phys. Rep. 203, 1-124 (1991).
Wolszczan, A. IA... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | Acknowledgements. We thank D. Backer, P. Nicholson, B. Paczyński, F. Rasio, S. Shapiro, J. Taylor and S. Teukolsky for discussions. We also thank J. Taylor for making available the Princeton Mark III processor. Arecibo Observatory is part of the National Astronomy and lonosphere Center, which is operated by Cornell Uni... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | 很明显,对假设的两个双星周期性中的一个进行拟合,得到的拟合后残差正好显示出另一个周期性。这表明PSR1257+12的脉冲到达时间实际上受到两个相互独立的周期性影响。进一步的仔细分析显示周期性和射电频率无关,在阿雷西博利用同样数据接收仪器对其他毫秒脉冲星进行常规观测,它们的测时残差没有显示这种效应。 英文
表1.PSR1257+12系统的参数
英文
毫秒脉冲星是极为稳定的转子。对1.5毫秒脉冲星1937+21(参考文献6)这样的天体进行系统的测时观测,并没有发现任何测时噪声、准周期TOA变化和经常在年轻脉冲星族中发现的自转突变(自转突变被认为同中子星星震学相关[7])。PSR1257+12的TOA变化幅度和频率无关,这点排除了传播... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | 由于原初行星不大可能在这样的演化中存活下来[22],观测到的1257+12系统可能是由在脉冲星的双星历史末期或之后产生的“二代”行星组成。因为在小质量双星中不大可能发生第二次超新星爆发,这样的行星才可能形成环绕一颗年老中子星运动的稳定天体系统。另外一个重要的演化限制是观测到的行星轨道的极小的偏心率(e约等于0.02)和轨道周期的近共振比率。这些特征表明行星是从某种吸积盘产生的,这种吸积盘能够自然提供圆化轨道的途径,从而让它们接近于3/2共振[12]。因此,任何生成环绕毫秒脉冲星的行星系统的可能机制都必须提供一种移除恒星伴星的途径,这种途径不同于超新星爆发所引起的双星系统的瓦解,并且能够留住足够多的环绕脉冲星的物质来形成行星尺度的天体... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | devices. 中文
Photochromic materials, whose optical absorption properties change in response to light, are important for a number of technological applications. A stable, reusable photochromic thin-film could be used, for example, in optical displays and high-density memories. Thin films of some transition-metal oxides ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | cm2. Because we did not add any redox couple into the electrolyte, the reactions occurring at the counter-electrode were probably the reduction and oxidation of water present as an impurity in the electrolyte. 中文
Because freshly prepared MoO3 is colourless and transparent, it does not show photochromism on irradiation ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | Fig. 1 Absorption spectra of a MoO3 thin film. a, MoO3 thin film as prepared by vacuum evaporation (curve A); spectrum taken after polarization at –0.1 V versus Ag/AgCl for 3 min in 0.1 M LiClO4/propylene carbonate solution (curve B); and taken after the film in curve B was irradiated with visible light (λ 500 nm) for ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | completely decoloured, it was no longer sensitive to visible light. But if the colourless film was slightly blued again, it became sensitive to visible light. 中文
Fig. 2 The absorbance change (∆abs) of MoO3 thin film at 800 nm during coloration and decoloration. The electrochemical polarization was done at constant cur... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | At present the origin of the intermediate metastable state is not known, although the key to the problem is probably that the visible-light-sensitive photochromism is observed only with films slightly blued by the electrochromic reaction and not by the conventional band-gap photochromic reaction. One possible explanati... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | J. N. Yao, K. Hashimoto & A. Fujishima
Department of Synthetic Chemistry, Faculty of Engineering, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113, Japan
Received 21 August; accepted 3 December 1991.
References:
Deb, S. K. Phil. Mag. 27, 801-822 (1973).
Deb, S. K. J. appl. Phys. 37, 4818-4825 (1966).
Yao, ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | 随后将电解预处理的薄膜在空气中用可见光照射10 min。照射部分变成深蓝色(曲线C):在800 nm处的吸光度变化约为0.3。利用近红外光(波长 nm)照射也得到了相似的颜色增强效果。这表明即使采用宽吸收带(500~1,000 nm)激发也可以诱导电解预处理MoO3薄膜的光致变色反应。因为在电解池和光源之间加入可阻断热量的滤光片或者在80°C的条件下进行可见光照射都没有影响颜色增强的程度,因此可以排除由于热效应导致的颜色增强。 英文
图1.MoO3薄膜的吸收光谱。a, 新制备的真空蒸镀MoO3薄膜 (曲线A);在0.1 M LiClO4/碳酸丙烯酯电解液中,将A样品在相对Ag/AgCl电极-0.1 V条件下极化3 min(曲线B)... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | 英文
(马颖 翻译;姚建年 审稿)
The C. elegans Genome Sequencing Project: a Beginning
J. Sulston et al.
Editor’s Note
Here British biologist John Sulston and colleagues describe developments during the first year of the collaborative Caenorhabditis elegans genome sequencing project. Sulston believed the small genome would prove a ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | animal genomes intermediate in size and complexity between those of yeast and man will help us to understand the more complex features of mammals. 中文
The genome of the small nematode C. elegans is a good candidate for complete sequence analysis5. This organism has been used to investigate animal development and behavio... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | We have embarked on a project to determine the entire sequence of the nematode genome. The region where we began is the centre of chromosome III (Fig. 1). There is good cosmid coverage over most of several megabases, and the few areas lacking cosmid coverage are spanned by YACs. The region lies in the central gene-rich... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | To collect the sequence data, we relied largely on two fluorescent-based sequence-gel readers, the Applied Biosystems ABI 373A and the Pharmacia ALF, which provide data directly in machine-readable form. All data were transferred to Unix-based Sun workstations. A display editor was developed to allow rapid clipping of ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | Once the final sequence was obtained, the databases were searched for similarities using the algorithm BLAST35. In addition, we have started to interpret the sequence directly. The program GENEFINDER (P.G. and L.H., unpublished) uses a statistically rigorous treatment of likelihoods to find possible genes. Other featur... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | The overlap of the manual, radiolabelled sequence with the fluorescent shotgun reads in ZK637 amply confirms the fidelity of the fluorescent method. The accuracy of the base calling was tested by comparing a sampling of individual sequence reads with the final edited sequence (Fig. 2). Generally the only errors found i... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | should be similar in the cosmid sequences presented here. 中文
The accuracy of the final sequence is difficult to estimate without extensive independent tests, but several factors give us confidence that the fidelity to the true genomic sequence is high. All sequences were determined at least once on both strands, with ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | transposase TcA of the nematode transposon Tcl, and the host protective factor of the parasitic nematode Trichostrongylus colubriformis. Less extensive but still highly significant similarities (BLAST scores of >100 over one or two exons) were found with the 50S ribosomal protein L11 and the neutrophil oxidase factor. ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | shading within the same block, but has not been confirmed by experiment. PNMTase, phenylethanolamine-N-methyltransferase; phox: neutrophil oxidase factor. 中文
Fig. 4. The similarities of the predicted genes to previously known genes are shown in detail. The gene with the highest similarity to the proposed nematode gene... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | strandedness of exons, we would estimate B0303 contains 14 genes, ZK637 12 genes and ZK643 6 genes. Transcript analysis will be required to test these predictions. Several studies have already centred on genes in the region. The gene sup-5 (ref. 37) had been mapped close to the end of B0303; indeed, the B0303 sequence ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | tandemly repeated; the same motif is found at the fragile X site39-41. Some 20 copies of a 94-bp consensus sequence were found dispersed throughout the three cosmids, many in inverted pairs separated by up to 130 bp. Some copies showed a good match to the consensus (80–90% identity), whereas others diverged strongly or... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | The number of predicted genes in these cosmids is higher than would have been expected on the basis of genetic estimates of essential gene number42 and on a previous transcript analysis around the vitellogenin genes43. The high gene density (one every 3–4 kb) may arise in part because the sample comes from the gene-ric... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | on which to design experiments to test function. 中文
Each cosmid sequence is submitted, as it is completed, to the databases. In addition, the sequence is entered in the C. elegans database being developed as part of this project. Here the sequence will be available in conjunction with the physical map, the genetic map,... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | Received 3 September 1991; accepted 4 February 1992.
References:
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Cantor, C. R. Science 248, 49-51 (1990).
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Hunkapiller, T., Kaiser, R. J., Koop, B. F. & Hood, L. Science 254, 59-67 (1991).
Roberts, L. Science 248, 1310-1313 (1990).
Brenner,... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | Dear, S. & Staden, R. Nucleic Acids Res. 19, 3907-3911 (1991).
Hillier, L. & Green, P. PCR Meth. Appls 1, 124-128 (1991).
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Mizusawa, S., Nishimura, S. & Seela, F. Nucleic Acids Res. 14, 1319-1324 (1986).
Hawkins, T. L.... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | Kaneda, N. et al. J. boil. Chem. 263, 7672-7677 (1988).
Sasaoka, T., Kaneda, N., Kurosawa, Y.,Fujita, K. & Nagatsu, T. Neurochem. Int. 15, 555-565 (1989).
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Prasad, S. S., Harris, L. J., Baillie, D. L. & Rose, A. M. Genome 34, 6-12 (1991).
Leto, T. L. et al. Scienc... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | 全部基因组序列于6年后发表,使得秀丽隐杆线虫成为第一个完成全基因组测序的多细胞生物。在2003年发表的人类全基因组序列从本项目建立的技术中获益良多。 英文
本项目的长期目标是阐明秀丽隐杆线虫全基因组序列。第一年,研究者们建立了测序方法,并制定了一个适用于大规模测序的策略。在初始阶段所测序的三个黏粒(cosmid)中,基因之丰富令人惊讶,其中许多都有哺乳类的同源基因。 英文
由于认识到人类基因组可以被完全测序,激发出人们对基因组分析的巨大兴趣[1,2],人们已经开始努力构建遗传和物理图谱[3]以及改进DNA测序的方法[4]。为追求这一伟大目标,有必要对基因组较小且易于实验操作的模式生物进行测序和分析。这些模式生物将作为前期实验系统... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | 在获得100~350个测序片段(理想数据量最终取决于相关测序费用,该统计结果尚未建立;表1),并采用施塔登氏(Staden’s)拼接程序[28]拼接成重叠群(contigs)之后,该项目转入了定向的消除缺口与完成阶段。作为一个初步定向步骤,有时会从选定插入片段的另一端获取一个反向测序片段,以帮助建立关联、形成双链和消除缺口。进一步的定向测序需要定制的寡聚核苷酸引物,用OSP(寡聚核苷酸选择程序)[29]帮助选择引物。由于技术原因,法玛西亚公司ALF对来自定制引物的测序结果更为方便[30]。在消除缺口和形成双链之后,有时必须获取更多的测序片段来解决不确定的序列,通常采用不同的化学方法[31,32]。就任何所关注区域,通过编辑程序回溯原... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | 最令人惊讶的是,ZK637的22~26 kb区域和大鼠细胞液泡质子泵的116K亚基(相对分子量为116,000)具有高度相似性(图4)。两者的相似处分布于若干区段,GENEFINDER将其读取为外显子,从这种有838个氨基酸的蛋白质的第14残基延伸至第824残基处。这两段序列的氨基端的一半高度保守;在其中一段,139个残基中有99个是相同的(71%),而在第二段,314个残基中有223个是相同的(71%),且在序列比对中没有出现空缺。而羧基端的一半相似性较低,但含有与我们推测的8个跨膜结构域相似的序列。其他具有广泛相似性的基因包括乙酰辅酶A乙酰基转移酶、谷胱甘肽还原酶、砷驱动泵的三磷酸腺苷酶、线虫转座子Tc1的假想转座酶TcA以及寄... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | 在测序开始前,通过转化恢复试验(transformation rescue),已知基因lin-9(文献38)和unc-32(文献6)位于ZK637中。已经表明,基因lin-9与ZK637的20.2–16.6区域底链的预测基因相对应,并使用互补DNA序列来优化GNENFINDER分析得到的预测(比特尔和霍维茨,个人通信)。从遗传学位置得知,unc-32可能是紧临lin-9基因右侧的基因之一。 英文
我们也对序列中的重复序列进行了分析。大片段的几乎完美的反向重复序列(465/468)位于B0303的15 kb位点附近的侧翼(图3),与TcA转座酶有相似性。随后的分析表明,这一区域代表了与Tc1相关的转座子Tc3的一个拷贝(施奈德、柯林斯... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | 英文
随着投入不断增加,今后两年我们将对该策略进行检验:我们将在第一年测序800 kb,在第二年测序2,000 kb。采用目前方法进行生产,估计成本为每碱基1美元,随着我们转向类似于生产的模式,预计成本将下降。随着经验增多、新方法出现和自动化程度提升,操作时间将缩短。例如,我们正在采用更迅速而便宜的模板制备方法。制造商也正在开发更高通量的测序设备,通过增加每次运行的样品数量,或是缩短运行时间。通过减少试剂使用量和降低试剂成本,寡聚核苷酸的成本正在稳步下降。在规模化的运作模式下,某些试剂本地生产也将节约成本。伴随着这些改进,把测序成本降低到每碱基0.50美元看来是可现实的。 英文
(周志华 翻译;吕雪梅 审稿)
Tectonic F... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | drawdown of atmospheric carbon dioxide, leading to global cooling3,4. These hypotheses have provoked controversy in a wide range of fields. Geophysicists Molnar and England5 put forth the inverse proposal that climate changes were responsible for the inferred increases in elevation and erosion. Geochemists6-10 argued w... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | Oxygen isotope data for the past 55 Myr (refs 14, 15) show a long-term increase in δ18O values punctuated by times of relatively rapid change (Fig. 1). The sharp increase in isotopic values in the early Oligocene (~36 Myr BP) may reflect the first major ice-growth event on Antarctica16, which followed roughly 20 millio... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | Fig. 1. Compilation of benthic δ18O measurements from Deep Sea Drilling Program sites spanning the past 70 Myr. The long-term increase in δ18O values reflects cooling of the deep ocean and growth of ice sheets at high latitudes (after ref. 14). δ18O = [(18O/16O)sample / (18O/16O)standard –1], where standard is PDB. 中文
... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | when Antarctica separated from South America and Australia has often been invoked to explain the rapid cooling and glaciation of Antarctica in the Cenozoic28,29. These investigators suggest that greater meridional heat transport before the initiation of circum-Antarctic ocean circulation resulted in higher sea surface ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | and because its unique size and location make it central to our hypotheses. 中文
With a mean elevation of almost five kilometres and an area half the size of the United States, the Tibetan plateau is the most imposing topographic feature on the Earth’s surface. It formed as a result of the collision of the Indo-Australia... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | differences in the climates calculated by the model. For instance, relative to the zero-topography experiment, the GCM run with modern topography shows a decrease in summer precipitation around the Mediterranean caused by increased subsidence of dry air masses and stronger northeasterly winds. Similarly, the spread of ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | It is widely accepted that changes in the concentration of radiatively important trace gases in the atmosphere (particularly CO2) can alter the Earth’s climate. A direct link between atmospheric temperature and CO2 concentration is observed throughout the 140,000-year Vostok ice-core record of the last glacial–intergla... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | formulated, their model produces higher CO2 levels in the Cretaceous because of (1) more rapid seafloor spreading and volcanic outgassing of CO2 at that time, and (2) a decrease in the land area available to chemical erosion, because of globally higher sea levels. The higher sea levels are in large part related to fast... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | abundance of easily weathered sedimentary silicates derived from uplifted passive margin sequences (weathering of carbonates does not ultimately alter atmospheric CO2), the orographic concentration of rainfall on mountain slopes, and steep slopes which flush away mechanical and chemical erosion products, constantly exp... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | On the basis of these and similar observations, we propose that late Cenozoic uplift of the Himalayan region and Tibetan plateau would have resulted in regionally, and hence globally, higher chemical erosion rates, causing a drawdown of atmospheric CO2 and global cooling. The timing of this tectonically driven CO2 decr... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | weathered carbonates. Measurements of the isotopic composition of Himalayan limestones are needed to confirm this hypothesis. A third strontium input to the ocean, from redissolution of marine carbonates (average value 0.7084; ref. 51), buffers the isotope ratio of the oceanic strontium reservoir towards the integrated... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | granites and gneisses into easily weathered carbonates8. Palmer and Edmond8 attribute the unusually high strontium isotopic composition of the Ganges–Bramaputra river system to such “orogenic” repartitioning. But a related study53 of the Ganges–Bramaputra headwaters proposes that the high 87Sr/86Sr ratios in these rive... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | Although the evolution of the seawater strontium curve is consistent with a pronounced increase in chemical weathering since the Eocene, this interpretation is clearly not unique; a considerable fraction of the 87Sr/86Sr change could be due to variations in the isotope ratios in source rocks. The interpretation is furt... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0305. 《自然》百年科学经典(英汉对照版)(第七卷)(1985-1992).epub | .epub | 41,865,664 | 2025-09-26T19:07:39.767346 | has a small but significant impact on the cycling of atmospheric CO2. On average over the Phanerozoic, roughly 80% of the carbon removed from the ocean–atmosphere system was deposited as carbonates, whereas ~20% was buried as organic matter61. Because organic matter is extremely enriched in 12C during photosynthesis, a... | 400套付费套装书 |
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