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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 | More stringent limits can be placed on this channel by recognizing that the tritium, emitted with kinetic energy of 1.0 MeV, can initiate the t(d, n)4He reaction. By integrating the energy-dependent reaction cross-section10 over the range of the tritium within the Pd, we obtain a d + t fusion probability of 4×10–5 per ... | 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 general search was also performed throughout the entire 0.1–25.5-MeV energy interval for possible γ-ray lines above background in each residual spectrum. Candidates were required to have at least one channel with counts in excess of 3σ (σ being the propagated Poisson error for that channel’s count) and a summed exces... | 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 maximum fitted election emission rate, 2.6×103 electrons per second, corresponds to a fusion power level of 10 nW. 中文
Neutron Detection with Nuclear Track Detectors
A significantly lower limit than the 10 pW discussed above on the mean neutron production rate during a 67-h interval (16–19 May) was obtained with neu... | 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 | Fission track counts for each sandwich’s pair of foils are shown in Fig. 1, the first number being the count for the foil without a Cd cover and the second being that with. There was no indication of an excess neutron signal from any of the cells; in fact, the control sandwich, adjacent to the water-tank wall, register... | 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 | Pons, personal communication), because this boiling event may very well have a conventional explanation. Unfortunately we have not received any numerical data on excess heat production during the 831 h of our monitoring, so we are not able to correlate the absence of nuclear signatures with the presence of anomalous he... | 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 | M. H. Salamon*, M. E. Wrenn†, H. E. Bergeson*, K. C. Crawford‡, W. H. Delaney*†, C. L. Henderson†‡, Y. Q. Li*, J. A. Rusho*, G. M. Sandquist‡ & S. M. Seltzer§
* Department of Physics, † Environmental Radiation and Toxicology Laboratory and ‡ Nuclear Engineering Department, University of Utah, Salt Lake City, Utah 84112... | 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 | Andersen, H. H. & Ziegler, J. F. Hydrogen Stopping Powers and Ranges in all Elements (Pergamon, New York, 1977).
Acknowledgements. We thank S. Pons, M. Anderson and M. Hawkins for their hospitality during our work in their laboratory. We thank K. Wolf for alerting us to the t(d, n)4He reaction that follows d(d, p)t, 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 | 电解池2-1,2-5和2-7的钯阴极直径/长度(以厘米为单位)分别为0.4/1.25、0.4/10.0和0.1/10.0;电解池2-3有尺寸为0.1/10.0的铂阴极。俯视图中每一个三明治结构显示的两个数字(n,m)分别是没有镉覆盖层和有镉覆盖层的铀箔塑料薄膜中记录的裂变碎片数目。只分析每个箔中的一个塑料薄膜。 英文
γ射线的NaI探测
让四个开放的电解池(不进行气体收集)近乎连续地进行电解,同时NaI探测器在收集数据(5月9日至6月16日)。这些电解池由D2O(0.1 M LiOD)电解质和铂阳极构成;阴极如图1所示。电解池在恒电流模式下运行,电流设定值在五周内是变动的。 英文
NaI探测器系统被放置于支撑水槽和电解池的桌子下方... | 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 | 在这个分布(以及后面其他的分布)中我们排除了两个图谱,因为它们含有来自22Na和137Cs源的光电峰,这是由于其他人将这两种放射源带入实验室造成的。 英文
图3.对四个d + d核聚变反应估算的速率。对于数据采集区间持续0.5~1小时的1,114条γ射线谱中的每一条,从信号中减去平均化的本底γ谱可以得到一条剩余γ谱。通过调节每一个反应的已知形式的γ射线谱的比例,对每一个剩余光谱进行拟合;拟合得到的数量级可以为正也可以为负。这里的图是所有1,114条γ谱的柱状图。在a和b中,速率以聚变的功率为单位(a: pW;b: mW);c和d中,反应速率为通常使用的单位(c: s–1;d: 103 s–1)。每一个图中,柱状图大致呈现为零点附近... | 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 | 对d(p, γ)3He反应放出的5.49 MeV的γ射线也进行了类似的搜索;最大的源放射拟合速率10 s–1对应于约10 pW的核聚变功率。 英文
在每个剩余γ谱中对整个0.1~25.5 MeV能量区间内高于本底的可能γ射线峰进行了总体搜寻。符合条件的可能情况需要有至少一个通道计数高于3σ(σ为那个通道计数的传递泊松误差),并且延展到取样能量处γ射线峰的半高宽的临近通道计数和要大于9σ。找到的唯一可能的γ射线峰是由于γ谱增益不完善的缩放和平均本底零点不准而造成的;这些可以通过其邻近的正漂移和负漂移的数量级相同,以及在一个已知的本底峰的位置过零点,来进行识别。没有发现其他的可能的γ射线峰。结合探测器效率,得到了γ射线放射速率限值和能量... | 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 | 不幸的是,在我们监测的831小时期间,我们并没有获得任何关于过剩热量产生的计算数据,所以我们不能够将核信号的缺失与异常热量的存在关联起来。 英文
图5.a,累积2.5小时的γ射线谱。其中包括一个约2小时的区间,在此期间在电解池2-1中观察到了D2O电解质沸腾。插图是对γ谱低能端的放大。b,扣除沸腾开始之前2.5小时累积的γ谱之后的剩余γ谱。低能量处的负盈余是源于发生在整个5小时期间的一个微小的(0.1%)增益漂移(这些γ谱没有经过再标定)。 英文
然而,我们被告知“曾经有两个小时的时间段内电解池2-1有过剩的热量释放......不幸的是,当时你们的计算机和探测器并没有在工作,因为在实验室发生断电之后,它们没有得到重启”(庞斯,个... | 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 | atomic precision. This capacity has allowed us to fabricate rudimentary structures of our own design, atom by atom. The processes we describe are in principle applicable to molecules also. In view of the device-like characteristics reported for single atoms on surfaces5,6, the possibilities for perhaps the ultimate in ... | 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 nickel sample was processed by cycles of argon-ion sputtering, annealing in a partial pressure of oxygen to remove surface carbon, and flash annealing. After cooling to 4 K the sample was imaged with the STM and found to be of acceptable quality. Figure 1a is an image of the surface taken under constant-current sca... | 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 | effectively terminates the attraction between the xenon and the tip, leaving the xenon bound to the surface at the desired location. 中文
Fig. 2. A schematic illustration of the process for sliding an atom across a surface. The atom is located and the tip is placed directly over it (a). The tip is lowered to position (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 | no significant effect on the threshold tip height. This suggests that the dominant force between the tip and the xenon atom is due to the Van der Waals interaction, but this tentative conclusion requires further investigation. 中文
In Fig. 3 we show a sequence of images demonstrating how a simple structure, the linear mu... | 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 anticipate that there will be a limiting class of adsorbed atoms and molecules that may be positioned by this method. Many new avenues of investigation are open to us. It should be possible to assemble or modify certain molecules in this way. We can build novel structures that would otherwise be unobtainable. This 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 | 英文
STM的探针尖端总是对被吸附原子施加一个有限的力。这个力中同时包含着范德华力和静电力的贡献。通过调整针尖的位置和电压,我们可以调节此力的大小和方向。此外,考虑到沿着表面移动原子比将其拖离表面更省力这一事实,我们可以通过设置这些参数,使STM针尖拉动一个原子穿过表面的同时,仍保持该原子结合在表面上。出于以下原因我们决定研究镍(110)面上的氙:表面电势起伏可以足够大,使得我们可以对氙原子成像,而又不会不经意地移动它们;另外在需要时,表面电势的起伏还可以足够小,使得我们可以施加足够的侧向力在表面上移动氙原子。 英文
实验在一台含有超高真空系统的STM上进行,同时系统被冷却至4 K。将容纳显微镜的整个样品室冷却至4 K,通过吸收残... | 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
图3.在镍(110)表面上构建线型氙原子链的各个阶段。在这些图像中单个氙原子显示为1.6 Å高的突出物。镍原子行看起来犹如明暗交替的条纹。可以看到镍表面有若干处点缺陷。a,已装配好的氙原子二聚体。在二聚体的右侧,一个氙原子已进入恰当的位置,准备形成一个三聚体。b,氙原子线型三聚体的形成。c~f,构建线形七聚体的各个阶段,这个过程能够在一小时内完成。氙原子间距为5 Å,各自占据相邻的镍表面单胞。 英文
我们预期将会有一类特定的被吸附的原子和分子可以用这种方法来定位。很多新的研究途径展现在我们面前。应该有可能以这种方式来组装或修饰某些分子。我们能够构建出用其他办法无法得到的新型结构。这将引出一系列新的表面研究工作,即利用STM... | 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 1985 Farman et al.1 reported that spring values of total column ozone over Halley Bay, Antarctica, had decreased considerably during the previous decade, and they suggested that certain chlorine-containing compounds could be causing the observed ozone depletion. Further studies have supported these findings2-5 and 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 | polar jet as a “containment vessel” is supported in the analyses of some authors1,14-16 but not by others17-22. 中文
Possible Arctic ozone loss has also been reported recently. Balloon data taken during 1989 suggest that ozone depletion occurred late in January at an altitude of 22–26 km over Kiruna, Sweden (68° N)23, 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 | first 8° of latitude inside the vortex boundary, comprising about 60% of the vortex volume) and the inner vortex (the remainder of the vortex, usually including the pole). The outer vortex receives more solar radiation than the inner vortex, and so photochemical ozone loss is more likely to occur there. 中文
An analysis ... | 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 | There are insufficient simultaneous measurements of lower stratospheric O3 and N2O available to determine an accurate climatology for these trace species, and so our analysis relies solely on the measurements made during AASE. An example of mid-latitude N2O and O3 data is given in Fig. 1a. These data are from an AASE 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 | that the data are from the inner vortex (all of vortex interior more than 8° of latitude inside the vortex boundary). e, Same as (b) except the data are from the exterior of the Antarctic vortex during AAOE (1987). 中文
Figure 1b represents all data with Θ > 400 K taken in the vortex exterior. Also shown are linear fits... | 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 | that the O3–Θ dependence is not a result of dynamics, but of chemistry. 中文
This O3–Θ dependence was also clearly seen in the Antarctic exterior (Fig. 1e) and seems much like the Arctic outer vortex (Fig. 1c). Also given in Fig. 1e is the Antarctic reference that was used for assessing O3 loss27. That reference was base... | 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 | Figure 2b confirms the O3 loss seen in Fig. 1a–d but in a spatial context, by plotting O3 against latitude relative to the vortex boundary for the same five N2O bins of Fig. 2a. Only data above 420 K are plotted, to exclude data that may be affected by the relatively unrestricted horizontal exchange of air at the botto... | 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 an increase of more than 15% is evident from 11 column measurements and 19 balloon soundings taken from 10 January to 8 February at 82°N (ref. 42). The column increase can only be explained by a poleward flux of mid-latitude air that carries more O3 into the polar vortex than is removed by dynamical or chemical pro... | 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 | could occur during warming events43 (isentropic) or from diabatic circulation into the vortex. The qualitative arguments that follow do not generally rely on either of these positions, but the arguments involved in quantifying O3 loss do. 中文
Searching for a possible explanation for the O3–Θ dependence that is consisten... | 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 | autumn and winter, and no such data are available. 中文
Returning to the O3–Θ dependence, a plausible explanation for the low O3 and its dependence on Θ can be constructed in the context of a “flowing processor”. First, recall that air is diabatically cooling both inside and outside the vortex, that N2O is chemically ine... | 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 | Similar reasoning can also be applied to Fig. 1b–d to again test our expanded hypothesis, this time assuming that there is mass flux into the lower vortex. Consider an air parcel with, for example, N2O = 175 p.p.b.v. originally outside the boundary at Θ= 470 K and O3 = 3,050 p.p.b.v. (Fig. 1b). Later that parcel contai... | 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 quantify O3 loss within the vortex, a linear least-squares fit to all the exterior data (Fig. 1b) is calculated, excluding those points at the bottom of the vortex where Θ<420 K. This fit is shown in Fig. 1c, d and is given by
where approximates the O3 mixing ratio in the vortex exterior from the mixing ratio of N2... | 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 O3 decrease of 13±8 p.p.b.v. per day has been reported by others35 also using AASE data. The analysis was restricted to a few vertical profiles within the vortex and required a diabatic cooling rate estimated from N2O and an assumption of strictly vertical descent. If the same cooling rates (0.9 K per day in Θ) are ... | 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 | January is too large to match these model studies. But meteorological data show that temperatures were low enough to form polar stratospheric clouds at 30 mbar by late November (A. F. Tuck, personal communication), and the eccentricity of the Arctic vortex is sufficient to frequently carry outer vortex air into sunlit ... | 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. 4. a, O3 and N2O data from 9 February 1989 are plotted against latitude relative to the boundary along a flight leg with Θ = 465±7 K. b, Same flight as in (a) except O3 – and ClO are plotted against latitude relative to the boundary. Negative values for O3 – indicate O3 loss relative to the vortex exterior. c, O3 ... | 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 | conservative cooling rate. Losses of 9–24 p.p.b.v. per day are obtained for parcels with N2O from 210 p.p.b.v. to 130 p.p.b.v., respectively. These rates are comparable to but slightly higher than model calculations. Larger cooling rates and deviations from vertical descent will both increase this difference. 中文
An O3 ... | 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 | Farman, J. C., Gardiner, B. G. & Shanklin, J. D. Nature 315, 207-210 (1985).
Hofmann, D. J., Harder, J. W., Rolf, S. R. & Rosen, J. R. Nature 326, 59-62 (1987).
de Zafra, R. L. et al. Nature 328, 408-411 (1987).
Solomon, S., Mount, G. H., Sanders, R. W. & Schmeltekopf, A. L. J. Geophys. Res. 92, 8329- 8338 (1987).
J. G... | 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 | Solomon, S., Garcia, R. R. & Stordal, F. J. Geophys. Res. 90, 12981-12989 (1985).
Garcia, R. R. & Solomon, S. J. Geophys. Res. 90, 3850-3868 (1985).
Brasseur, G. J. & Solomon, S. Aeronomy of the Middle Atmosphere 2nd Edn (Reidel, Dordrecht, 1986).
Perliski, L. M., Solomon, S. & London, J. Planet Space Sci. 37, 1527-153... | 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 Ed Danielsen, Stuart McKeen, George Mount, Susan Solomon, Michael Trainer and Adrian Tuck for their helpful comments, William Brune and Darin Toohey for the use of the ClO data, Melanie Steinkamp and Cynthia Proffitt for their help in Stavanger, Ken Aikin for producing the figures, and the ER... | 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 | 当太阳辐射量最低时,我们预期不会出现因光化作用而引起臭氧大量亏损的情况,而正如所预料的一样,在北极并未发现臭氧含量沿等熵面有明显下降的现象。 英文
本文的分析基于以Θ为垂直坐标、以相对于极涡边界的纬度为水平坐标的动态坐标系,其中极涡边界是由飞机上测定的峰值风速所在纬度决定的。边界的平均纬度为68°N,标准偏差为3°。在接下来的分析中,我们将数据分为三个不同的区域:极涡外部(从飞机起飞的位置59°N到极涡边界处)、外极涡(从极涡边界向内8个纬度,约构成整个极涡体积的60%)以及内极涡(剩下的极涡部分,一般包括极点)。外极涡接收到的太阳辐射多于内极涡,因此,外极涡发生臭氧光化亏损的可能性更大。 英文
采用与分析南极臭氧洞外存在臭氧亏损相... | 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 | 在图1b和c中O3含量亦随Θ值的降低而降低。N2O值恒定时,O3含量随Θ值的降低而减少的特征,可称为“O3–Θ的依赖关系”。极涡外部O3–Θ的相关性较小,在外极涡两者的相关性较大,不过,在中纬度地区以及内极涡中,两者则没有明显的相关性。图1b、c所示的O3–Θ的依赖关系并非空气从臭氧含量的最大值之上向下混合的结果,因为从O3含量的最大值往上,O3和Θ应呈负相关关系,而在图1b、c中两者之间为正相关。这说明,O3–Θ的依赖关系并非动力作用的结果,而是化学过程所致。 英文
从南极极涡外部的相关数据中(图1e)也可清楚地看到O3与Θ的这种依赖关系,而且与北极外极涡(图1c)颇为相似。图1e中还给出了用于评估南极O3亏损的参考系[27]。该... | 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 | 这就意味着,每一到两个月,就需要相当于25千米以上O3柱总量这样的量加入极涡的O3柱,再加上一份额外的量来平衡极涡底部流出的量。此外,倘若(2)是准确的,那么根据(1)推出的23千米以下O3柱总量的增加应该主要来源于平流层低层进入极涡的O3通量,而非垂直递减所致。该通量可能在变暖事件(等熵条件下)期间发生[43],也可通过非绝热循环作用进入极涡。虽然后来的许多定量论证都不是根据以上任何一个条件得出的,但相关的O3亏损的定性论证却是由此而来。 英文
既要解释O3与Θ之间的相关关系使之与图1a~d所示一致,冬季O3亏损量又不能过大,基于这两点考虑我们认为,臭氧的亏损可能是在冬季之前发生的。法曼等[45]提出了关于夏季极昼期间南极上空出现... | 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 | 也就是说,大量气流在飞机飞行高度上或附近穿过极涡边界就意味着边界内采到的空气样品是刚刚进入极涡的,仍带有外部气体的特征。平流层中存在更高的气流路径需要的前提是,O3与N2O之间的参照关系在飞机采样区域之上仍然保持不变,那么也就意味着O3的亏损量更不确定。图1a就支持了这一假定。 英文
为了量化极涡内O3的亏损,我们计算出了极涡外所有数据的线性最小二乘法拟合结果(图1b),剔除了极涡底部Θ < 420 K时的那些点。该拟合结果见图1c、d,其表达式为:
O*3(ppbv)= 7,019 – 22.42×N2O(ppbv)
其中,是根据N2O的混合比得到的极涡外O3混合比的近似值。对于在极涡内采到的所有样本,其值都可通过N2O的含量计算... | 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 | 极涡内O3与N2O之间的这种正相关关系与通常在边界外见到的负相关性恰恰相反,说明极涡内有O3亏损。图4b显示,边界外没有O3亏损,边界内则亏损严重(从O3 – 为负值可以看出),而O3的亏损恰好就在发生ClO显著增加的地方。图4c展示了外极涡中O3与ClO之间的这种关系在整个调查期间一直存在,而且即使在N2O含量不变时,这种关系也非常明显。该图所示为外极涡的全部数据,其中横坐标为ClO,纵坐标为O3 – ,Θ限制在435±15 K。所有数据均根据N2O的值作了严格的划分,并对每部分数据都作了线性拟合。很显然,在很广的N2O值范围内,O3亏损与ClO之间存在正相关关系,而且各部分的线性拟合结果都惊人地相似,尽管它们的斜率在N2O值较大... | 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 | Since the discovery of C60 in 1985, this exotic molecule had languished in limbo, since there was no proof of its alleged soccer-ball cage structure. That changed with the publication of this paper from the groups of Wolfgang Krätschmer in Heidelberg and Donald Huffman in Arizona, which described a way to make C60 in 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 | vibrational modes10-15, and the electric and magnetic properties16,17. There has been speculation on the possible chemical and industrial uses of C60 (ref. 2), and on its importance in astrophysical environments18-20. Until now, it has not been possible to produce sufficient quantities of the material to permit measure... | 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 | vacuum or in an inert atmosphere, thus subliming the C60 out of the soot (W. Schmidt, personal communication). The sublimed coatings are brown to grey, depending on the thickness. The refractive index in the near-infrared and visible is about two. To purify the material, we recommend removing the ubiquitous hydrocarbon... | 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 | low and high resolution are shown in Fig. 2. The spectra were obtained using a time-of-flight secondary-ion mass spectrometer23 and a C60-coated stainless-steel plate. In the mass range above 300 a.m.u., the spectrum is dominated by C60 ions and its fragments (even-numbered clusters of atomic carbon), and C70 ions. In ... | 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 determine if the C60 molecules form a regular lattice, we performed electron and X-ray diffraction studies on the individual crystals and on the powder. A typical X-ray diffraction pattern of the C60 powder is shown in Fig. 3. To aid in comparing the electron diffraction results with the X-ray results we have inset ... | 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. X-ray diffraction pattern of a microcrystalline powder of C60. Inset (upper left) is a single-crystal electron diffraction pattern indexed with Miller indices compatible with the X-ray pattern. The pattern is from a thin platelet such as those in Fig. 1 with the electron beam perpendicular to the flat face. 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 | In small crystals at least, the C60 molecules seem to assemble themselves into a somewhat ordered array as if they are effectively spherical, which is entirely consistent with the hypothesis that they are shaped like soccer balls. The excess between the nearest-neighbour distance (10.02 Å) and the diameter calculated 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 | Figure 4 shows the transmission spectrum of an ~2-μm-thick C60 coating on a silicon substrate. The infrared bands are at the same positions as previously reported21,22, with the four most intense lines at 1,429, 1,183, 577 and 528 cm–1; here, however, there is no underlying continuum remaining from the soot. In many 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 | Fig. 4. Infrared absorption spectrum of a coating, ~2 μm thick, of solid C60 on a silicon substrate, referenced to a clean silicon substrate. Apparent negative absorptions are due to the coating acting in part as a non-reflecting layer. 中文
Figure 5 shows an absorption spectrum taken on a uniform film coated on a quart... | 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 original stimulus for the work2 that led to the hypothesis of the soccer-ball-shaped C60 molecule, buckminsterfullerene, was an interest in certain unexplained features in the absorption and emission spectra of interstellar matter. These include an intense absorption band at 217 nm which has long been attributed to... | 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 | (C60). The various physical and chemical properties of C60 can now be measured and speculations concerning its potential uses can be tested. 中文
(347, 354-358; 1990)
W. Krätschmer*, Lowell D. Lamb†, K. Fostiropoulos* & Donald R. Huffman†
* Max-Planck-Institut für Kernphysik, 6900 Heidelberg, PO Box 103980, Germany
† Dep... | 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 | Krätschmer, W., Fostiropoulos, K. & Huffman, D. R. in Dusty Objects in the Universe (eds Bussoletti, E. & Cittone, A. A.) (Kluwer, Dordrecht, in the press).
Krätschmer, W., Fostiropoulos, K. & Huffman, D. R. Chem. Phys. Lett. 170, 167-170 (1990).
Steffens, P., Niehuis, E., Friese, T. & Benninghoven, A. Ion Formation fr... | 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 | 于是现在就可以详细地研究C60分子的固态与分子性质,以及它在星际空间中可能发挥的作用了。 英文
在碳蒸气中观察到了处于C30~C100范围内的偶数个碳原子簇[1]之后,已经找到了能使C60分子成为气化石墨产物主要成分的反应条件[2-4]。为了解释这种分子的稳定性,一种具有精巧结构的模型被提出来:其中碳原子排布于一个截角二十面体的60个顶点处,就像一个足球那样。这一结构——由于其测地学性质而被称为巴克敏斯特富勒烯[2]——曾是几种理论性稳定试验的对象[5,6],也曾在文献中进行过广泛的探讨。人们已经对其很多种物理性质进行了计算,其中包括电子能量[7-9]、光谱[9]、振动模式[10-15]以及电磁学性质[16,17]。曾有过关于C6... | 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 | 如同此前曾提出的[24],我们认为C70分子也具有闭合的笼状结构,或者是伸长的[24]或者是近似球形的[25]。更多关于这种新物质的质谱详细情况将另外发表。 英文
结构
为了确定C60分子是否形成规则晶格,我们对单个晶体和粉末进行了电子和X射线衍射研究。图3显示的是一张典型的C60粉末X射线衍射图。为了便于比较电子衍射结果与X射线衍射结果,我们在图3中插入了电子衍射图。在如图中所示确定指标的衍射点的六方排列中,推测8.7 Å的d间距对应于六方晶系中的(100)倒易晶格矢量。两类衍射之间最明显的对应关系存在于X射线图中位于5.01 Å处的峰与电子衍射图中的(110)点——它给出了约5.0 Å的间距。假定C60分子类似于叠放在六方密堆积... | 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 | 经过多次努力,终于成功地除掉了这一污染,方法是用乙醚清洗炭黑再用蒸馏苯提取。图4中的光谱就是将以这种方式清洗过的原料在真空条件下升华到基底表面而获得的。光谱几乎没有显示出CH杂质的迹象。参照四个强谱带的测定位置,已经有若干位研究者[10-15]对振动模式进行了计算。如同之前已经谈到的,只有四个强谱带存在,这对于这种具有很高对称性的截角二十面体自由分子来说是意料之中的。还有很多其他的弱红外谱线出现,它们可能是来自其他原因,其中可能包括C70分子的吸收,或者是由C60分子中12C以外的同位素所产生的对称性分裂,或者是由于固体中C60分子的相互作用。处于约2,330 cm–1和2,190 cm–1的较弱特征峰,位于自由CO2和CO伸缩模式... | 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
(王耀杨 翻译;周江 审稿)
Light-Emitting Diodes Based on Conjugated Polymers
J. H. Burroughes et al.
Editor’s Note
After the discovery of electrically conducting polymers in the 1970s, subsequent work identified several organic polymers with semiconducting electrical behaviour. One of them—poly (p-phenylene vinylene) or PPV—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 | THERE has been long-standing interest in the development of solid-state light-emitting devices. Efficient light generation is achieved in inorganic semiconductors with direct band gaps, such as GaAs, but these are not easily or economically used in large-area displays. For this, systems based on polycrystalline ZnS hav... | 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 | strong photoluminescence in a band centred near 2.2 eV, just below the threshold for π to π* interband transitions9,10. 中文
We synthesized PPV (I) using a solution-processable precursor polymer (II), as shown in Fig. 1. This precursor polymer is conveniently prepared from α,α′-dichloro-p-xylene (III), through polymeriza... | 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 stability of the PPV film allows easy deposition of the top contact layer, and we were able to form this contact using thermal evaporation for metals and ion-beam sputtering for indium oxide. 中文
Figures 2 and 3 show typical characteristics for devices having indium oxide as the bottom contact and aluminium as 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 | The observation and characterization of electroluminescence in this conjugated polymer is of interest in the study of the fundamental excitations of this class of semiconductor. Here, the concept of self-localized charged or neutral excited states in the nonlinear response of the electronic system has been a useful one... | 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 | Therefore, the charge carriers involved are probably polarons. The evidence that they can combine to form polaron excitons requires that the polaron gap states move no further into the gap than those of the polaron exciton and may account for the failure to observe the optical transitions associated with the polaron. 中... | 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 | Basescu, N. et al. Nature 327, 403-405 (1987).
Friend, R. H., Bradley, D. D. C. & Townsend, P. D. J. Phys. D20, 1367-1384 (1987).
Bradley, D. D. C. & Friend, R. H. J. Phys.: Condensed Matter 1, 3671-3678 (1989).
Bradley, D. D. C. J. Phys. D20, 1389-1410 (1987).
Murase, I., Ohnishi, T., Noguchi, T. & Hirooka, M. Synthet... | 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 | 但是,那些具有较宽半导体能隙并且可以制备成十分纯的形式来控制其在缺陷位处的激发态非辐射衰减的共轭聚合物,能够表现出高光致发光的量子效率。其中,聚对苯撑乙烯(PPV)能很方便地制成高质量的薄膜,并且在一个以2.2 eV为中心的带显示出很强的光致发光,刚好低于从π到π*的带间跃迁的阈值[9,10]。 英文
我们利用一种可溶液加工的前驱体聚合物(II)合成了PPV(I),如图1所示。该前驱体聚合物制备起来很方便,是由α,α′–二氯对二甲苯(III)通过锍盐中间产物(IV)的聚合[11-13]得到的。在碱性条件下的水/甲醇混合物中进行聚合。反应终止后,对反应混合物进行蒸馏水透析。除去溶剂,将前驱体聚合物重新溶于甲醇中。我们发现对于在适当基质... | 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
PPV的光致发光量子效率估算约为8%。研究表明[10,17]:无辐射跃迁过程限制光致发光中测得的辐射衰减效率,该无辐射过程是来自于激发态向作为无辐射复合中心的缺陷位点的迁移;而在高强度时,该无辐射过程还可归结为激发态对之间的碰撞。这些过程原则上是能够通过聚合物的设计来控制的,因此在一系列电致发光应用中发展这类材料具有极大的可能性。 英文
(王耀杨 翻译;于贵 朱道本 审稿)
Evidence for a Common Central-Engine Mechanism in all Extragalactic Radio Sources
S. Rawlings and R. Saunders
Editor’s Note
Qua... | 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 | by accretion: this high efficiency implies that the engine is a massive spinning black hole which both powers the jets and controls the accretion rate. 中文
WE have recently found a positive correlation between the narrow-line luminosities and the radio luminosities of an unbiased sample of low-redshift (z<0.5) Fanaroff... | 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 | because they scatter microwave-background photons by the inverse Compton process6. Where spectral ages are unavailable, we can estimate the age as follows. For a lobe of length D/2, width W and growth speed V = D/2T, we can relate the equipartition pressure peq in the lobe to the confining density ρ by ρV2 = kD2W–2peq;... | 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 | Table 1. Data for calculation of jet power
Equipartition energy was calculated assuming no energy in protons, minimum and maximum frequencies of 10 MHz and 10 GHz, and a volume-filling factor of one. Spectral ages T, where available, were taken from the literature (refs 6, 7, 14 for the FRIIs and refs 15–21 for the FRI... | 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 | 3C76.1 (ref. 23; an upper limit), 3C196 (ref. 24), 3C275.1 (ref. 25), the new identification for 3C326 (ref. 26), 3C334 (ref. 27), 3C338 (refs 8, 28). We measured a flux of Hα + [N II] of 7.5×10–18 W m–2 for NGC6251 during the observing run described in ref. 29. For 3C31, 3C66B and 3C465, we used the data in ref. 30, 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 | give quasars apparently higher LNLR at constant Q and thus similar Lrad. 中文
We now consider accretion rates, first in the low-Q (Q ≤ 1038 W) objects of Fig. 1. These often contain huge stored energies E (~1053 J, equivalent to 5×105 M⊙) and must therefore contain central masses ≥ 107 M⊙, with corresponding Eddington lu... | 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 | produced by a machine, which, to satisfy Fig. 1, must also control the accretion rate. A possible model involves jets that are driven by the extraction of rotational energy from a spinning black hole, ringed by an ion-supported torus13. Whatever the model, it must explain the two key features of the ratio of the output... | 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 | Rawlings, S. thesis, Univ. of Cambridge (1988).
Laing, R. A., Riley, J. M. & Longair, M. S. Mon. Not. R. astr. Soc. 204, 151-187 (1983).
Scheuer, P. A. G. in Superluminal Radio Sources (eds Zensus J. A. & Pearson T. J.) 104-113 (Cambridge University Press, 1987).
Barthel, P. D. Astrophys. J. 336, 606-611 (1989).
Jackso... | 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 P. Miller for help with compiling data on 3CR objects and P. Hughes for comments. SR is supported by a Research Fellowship at St John’s College Cambridge.
所有河外星系射电源有共同中央引擎机制的证据
罗林斯,桑德斯
编者按
类星体是“活动星系核”中最极端的例子,它们在狭小的空间内产生巨大的能量,但是观测特性变化很大。人们普遍认为其剧烈的能量产出是这些星系中心的大质量黑洞造成的,但却缺乏直接的证据。本文中,剑桥大学的史蒂夫·罗林... | 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 | 加入以上天体之后,在每个变量跨越大约四个量级的范围内,Q与LNLR相关,而且弥散仅为一个量级。最佳拟合曲线表明二者的关系接近正比。 英文
表1.喷流功率的计算数据
在均分能量的计算中,假定质子没有能量,最小和最大频率分别为10 MHz、10 GHz,体积填充因子为1。表中光谱年龄T(如果有的话)皆取自参考文献(关于FRII型的文献参见6、7、14,关于FRI型的文献参见15~21);在需要的地方,束缚电子数密度ne可以通过可用的X射线和光学数据进行估算[5,7],并且通过公式ρ=1.4nemp与气体密度ρ联系起来(mp是质子的静止质量)。这里研究的高红移FRII型射电源是9个z<1的3CR类星体(分别为:3C47、3C175、3C... | 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 | 对于超过该值的光致电离光度Lphot,考虑到观测到的LNLR≤1036 W,覆盖因子需要满足κ≤0.01,该值比类星体中观测到的要小(我们假定每10倍频程的光子流量具有相同的功率);而且,它们的低电离参数在窄线区将要求极端的气体密度(电子密度ne»108 m–3)的存在。因此,吸积率必须小于低Q值天体的爱丁顿极限。 英文
在高喷流功率的天体中,存贮在瓣中的能量相似,但是其Lphot比低Q值天体高得多,“超爱丁顿吸积”不能类似地被排除。如图1所示,吸积率从亚爱丁顿到超爱丁顿吸积范围内是Q的连续函数,然而,这一点在最近的贝尔(Bell)模型中也是可能的[12]。或者存在另一种可能,在所有的有射电喷流的天体中,吸积也许都是“亚爱丁顿吸积”... | 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 has been suggested1-3 that fertilizing the ocean with iron might offset the continuing increase in atmospheric CO2 by enhancing the biological uptake of carbon, thereby decreasing the surface-ocean partial pressure of CO2 and drawing down CO2 from the atmosphere. Using a box model, we present estimates of the maximu... | 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 plants is rather low, between 1:10,000 and 1:100,00015,16, the amount of iron required to carry out this fertilization is relatively modest: ~106 tons of iron per year assuming that all the iron goes into organic matter. Our model study differs from that of Peng and Broecker17 in the area fertilized (16% of the worl... | 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 | box of this area. Third is the reduction in CO2 partial pressure resulting from a given carbon removal. We have found that this is considerably larger at high rather than at low CO2 levels because of the nonlinear relation between PCO2 and ΣCO2. We use three different anthropogenic CO2 emission scenarios to examine 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 | The rate at which atmospheric CO2 is taken up by the oceans also depends on the rate at which the ocean circulation and mixing transport to the abyss the excess CO2 that invades the fertilized region from the atmosphere. As discussed below, we find that this factor is less critical than those mentioned above. Figure 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 | 14C are: K = 465+7,096 × exp(– (z – 75 m)/253 m) m2 yr–1; w = 0.44 m yr–1 (equivalent to 4.24×106 m3 s–1); u = 38 m yr–1 (69.8×106 m3 s–1); q = 0.00186 yr–1(79.5×106 m3 s–1); gas-exchange rate (g1, gh) at 280 p.p.m. = 15.1 mol m–2 yr–1; ocean surface area = 3.62×1014 m2; depth of mixed layer = 75 m; average depth of oc... | 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 | increases by only 88 p.p.m. after 50 years (60% of the increase in the unfertilized scenario) and by 310 p.p.m. after 100 years (74% of the increase in the unfertilized scenario). The decrease in atmospheric PCO2 resulting from iron fertilization reduces the low-latitude air–sea difference so that the response of the 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 | The higher the atmospheric concentration of CO2, the larger the change in oceanic PCO2 for a given reduction of ΣCO2 due to iron fertilization (see Fig. 2c). We find that the percentage reduction in atmospheric CO2 concentration which would occur after 100 years of iron fertilization decreases with higher CO2 levels (2... | 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 be effective, iron fertilization has to be applied continuously so that the atmosphere-ocean system does not revert to its unfertilized state. This is shown in Fig. 3, which shows what happens if iron fertilization is terminated after 50 years. At 50 years the ocean in the business-as-usual iron fertilization simula... | 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 | proportional to, the equilibrium warming, due primarily to the uptake of heat by the ocean. 中文
The most important conclusion we draw from our calculations is that, although the effect of iron fertilization is large enough to justify further study, the effect of a significant change in the emissions of CO2 is even large... | 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 | Toggweiler, J. R. & Sarmiento, J. L. in The Carbon Cycle and Atmospheric CO2: Natural variations Archean to Present Vol. 32, Geophysical Monograph Series (eds. Sundquist, E. T. & Broecker, W. S.) 163-184 (American Geophysical Union, Washington, DC, 1985).
Broecker, W. S. Peng, T.-H., Östlund, G. & Stuiver, M. J. Geophy... | 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 | 现在看来,铁施肥的效果似乎微乎其微。 英文
有学者提出[1-3],向海洋中投放铁可以增强生物对碳的吸收,从而降低海洋表面的CO2分压,使CO2得以从大气进入海洋并沉降下来,进而抵消大气CO2含量的持续增加。南大洋占世界大洋面积的16%,其水体中富含磷酸盐,在不断增加该水体中铁的假设下,我们利用箱式模型研究了铁施肥可能带来的最大效应,结果发现:假设无人类活动产生CO2排放,经过100年的铁施肥,大气中CO2的浓度将比未进行铁施肥时的值低59 ppm,而当计算中包含人类活动排放的CO2时,则会低90~107 ppm。然而在实际操作过程中,由于各种条件的限制,海洋不太可能吸收如此多的CO2,这些限制还需要进一步研究。铁施肥效应对南大洋生态... | 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
海洋对大气CO2的吸收速率也取决于大洋环流与混合流将进入铁施肥海域的过量CO2从大气传送到深海的速率。研究发现,该因素的影响比前面提到的其他因素要小一些,具体讨论如下。图1所示为我们采用的模拟大洋环流与混合流的模型。通过将模型与pre-bomb 14C(原子弹爆炸前放射性碳14同位素)测定结果以及布勒克等[19]在“地球化学海洋断面研究”(GEOSECS)计划中估计的原子弹爆炸总量进行拟合得到模型的各参数值(西根塔勒和约斯,发表于别处)。不过,在拟合过程中我们并未充分考虑南大洋的原子弹爆炸总量,因为很难从天然的14C背景下分辨出原子弹爆炸的信号;南大洋的数据也较少,尤其是来自原子弹爆炸前的数据;再者,46° S以南的原子弹爆炸... | 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“恒量排放”情景下,对世界大洋面积的16%进行铁施肥显示:100年导致大气中增加的CO2减少量为90 ppm。而还原至278 ppm的情景下则为59 ppm。“照常排放”情景下,由于大气中CO2浓度的进一步升高,该效应更明显:为107 ppm。当认识到PCO2与ΣCO2之间是一种非线性关系后,就很容易理解施铁作用与当前大气CO2浓度的依赖关系了。铁施肥带动的ΣCO2的减少量一定时,大气CO2浓度越高,海洋中PCO2的变化量越大(见图2c)。我们发现,经过100年的铁施肥后,大气CO2浓度降低的百分比会随着CO2浓度的升高而降低(在工业化以前的初始值情景下为21%,照常排放情景下为14%)。这点与彭和布勒克[17]的结论恰恰相反,他... | 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 discovery in 1990 of a method for making large quantities of the cage-like carbon molecule C60 led to intensive research into its physical and chemical behaviour. Here Art Hebard and colleagues at AT&T Bell Laboratories in New Jersey report one of the most striking outcomes of that work: when doped with alkali meta... | 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 sensitivity to air of alkali-metal-doped fullerenes (AxCn) limits the choice of sample preparation and characterization techniques. To avoid sample degradation, we carried out reactions with the alkali metal vapour and C60 in sealed tubes either in high vacuum or under a partial pressure of helium. The C60 was puri... | 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. 2. Temperature dependence of the electrical resistivity of a 960-Å-thick film of KxC60. 中文
A bulk polycrystalline sample of nominal composition K3C60 was prepared by reaction of 29.5 mg of C60 with 4.8 mg potassium. The amount of potassium was controlled volumetrically by using potassium-filled pyrex capillary tu... | 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 | corresponds to 1% volume fraction. This small fraction is possibly due to non-optimal doping or the granular nature of the sample. The large value of the Meissner effect for the field-cooled curve relative to the total exclusion, however, indicates bulk superconductivity in the electrically connected regions. 中文
Fig. ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\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 G. Dabbagh, S. J. Duclos, R. H. Eick, A. T. Fiory, R. M. Fleming, M. L. Kaplan, K. B. Lyons, A. V. Makhija, B. Miller, A. J. Muller, K. Raghavachari, J. M. Rosamilia, L. F. Schneemeyer, F. A. Thiel, J. C. Tully, R. Tycko, R. B. Van Dover, J. V. Waszczak, W. L. Wilson and S. M. Zahurak for val... | 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
用超导量子干涉磁强计测试了标称成分为K3C60的样品的直流磁化随温度变化的关系(如图3所示)。在零场中,冷却样品到2 K,再对样品加50 Oe的磁场。加热温度直到18 K时,样品都可将该场排出;这就证明了一个超导相的存在。通过在50 Oe的场冷却,已明确地说明了样品中超导性的体特征。温度低于18 K时出现了明显的迈斯纳效应(磁通排出)。磁化曲线的形状,特别是低温下与温度无关的现象,表明该样品具有良好的超导性。同样值得我们注意的是相当狭窄的转变温度范围。零场冷却曲线对应的磁通排出的大小表明超导体积比为1%。如此小的超导体积比可能是由于非理想掺杂或者是样品的粒状性质。但是,场冷却曲线的迈斯纳效应相对于总排出量的大的数值表明样品电连... | 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 | vertices correspond to the branch points of junctions. Here, we report the construction from DNA of a covalently closed cube-like molecular complex containing twelve equal-length double-helical edges arranged about eight vertices. Each of the six “faces” of the object is a single-stranded cyclic molecule, doubly catena... | 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. The synthetic scheme used to synthesize the cube-like object. This diagram illustrates the strand identification used in the text. Numbers refer to strand numbers. We have used the convention that as a new strand is formed by ligation, its identification changes from one or more numbers to a letter correspondin... | 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 | individual strands are: strand 1: CTTGCTCATACTGCATTCGGCCAGCCTGACATCA-CCGTGTACGCCCAAACCTTTCAACTTAGATGGTAGAAGGAGGGCAG; strand 2: CGCTGTGGGTCA-GGCTGGCCGAATGCAGAGCCAATCCTTGG; strand 3: GATTGGCTTATGAGCAAGCTGCCCTCCTC-GTTAGTT; strand 4: CTGGAACTAACGTCTACCATCTAAGTTGAAAGTCTCTTG; strand 5: GTGACCA-AGAGAGTTTGGGCGTACACGGTGATCCACAG... | 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 desired product by native gel electrophoresis. The topmost band (top of the well) contains a complex of smaller species that cannot penetrate the gel. The DNA molecules used are synthesized on an Applied Biosystems 380B automatic DNA synthesizer, removed from the support and deprotected using routine phosphoramidit... | 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 | final closure are each about 10%. 中文
Fig. 3. The products of the first ligation (ends C and D). Autoradiogram of a denaturing gel illustrating the products of ligating two quadrilaterals together at ends C and D. Kinase labelling and ligations were as described7. The quadrilaterals are radioactively labelled on the F ... | 400套付费套装书 |
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