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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 | Kline Biology Tower, Yale University, New Haven, Connecticut 06520
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Weiss, M. C., and... | 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 | Bobrow, M., Madan, K., and Pearson, P. L., Nature New Biology, 238, 122 (1972).
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Ruddle, F. H., Ricciuti, F., McMorris, F. 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 | Migeon, B. R., and Miller, O. S., Science, 162, 1005 (1968).
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Ruddle, F. H., and Chen, T. R., in Perspectives in Cytogenetics (edit. by Wright, S. W.,... | 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 | 埃弗吕西和他的同事们经过一系列的研究发现不同物种的细胞之间可以进行杂交组合[2],并且来自一个或者两个亲代的染色体组可能会从杂交细胞中丢失或者分离[3]。韦斯和格林[4]首次实现了体细胞融合–分离系统在人类基因作图中的实际应用(见下文)。其他研究者们也提出了一些有用的方法,可以增进杂交细胞的生成及其富集。现在,这些技术的发展使得我们可以得到一种全新的细胞培养方法来进行人类基因作图。 英文
杂交细胞的培养
将亲代细胞混合并共同培养,用以形成杂交细胞。我们可以利用失活的仙台病毒[5,6]或者溶血卵磷脂[7]处理混合细胞,来促进细胞膜的融合。两种不同起源的亲代细胞融合后会产生一种双核的异核体。这些异核体的期望寿命很短,在接下来的第一次有丝... | 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 | 无论亲本细胞群的起源如何,在啮齿目动物–人类杂交细胞中,人类染色体更容易缺失是普遍的情况,研究者只报道了一个可能的例外[15]。汉德梅克提出了一种缺失机制(个人交流),即人类染色体不能有效地附着在杂交后代的纺锤体上,所以才会有较高的缺失发生率。另外一种并不与之相矛盾的可能性是一种分离机制,它基于小鼠和人类染色体的随机不分离以及含有部分人类细胞核型的杂交细胞的偏好性选择[16]。纳布霍尔茨等人[17]认为染色体的缺失是通过临时的两个不同的过程完成的。早期的缺失可能发生在细胞融合后的最先几次有丝分裂过程中,可引起几条或多条人类染色体的突然缺失。后来的缺失经确定是缓慢的逐步缺失,在某些情况下可持续多代细胞。纳布霍尔茨等人[17]也已给出证... | 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 | 通常这样的检测需要计算机来进行分析,因为所涉及的克隆体和遗传标记数量庞大。 英文
我们可以对每个克隆体的人类染色体进行列表并将它们与酶标记相联系,以此将单个基因或者同线性基因定位到特定的染色体中。染色体和酶表型同时存在或者缺失为控制将某一特定表型的基因定位到特定染色体中提供了证据。通过喹吖因显带、吉姆萨显带或者组成型异染色质染色技术,我们对每个克隆体的20~30个有丝分裂中期的染色体组型进行了分析。如果先用喹吖因对细胞进行荧光成像,然后再使用组成型异染色质染色技术,识别效果会增强。 英文
通过将一个克隆体中某一特定的染色体频率与指定表型的表达强度联系起来,往往可以强化该基因在特定染色体上的定位。然而,克隆体可以产生两种类型的差异克隆... | 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 | 也有证据表明四聚体型吲哚苯酚氧化酶B(IPO-B)和MOD之间存在同线性的关系(蒂施菲尔德、克里根和拉德尔,未发表)。 英文
麦克莫里斯等人[37]利用小鼠–人类杂交细胞将甘露糖磷酸异构酶(MPI)基因定位到7号染色体上。肖[38]报道了MPI和丙酮酸激酶3(PK3)的白细胞型之间存在同线性关系。 英文
没有基因定位于8号或9号染色体上。来自小鼠–人类杂交细胞的证据显示与细胞质型相关的谷氨酸–草酰乙酸转氨酶(GOT)基因可被定位到10号染色体上(克里根、蒂施菲尔德、麦克莫里斯、赫胥、陈和拉德尔,未发表)。 英文
布恩等人[29]利用小鼠–人类杂交细胞将乳酸脱氢酶A(LDH-A)定位到11号染色体上。肖[39]利用小鼠–人类杂交细胞报... | 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
布恩等人[29]利用小鼠–人类细胞的杂交后代报道了细胞质异柠檬酸脱氢酶(IDH)、细胞质马来酸氧化还原酶(MOR)和20号染色体之间存在着弱关联。现在,来自小鼠–人类细胞杂交后代的更广泛的数据表明IDH和MOR基因是不能够被定位到20号染色体上的。我们利用小鼠–人类杂交细胞得到了组织特异性的腺苷脱氨酶(ADA)基因位于20号染色体上的证据(蒂施菲尔德、克里根和拉德尔,未发表)。ADA与IDH和MOR之间均是非同线性的。体细胞家族的研究证明人类白细胞抗原葡糖磷酸变位酶3、P血型和ADA之间存在着连锁关系[56]。 英文
对于21号染色体,谭等人[57]利用体细胞杂交证明了二聚体型吲哚苯酚氧化酶A、(IPO-A)和一种遗传因子(精... | 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
(刘振明 翻译;梁前进 审稿)
Non-equilibrium Isotopic Fractionation between Seawater and Planktonic Foraminiferal Tests
N. J. Shackleton et al.
Editor’s Note
Harold Urey suggested in 1947 that, because the differential uptake of the two stable isotope of oxygen (16O and 18O) by marine microorganisms that form calcium carbonate ... | 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 | Until recently it has been assumed that this is also true of the Foraminifera. Support for this assumption comes from the seemingly reasonable temperature values which Emiliani4,5 derived making this assumption. Indeed, whereas the first work on molluscs was performed with the intention of investigating the isotopic fr... | 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 | plankton tows made in the Indian Ocean by US Coastal and Geodetic Survey Ship Oceanographer in 1967. The stations from which we have used samples in this study are given below in Table 1. Some samples are shown in Fig. 1. 中文
Fig. 1. Electron scanning micrographs of planktonic foraminifera from a 50 m horizontal tow (1... | 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 | Between species variation proves to be highly significant (P<0.001). The Students T test was used to test variation between species (Table 3). 中文
Table 3. Variation Between Species
中文
The residual variation is 0.1‰, which may be compared with the standard deviation of ±0.11‰ derived from the pairs of analyses. The ap... | 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 | Hecht and Savin12 have gone further, and attempt to use isotopic determinations to discover whether morphological variation within a population of foraminifera is due to varying ecological stress; they deduce, for example, that specimens of Globigerinoides ruber with a diminutive final chamber are those which have live... | 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 | station 15. Using these estimates and the relation between temperature and isotopic composition given by Craig17 yields the values in Table 4. Comparison with the measured isotopic composition for each species from Table 2 gives the extent of departure from isotopic equilibrium for each species. The estimates range fro... | 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 in any case not possible to use the data to correct measurements made in other laboratories because at present results from different laboratories do not seem to be related to each other. For example, specimens of Globigerinoides sacculifera from the top of core P6304-8 gave –1.29‰ when analysed by Emiliani6; sam... | 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 | Emiliani, C., Amer. J. Sci., 252, 149 (1954).
Duplessy, J. C., Lalou, C., and Vinot, A. C., Science, 168, 250 (1970).
Van Donk, J., thesis, Columbia Univ. (1970).
Shackleton, N. J., J. Sci. Instrum., 42, 689 (1965).
Urey, H. C., Lowenstam, H. A., Epstein, S., and McKinney, C. R., Bull. Geol. Soc. Amer., 62, 399 (1951).... | 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
到目前为止,除了范当柯分析的一些样品外,所有已发表的针对浮游有孔虫氧同位素分析使用的材料均是化石或亚化石。这是因为在通常情况下,采用拖网的方法采集浮游有孔虫很难得到足够大的样本容量,因而不能满足常规同位素分析的要求。目前,我们已经能够对只有0.04 mg碳酸盐的小样本进行分析,并且用到美国海岸与陆地考察船“海洋学家”号在1967年制作的一系列印度洋拖网浮游样本。表1列出了本研究中样本的采集站位信息,图1显示了一些样本的相关信息。 英文
图1. 50 m水平拖网(南纬16°38′,东经113°03′)采集到的浮游有孔虫的电镜扫描图。a,G. ruber (×65)(红拟抱球虫);b,G. sacculifera (×65)(袋... | 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 | 而站位3、4和5的盐度似乎略高一些,相应的PDB标准下测定的同位素组成为+0.1‰。关于温度方面,站位3、4、5、6和7的八月份平均表层水温(德凡特[16],图版3B)都是27°C,而站位15的八月份平均表层水温则为25°C。利用这些估算值以及克雷格[17]给出的温度和同位素组成之间的关系得到了表4中的一系列数值。通过与表2中列出的各物种的同位素组成相比较,可以得出不同物种偏离同位素平衡的区间。估算值从G. ruber的–0.50‰到P. obliquiloculata的+0.06‰之间不等。 英文
表4. 据同位素平衡估计的偏差
英文
表4中,第4列显示了在第2列的温度下沉积的碳酸盐的同位素组成;而第3列显示的水的同位素组成是... | 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 | known now as magnetic resonance imaging (MRI), is used ubiquitously in basic and applied science, especially medicine. In 2003 Lauterbur shared a Nobel Prize with Peter Mansfield, who developed methods for analysing MRI signals. 中文
AN image of an object may be defined as a graphical representation of the spatial distri... | 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 | coil, the signal in the presence of a field gradient represents a one-dimensional projection of the H2O content of the object, integrated over planes perpendicular to the gradient direction, as a function of the gradient coordinate (Fig. 1). One method of constructing a two-dimensional projected image of the object, as... | 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. Proton nuclear magnetic resonance zeugmatogram of the object described in the text, using four relative orientations of object and gradients as diagrammed in Fig. 1.
中文
Fig. 3. Proton nuclear magnetic resonance zeugmatograms of an object containing regions with different relaxation times. a, Low power; b, hi... | 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 | ease with which field gradients large enough to shift the narrow resonances by many line widths may be generated, NMR zeugmatography of solids, electron spin resonance zeugmatography, and analogous experiments in other regions of the spectrum should also be possible. Zeugmatographic techniques should find many useful 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 | 假定发射—接收线圈区域内的信号强度均匀,在施加梯度场后获得的信号代表了实验样品中水含量分布沿梯度垂直方向的一维投影,它是与梯度坐标相关的函数(如图1所示)。绕垂直于梯度场方向的轴转动实验样品(或如图1所示,以样品为轴转动梯度场),获得实验样品的一系列一维投影。以此为基础,采用投影重建的方法[1-5]可构建出表示实验样品水含量分布的二维投影像。利用如图1所示的四个不同方向的一维投影并采用类似于戈登和赫尔曼的投影重建算法[4],可以构建出如图2所示的20×20的图像矩阵,此图像是由矩阵点间轮廓线插值的描影法来显示,它清楚地表征了这两组圆柱体水的位置和大小。在第二个实验中,一根毛细管内装的是纯水,另一根毛细管中装的是0.19 mM浓度的M... | 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 | potential treatment for type I diabetes mellitus, where the immune system destroys insulin-producing beta cells in the islets of Langerhans. Successful transplants have reduced or removed the need for insulin therapy. 中文
PANCREATIC transplantation with the aim of treating diabetes mellitus has so far met with little su... | 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 | Initially, albino outbred rats and subsequently young adult inbred hooded rats (strain PVG/C) were used. Following killing by cervical dislocation, the ventral surface of the animal was shaved, prepared with chlorhexidine in spirit and the abdomen opened with a midline incision. Using a dissecting microscope, magnifica... | 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 | Initially the view was obscured by fine fragments of acinar tissue, which were removed by gently agitating the Petri dish and allowing them to become suspended in the Hanks’ solution, then aspirated and discarded, the Islets remaining on the bottom of the vessel. They could then be seen clearly (Fig. 1) by the aid of 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 | We have now established a successful method of isolation of Islets of Langerhans in an animal strain in which inbred immunologically isogeneic lines are available, making possible transplantation studies uncomplicated by rejection problems. These cells can be grafted and survive for appreciable periods of time as 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 | 此后,莫斯卡勒夫斯基[4]描述了一种胶原酶消化法,该法已经在兔子中取得成功,而且分离出的胰岛数量也得到提高,后来莱西和科斯蒂安诺夫斯基[5]在大鼠中对这个方法进行了改进。但是,即便使用了诸如区带离心和密度梯度离心的分离方法,仍然很难获得游离的胰岛,而且这些细胞的生存能力也是一个大问题。 英文
我们建立了一种方法,并用此法从大鼠胰腺中稳定制备了大量用于移植的胰岛,并且通过移植确认了细胞的生存能力。 英文
起初使用的是白化的远交系大鼠,后来使用年轻成年的头部有斑点的顶罩大鼠(PVG/C系)的近交系。颈椎脱臼法处死大鼠后,刮除腹面毛发,用溶于酒精的氯己定处理后选取正中线切口开腹。使用解剖显微镜放大10倍,将一条细小的聚乙烯导管(“Intr... | 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 Earth’s lower mantle is inaccessible for direct study. The best method for probing it is through the measurement of seismic waves, which travel at different speeds through materials of different density or composition. Although there were some earlier signs that the lower mantle is not uniform but somehow “lumpy”, ... | 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 | anomalies are represented as vectors in slowness space. Many anomalies are found which are too large to be effects of upper mantle heterogeneities in the source regions; on the other hand, the anomalies often vary rapidly with the direction of approach of the waves, implying that structure directly beneath the array is... | 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 travel time curve thus determined is shown in Fig. 1 (in terms of deviation from the standard Jeffreys-Bullen tables), together with the data means and their standard errors for 2°distance intervals. This curve is similar in shape to those found in other recent studies7,8 except beyond 85°, where most other curves ... | 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 | locations in each region are typically distributed over >200 km. Velocity variations near the focus are further ruled out because early arrivals beyond 85° are not restricted to observations of deep earthquakes; they also occur, for example, in data from nuclear explosions in the Marshall Islands9. 中文
Fig. 1. P wave 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 | showed significant variations from the average curve, whereas for smaller distances, only 3 anomalous paths (out of 22) were found. This strongly suggests that most of the scatter originates in the deep mantle (depth >2,000 km). The possibility of the variations occurring at a shallower depth cannot be absolutely dispr... | 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 actual details of the velocity distribution cannot, however, be determined precisely, because rays travel a great distance at approximately the same depth near their turning points. Fig. 4 shows the regions of the lower mantle sampled by the various ray bundles (defined arbitrarily as the central 30°of each path) 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 | The mean travel times in Table 1 show a variation of about 1.5 s for rays bottoming below 2,600 km, and about 0.6 s for rays bottoming between 2,000 and 2,600 km. These numbers are somewhat uncertain, but it is likely that the true travel times vary by at least 1 s. The amount by which the actual velocity in the mantle... | 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 | proposed plume regions can be obtained, they may provide valuable evidence relevant to the Wilson-Morgan hypothesis. 中文
Except, perhaps, for the Hawaiian Islands, no geological or tectonic features show an obvious correlation with the inferred deep mantle velocity anomalies. At shallower depths, however, this is not th... | 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 | Bruce R. Julian and Mrinal K. Sengupta
Lincoln Laboratory, Massachusetts Institute of Technology, Lexington, Massachusetts 02173
Received January 2, 1973.
References:
Toksöz, M. Nafi, Chinnery, M. A., and Anderson, D. L., Geophys. J. Roy. Astron. Soc., 13, 31(1967).
Hales, A. L., and Roberts, J. L., Bull, Seismol. So... | 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 | 所涉及的18个地震带中,大多都有两次或两次以上的地震数据是可用的。另外,为了消除含有过失误差的数据,每个台站的资料都进行了一致性检验。利用一种类似于赫林等人[7]所描述的迭代法,我们确定了地震位置、一条震源深度为550 km的地震波走时曲线和一组“台站校正量”(每个台站对应一个常数),每个常数代表走时在该台站下方上地幔的横向变化造成的影响。 英文
由此得出的走时曲线如图1所示(以相对于标准的杰弗里斯-布伦走时表的偏差表示),图中也显示了间距为2°的数据的平均值及其标准误差。在85°以下,曲线的形状与近期其他研究发表的曲线[7,8]相似,大部分其他曲线仍然与杰弗里斯-布伦曲线近似平行,但我们的结果逐渐提前了约0.9 s。图2显示了绘制... | 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 | 这些区域往往都是真正可能出现速度异常的区域。图中一些区域重叠的地方,它们的数据也基本保持一致(例如区域1-6和1-7、2-2和2-3、4-1和4-6)。这种一致性是令人鼓舞的,因为这支持了我们的观点,即走时的异常产生于深地幔,而不是由某种系统误差所引起的。在区域1-3和1-16之间存在着显著的不一致性,但是这并不奇怪,因为走时异常实际源于何处并不确定。沿着路径1-3传播的射线穿过了区域2-2和2-3后继续向北,很可能走时异常就产生于此。图4还有一个有趣的特征,即在两个距离间隔最大的异常之间存在相关性(例如区域1-7和2-7、区域1-4和2-4、以及区域1-5和2-6),这表明深地幔的结构在垂直方向上至少在几百公里内具有一种空间“一致... | 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
(张效良 翻译;张忠杰 审稿)
Evidence for an Advanced Plio-Pleistocene Hominid from East Rudolf, Kenya
R. E. F. Leakey
Editor’s Note
Richard Leakey followed his father Louis’ vocation in palaeontology at first very reluctantly, but soon began to make remarkable discoveries of his own. This one, from the eastern shore of Lake Ru... | 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 | Area 131 consists of approximately 30 km2 of fluviatile and lacustrine sediments. The sediments are well exposed and show no evidence of significant tectonic disturbance; there is a slight westward dip of less than 3°. Several prominent marker horizons provide reference levels and have permitted physical correlation 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 | Detailed palaeomagnetic investigation of the sedimentary units is being undertaken by Dr. A. Brock (University of Nairobi). Systematic sampling closely spaced in the section has identified both the Mammoth and Kaena events in area 105 between the Tulu-Bor and KBS Tuffs, a result which supports the 2.61 m.y. date on the... | 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 | Cranium KNM-ER 1470 was discovered by Mr. Bernard Ngeneo, a Kenyan, who noticed a large number of bone fragments washing down a steep slope on one side of a gully. Careful examination showed that these fragments included pieces of a hominid cranium. An area of approximately 20 m×20 m was subsequently screened and more ... | 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. Cranium KNM-ER 1470. a, Facial aspect; b, lateral aspect; c, posterior aspect; d, superior aspect.
中文
The palate is shallow, broad and short with a nearly straight labial border that is reminiscent of the large Australopithecus. The great width in relationship to the length of the palate does contrast markedl... | 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 | compared with a restricted sample of modern African bones, there are marked similarities in those morphological features that are widely considered characteristic of modern H. sapiens. The fragments of tibia and fibula also resemble H. sapiens and no features call for specific comment at this preliminary stage of study... | 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 | genus. This seems unacceptable and also other morphological considerations argue strongly against such an attribution. 中文
The Olduvai Gorge has produced evidence of an hominine, H. habilis; the estimated endocranial volumes for three specimens referred to this species are 633, 652 and 684 cm3 (ref. 10). The Olduvai 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 | gratefully acknowledged. 中文
(242, 447-450; 1973)
R. E. F. Leakey
National Museums of Kenya, PO Box 40658, Nairobi
Received January 23, 1973.
References:
Leakey, R. E. F., Nature, 242, 170 (1973).
Leakey, R. E. F., Nature, 231, 241 (1971).
Leakey, R. E. F., Nature, 237, 264 (1972).
Leakey, R. E. F., Mungai, J. M., and... | 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 | 这些凝灰岩已经在108区和105区被定位(见图1),K/Ar年代测定的样品就是在这两个区采集的。冯德拉和鲍恩已经对该处的地质情况进行了说明[7]。图2给出了垂直方向上这四个人科动物标本的位置与KBS凝灰岩关系的剖面示意图。 英文
目前,由于透长石存在明显的变化,所以对从131区的KBS凝灰岩层采集到的样品进行的年代测定分析结果已不具有决定性。但这种现象并未在105/108区同一层位采集到的被确定为261万年前的样品中出现,因此,没有理由怀疑261万年这一年代的真实性(来自与米勒的个人交流)。 英文
图2. 此图显示了131区沉积物的地层序列以及人科动物化石KNM-ER 1470、1472、1475和1481与KBS凝灰岩在垂直方向... | 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
相关联的骨骼KNM-ER 1481
哈里斯博士还发现了一根完整的左侧股骨KNM-ER1481,这根股骨与同时发现的左侧胫骨两端以及左侧腓骨远端相关联。 英文
该股骨(见图4)的特征是具有很细长的骨体以及相对较大的骨骺。股骨头部大,长在一个粗壮的从骨体生出的圆柱状颈上,该颈部与骨体形成的钝角比已知的南方古猿股骨的要大。臀大肌有一个明显的插入,骨体的近端区域在前后方向上有些扁平。股骨髁突与股骨的角度属于智人的范畴。当把该股骨与一个特定的现代非洲骨骼标本进行比较时,普遍认为它们在形态学特征上与现代智人的特点有显著相似性。胫骨和腓骨破片也与智人相似,就目前的初步研究阶段来看,还没有需要特别讨论的特征。 英文
图4. 左侧股骨KNM-... | 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 | effectively as drug analgesia, and only really works well in upper-body operations such as thyroidectomies and lung surgery. Given this, the duo suggests that acupuncture analgesia sometimes be considered an alternative but not a replacement to drug therapy. 中文
Acupuncture analgesia can sometimes be considered as an al... | 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 present in China this technique is widely used in both urban and rural hospitals and in mobile medical clinics. It has been used for surgery on the brain, neck, chest, abdomen and limbs. In addition, it has been applied in obstetric operations and in operations on the ears, nose and throat. Acupuncture has attained ... | 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 | To illustrate the use of this technique in surgery, we shall describe its application in a thyroidectomy, where the best results have been obtained. Two preliminary steps are necessary. First, the consent of the patient must be obtained. In addition to explaining the procedures to him, it is highly recommended that a 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 | Acupuncture analgesia does not completely remove pain. For this reason, electric cauterization must not be used to stop bleeding. Instead, either ligation or pressure must be used. In addition, the patient must be warned that some uncomfortable feeling may be caused when the muscle is pulled around the neck and thyroid... | 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 are few physiological reactions, the patient recovers his normal physical and mental state very quickly. In addition, the patient is more psychologically fit after an operation using acupuncture analgesia. According to our observations, the patient has been aware of and understood the entire surgical process as h... | 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 | Second, the surgical cases must be selected carefully. When choosing a patient to undergo surgery with acupuncture analgesia, his illness must be considered. For example, in operations such as gastrectomies for gastric ulcers and pyloric stenosis, only if the operating time is short is it appropriate to use acupuncture... | 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 | Acupuncture analgesia does not dull the nerves as completely and effectively as drugs. Thus, it is not suitable for every operation. On some occasions when the first incision is made, when suturing commences and/or when the procedure is long, the pain threshold may be decreased so as to render the analgesic effect rela... | 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 | importance of this development must not be neglected. 中文
(242, 559-560; 1973)
S. B. Cheng and L. K. Ding
Chinese Medical Research Centre, 566-568 Nathan Road, Kowloon, Hong Kong
针刺镇痛的实际应用
郑,丁
编者按
在这个时期,针刺镇痛在中国的广泛应用吸引了西方的关注。本文中中医师郑和丁总结了在手术中使用这项技术的利弊。这种技术与麻醉剂相比成本更低廉,带来的并发症更少,在有信心的患者身上发挥了特别好的功效。但是它并不像麻醉剂那样有效地使神经麻木,而且实际上只... | 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 | 这里我们只讨论三点。首先,正如我们所提过的,针刺镇痛在保持患者意识的情况下可以使神经麻木,这不同于麻醉剂麻醉。这样便于医生和患者间的合作。再以甲状腺切除术为例,医生能够随时与患者交谈,而通过听患者的声音就能够判断是否损伤了喉返神经。另一个例子就是心肺手术。在打开切口之后,医生能够指导患者进行深度的腹式呼吸以防止胸腔纵膈膜突然摆动。同时还能保持肺处于膨胀状态,这就不会干扰手术以及患者的呼吸。 英文
其次,与使用麻醉剂相比,针刺镇痛的生理和心理并发症更少。利用针刺镇痛手术时,我们发现血压、脉搏和呼吸仍然保持平稳。这通常在药物麻醉时不容易实现。利用针刺镇痛进行手术后,不会出现药物麻醉所导致的副作用或者并发症。此外,由于出现的生理反应较少,... | 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
(毛晨晖 翻译;于天源 审稿)
Experiments on Polishing of Diamond
J. Wilks
Editor’s Note
The interest of this contribution from John Wilks at Oxford is not so much in the specific findings—that polished diamond is microscopically rough—but in the way it touches on several themes in materials science that have become increasingly... | 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 | material during polishing with a bonded wheel in a direction parallel to a cube axis is about 100 times greater than if the same face is polished in a direction at 45° to a cube axis. Similar effects are observed on other faces, and even greater differences are evident when polishing on a cast-iron scaife, as the more ... | 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 view of all this, one would expect to encounter difficulties both in removing material from diamonds and in polishing them. As far as the removal of material is concerned, there is no harder substance than diamond which can be used to produce abrasive cutting. In rubbing operations, the high thermal conductivity 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 | treatment was criticized on the grounds that diamond is certainly not built up of equally sized elementary blocks as in his model, but the essential function of the model is to indicate the positions of the cleavage planes—and this it does correctly. It now turns out, as the result of various experiments on diamond ove... | 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 | always occurs by plastic deformation rather than cleavage. On the other hand, the calculations show that, of the substances considered, sodium chloride and diamond are most likely to fail by brittle fracture. The critical stresses for shear and cleavage in sodium chloride and diamond are approximately equal, but the ca... | 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 sometimes suggested that plastic flow in diamond may be produced by conditions of intense local pressure. The effect of pressure on brittle materials is sometimes surprising, for example it is possible to compress a slab of brittle material, such as rock salt, to half its initial thickness without producing crack... | 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. Scanning electron microscope micrograph of a diamond surface indented with a Knoop indenter (×8,400).
中文
We shall now describe three sets of experiments which confirm the fracture process and illustrates the unusual properties of polished diamond surfaces. In the first set a simple micro-abrasion tester21 was... | 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 diamond surface which has been polished by a process of mechanical chipping will not be atomatically flat but must consist of hills and valleys bounded by an irregular arrangement of cleavage planes as shown very schematically in Fig. 3A. It follows that abrasion proceeds by the removal of material from the tops or s... | 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 have also made studies of the jagged nature of polished diamond surfaces, implied by our abrasion experiments, by observing the friction of diamond sliding on diamond in air. Some time ago Seal7 showed that the friction of a polished cube surface varies with the azimuthal angle of sliding, with a four-fold symmetry.... | 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 | to be abrupt and irreversible. The work of separation is proportional to the load, so this type of mechanism leads to a value of the friction which is independent of the load. We believe that this mechanism accounts quite generally for the friction of diamond on diamond in air as discussed in more detail by Casey and W... | 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 | present a jagged surface with a four-fold symmetry. If, however, the diamond is polished in one of the hard directions, the surface structure will tend to take the form of grooving parallel to the direction of polish, with the two-fold symmetry shown in the friction measurements. We are at present extending our studies... | 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 are features lying in these directions. Further details of our results, together with details of the replication technique, will be published elsewhere. 中文
Diamond is perhaps unique in that an apparently highly polished surface may in fact be mechanically rough on a microscopic scale, a result which is the conseq... | 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 | Wilks, E. M., J. Opt. Soc. Amer., 2, 84 (1953).
Tolkowsky, M., thesis, Univ. London (1920).
Wilks, E. M., and Wilks, J., J. Phys. D., 5, 1902 (1972).
Wilks, E. M., and Wilks, J., Phil. Mag., 38, 158 (1959).
Seal, M., Proc. Roy. Soc., A248, 379 (1958).
Kelly, A., Strong Solids (Clarendon, 1966).
Kelly, A., Tyson, W. R.,... | 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
抛光的金刚石表面具有不同寻常的性质,因为这种脆性物质的抛光通常是通过机械切削来进行的。 英文
在过去的几百年中,将金刚石加工成形和抛光以生产宝石所用的方法在本质上保持不变。一直到最近,这些操作的物理学基础才得到了研究,它们那不同寻常的特征也得到了充分的理解。本文概述了抛光过程的主要特征,并且描述了一些最近的实验,它们阐明了对于抛光过程本身和所产生的抛光表面都极有特征性的本性。我们将要说明,这些独特性质可能是由金刚石极硬且脆的本性所导致的。 英文
抛光金刚石的常规方法是将金刚石抵在覆盖着细小金刚石粉末的轻油悬浊液的旋转铸铁轮(或磨光盘)表面上,或者是抵在表面嵌入金刚石粉末的金属基体的轮表面上。这种方法一个最令人吃惊的特征是,如果... | 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 | 他们指出,对于诸如铜、金和银等面心金属来说,产生断裂所需的应力是产生切变所需应力的约30倍,而且破坏的产生经常是由于塑性形变而不是解理。另一方面,计算表明,在所考虑的各种物质中,氯化钠和金刚石是最容易由于脆性断裂而破坏的。氯化钠与金刚石中切变和解理的临界应力是近似相等的,但是计算还没有精细到足以指出哪一过程是更为有利的。不过,这些计算都是针对理想晶体的,而对于真实材料的实质问题是,位错的存在和运动是否会允许先塑性流动后再断裂。 英文
金刚石中的位错已被埃文斯[10]所观测到,他用蚀刻法制备金刚石样品,然后在透射电子显微镜下直接观察到了位错。弗兰克和兰[11]也用X射线照相技术对其进行了清晰的描述。埃文斯[12]所提到的计算指出位错的... | 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 | 从形貌的角度看,磨削轮一定会得到数量增加的b类型的边,而硬度则相应地下降。类似地,相反方向上的偏离则会增加硬度。 英文
图3. 抛光后金刚石表面的示意图(见正文)。
英文
我们还可以预期硬度随偏离的变化会非常快。如果微小山峰的线性尺度全都具有同样的数量级h,与磨削轮接触的山峰之间的平均距离就会大很多,因为真正的接触面积不到名义上的面积的10–4。因此山峰之间的距离可能具有100h的数量级,才能使1°的偏离就足以使图3A中的形貌改变成图3B中那样,并由此而使易磨削位置的数目近似翻了一倍。类似的论证可以用来解释正的与倾斜的立方体面和十二面体面的硬度。从这个模型所能得到的所有预言都与实验结果吻合[5]。 英文
我们还对磨削实验显示的... | 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 | 这些结果确认了一个为金刚石抛光者所熟悉的事实,即抛光的质量取决于所抛光的特定的面,如同从抛光过程的机械性质中所得知的那样。人们期望至少在某种程度上表面结构可以用解理面来加以描述。在一个立方体表面上,这些解理面的交线会位于与抛光方向成45°角的方向,而且值得注意的是,在这些方向上存在着形貌特征。关于我们的结果的更多具体内容以及制样技术的细节,将会在其他文章中发表。 英文
金刚石的独特在于它外观上高度抛光的表面可能实际上在显微镜尺度下却是机械粗糙的,这是其脆性所导致的后果。由于金刚石的磨损速率和金属表面的光亮效果都高度依赖于工具的表面结构,因此目前我们正在将这些结果运用在将金刚石制成金属加工的切割工具上。例如,两个具有相同外部几何形状但... | 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 | sea level arising from changes in the form of the ocean basins are revealed in the geological record on continents as longer period (~107 yr) transgressions and regressions that mark global changes in sea level4,5, although the magnitude of the change may vary locally. Five principal factors1,3,6 control sea level; 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 | analysis (Fig. la) because constancy of water volume and rock density require that the total area representing crust and water volume must remain constant. To study a systematic series of deviations from the present curve, we varied the continent area (x) and maximum ocean depth (y) independently in 5% increments on ei... | 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 | isostatic grounds and because uplift is unlikely to exceed erosion by a sufficient amount. 中文
Typical hypsographic curves for two extreme conditions are shown in Fig. 1. For each of the generated curves, the ocean area was drawn in with constant ocean volume and the sea level derived to an accuracy limited by scale to ... | 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 oceanic part of a plate steadily subsides as it spreads away from the mid-ocean ridge axis3,19,20 and the aseismic continental margin undergoes a similar thermal subsidence that declines exponentially with a time constant of about 50×106 yr (ref. 21). Transgressions and regressions on young margins may be masked 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 | between 55 and 60 m.y. and about 70 m.y. Comparison of the ages of these discontinuities and eustatic changes documented on continental margins (Fig. 4 and Fig. 5) shows (within the limitations of the data) that the Oligocene-Miocene spreading deceleration is associated with a regression preceded by a minor transgressi... | 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 | uplifted to near its present elevation just before the 10 m.y. acceleration. Although these elevation changes correlate well with eustatic changes, the differences between the observed data and empirical model suggest that, at the slow (1.12 to 1.74 cm yr–1) spreading rates on this ridge18, effects such as phase change... | 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 | example, have contributed to the drying out of the Mediterranean in the Miocene37 (see Fig. 2). 中文
We thank H. Charnock and A. S. Laughton for their comments on the manuscript. Peter Hunter drew the diagrams. 中文
(243, 19-22; 1973)
N. C. Flemming and D. G. Roberts
National Institute of Oceanography, Godalming, Surrey
Re... | 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 | Pitman, W., and Talwani, M., Geol. Soc. Amer. Bull., 83, 619 (1972).
Le Pichon, X., J. Geophys. Res., 73, 3661 (1968).
Vogt, P., et al., Tectonophysics, 8, 285 (1969).
Schneider, E., and Vogt, P., Nature, 217, 1212 (1968).
Ewing, M., and Ewing, J., Science, 156, 1590 (1967).
Menard, H. W., Science, 157, 923 (1967).
Max... | 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 | 本文中,英国海洋科学研究所的两位科学家提出大陆漂移可能会使海平面发生很大程度变化的问题。开展此项研究的原理为,地球表面倾向于保持“均衡”平衡。这意味着对深部流体地幔所施加的压力在各处是相同的,换句话说,大陆之所以能够存在仅仅是因为它们的密度低于构成大洋海床的岩石密度。 英文
本文阐述了一个估计全球海平面变化的模型以及海平面变化与海底扩张之间具有相关性的证据。 英文
全球海平面变化是由地壳形态或大洋水总体积的变化引起的[1]。后者的最好例子就是第四纪冰川进退所产生的短期(约105年)可逆的变化,尽管中生代和新生代时期地幔的去气也可能使大洋水体积增加[2,3]。在大陆的地质记录中,标志全球海平面变化的更长时期(约107年)的海进和海退可... | 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 | 英文
变化和不连续性
当一个板块的大洋部分由洋中脊向外扩散的时候,它会稳定沉降[3,19,20]。无震大陆边缘也会经历类似的热沉降,并且在大约50×106年的时间内其沉降速率呈指数减缓(参考文献21)。海进和海退过程在年轻大陆边缘上会被此种效应所掩盖,因此在老于5,000万年的大陆边缘上才较有可能观察到。斯利普建立了古老三叠纪[22]美国大西洋边缘广义的沉降曲线[21],我们对其所显示的海进和海退进行了研究,并将其与独立获得的北大西洋扩张史[23,24]中的事件进行了对比(图3)。比较结果显示,渐新世的海退与4,500万年前洋中脊扩张速度的减慢有很好的对应关系。更早期的海平面变化与洋中脊扩张的不连续性之间也具有相关性。 英文
图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 | 这种规模的海平面下降可以使半封闭海的海槛暴露,使其环流发生变化,并且可能导致海水完全蒸发。例如,这样规模的海平面下降可能是中新世地中海干枯的原因[37](参见图2)。 英文
我们感谢查诺克和劳顿对手稿的讨论,彼得·亨特为本文绘制了图表。 英文
(李任伟 翻译;孟庆任 审稿)
Resonance Raman Spectroscopy of the Photoreceptor-like Pigment of Halobacterium halobium
R. Mendelsohn
Editor’s Note
The purple membrane of the salt-loving photosynthetic bacterium ... | 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 potentially useful area of application for this technique is to photoreceptor pigments. The bathochromic shifts in visual pigments have not yet been satisfactorily explained. The absorption maxima of these pigments, in which there appears to be a Schiff base of 11-cis retinal with the ε-amino group of a lysine resi... | 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 | shift from λmax=558 nm to λmax=570 nm on exposure to red or blue light respectively14. (c) The membrane is easily handled at room temperature in aqueous suspension. 中文
The purple membrane used in the study described here was the gift of Drs D. Oesterhelt and A. E. Blaurock. 中文
Cells of Halobacterium halobium were grown... | 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 | Several experiments showed that the observed spectra were resonance-enhanced. (a) The protein concentration as measured from the visible spectrum (εmax=54,000 l/mol cm)14 was 5.5×10–5 M or two orders of magnitude less than that required to obtain ordinary protein Raman spectra15. (b) On bleaching the pigment with 0.1 M... | 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. Excitation profile results. ---, Ratio of the integrated intensities of 1,568 cm–1 vibration compared with 983 cm–1 vibration of ion used as internal standard. ..., Same ratio comparing the 1,531 cm–1 vibration with the standard. ■ and ●, Experimental points, observed at the indicated laser wavelength. Error ba... | 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 Fig. 3a and c, the 1,500-1,700 cm–1 region of the Raman spectra of unprotonated and protonated retinylhexylamine are shown. The C=N frequencies in this model Schiff base are expected to be similar to those of the pigment Schiff base and can be used to decide whether the nitrogen of the latter is protonated. In the u... | 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 | cm–1 band disappears as expected, while the vibration near 1,623 cm–1 becomes more prominent (Fig. 3d) than in the H2O preparation. This band, assigned to C=N stretch of the Schiff base, appears at the same frequency as in unprotonated retinylhexylamine and strongly suggests that the Schiff base in the pigment itself i... | 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 | frequencies upon complex formation. In addition λmax in such complexes are quite solvent dependent16, as observed in the present case. That such a mechanism is feasible has been shown by Ishigami et al.17, who observed charge transfer between tryptophan and 9-cis retinal in acidified methanol solution (λmax of complex=... | 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 | Behringer, J., in Raman Spectroscopy (edit. by Szymanski, H. A.) (Plenum Press, New York, 1967).
Dartnall, H. J. A., and Lythgoe, J. N., Vision Res., 5, 81 (1964).
Hubbard, R., Nature, 221, 432 (1969).
Abrahamson, E. W., and Ostroy, S. E., Prog. Biophys. Mol. Biol., 17, 181 (1967).
Morton, R. A., and Pitt, G. A. J., Bi... | 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 | 每张谱图中,都有一个位于1,531 cm–1处的最强振动,以及其他约十五个可分辨出的峰。两张谱图中唯一的显著区别,就是位于1,568 cm–1处的振动与1,531 cm–1处的相比,其相对强度不同。用4880 Å的射线激发时,1,568 cm–1处的峰比用5145 Å的射线激发时强约四倍。下面将解释这一观测结果。 英文
图1. 使用“Spex”1401型拉曼光谱仪,得到紫膜碎片水悬浮液(紫色蛋白质浓度为5.5×10–5 M,pH 7.0,不含缓冲剂)的拉曼光谱图:(上图)100 mW Ar+激光产生的4880 Å射线。分辨率7 cm–1;时间常数2 s;扫描速率25 cm–1·min–1;光子计数检测;1 mm内径的毛细管池,横向... | 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
图3. 拉曼光谱图的1,500~1,700 cm–1区域,其中a,未质子化的视黄基己胺(浓度10–3 M的C6H14溶液,λmax =360 nm);b,紫膜碎片在水中的悬浮液(见图1的上图,图注);c,质子化的视黄基己胺(浓度10–4 M的酸化乙醇溶液,λmax = 445 nm);d,紫膜碎片在D2O中的悬浮液(除溶剂外,条件与图1的上图相同)。所有谱图都是在4880 Å光照射下记录的。在a和c之间的浓度差别反映出,共振增强在视黄基己胺的吸收带向可见光区域移动时变大。这种席夫碱在不同溶剂下其拉曼频率改变很少甚至没有变化。在已提到的溶剂中获得了未质子化和质子化的视黄基己胺的最佳谱图。
英文
图3b中所示为紫膜光谱的1,... | 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 | Does solar activity influence how fast the Earth spins? The idea sounds unlikely, but in 1959, following one of the largest solar storms in recorded history, Andre Danjon reported an apparent sharp increase in the length of the day as measured by astronomical means. Here John Gribbin and Stephen Plagemann tested this 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 | that event. Changes in the length of day, and thus in the spin rate of the Earth, are revealed by regular measurements of Universal Time (UT) carried out at many observatories around the world. For our purpose, we are interested in UT2, the version of Universal Time with the effects of the Chandler Wobble and seasonal ... | 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 effects are not so dramatic that one would necessarily attribute them to an outside cause on the basis of these data alone, but they take on a greater significance in the light of out prediction, following Danjon, that just such a change should occur soon after a great solar flare. We are confident that the effec... | 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 | Danjon, A., CR Acad. Sci. Paris, 254, 3058 (1962).
Danjon, A., Notes et Informations de l’Observatoire de Paris, 8, No. 7 (1962).
Schatzman, E., in The Earth-Moon System (edit. by Cameron, A. G. W., and Marsden, B. G.), 12 (Plenum, New York, 1966).
Pomerantz, M. A., and Duggal, S. P., Nature, 241, 331 (1973).
Chupp, E.... | 400套付费套装书 |
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