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101.
Samuel Heinrich Schwabe, the discoverer of the sunspot cycle, observed the Sun routinely from Dessau, Germany during the interval
of 1826–1868, averaging about 290 observing days per year. His yearly counts of ‘clusters of spots’ (or, more correctly, the
yearly number of newly appearing sunspot groups) provided a simple means for describing the overt features of the sunspot
cycle (i.e., the timing and relative strengths of cycle minimum and maximum). In 1848, Rudolf Wolf, a Swiss astronomer, having
become aware of Schwabe's discovery, introduced his now familiar ‘relative sunspot number’ and established an international
cadre of observers for monitoring the future behavior of the sunspot cycle and for reconstructing its past behavior (backwards
in time to 1818, based on daily sunspot number estimates). While Wolf's reconstruction is complete (without gaps) only from
1849 (hence, the beginning of the modern era), the immediately preceding interval of 1818–1848 is incomplete, being based
on an average of 260 observing days per year. In this investigation, Wolf's reconstructed record of annual sunspot number
is compared against Schwabe's actual observing record of yearly counts of clusters of spots. The comparison suggests that
Wolf may have misplaced (by about 1–2 yr) and underestimated (by about 16 units of sunspot number) the maximum amplitude for
cycle 7. If true, then, cycle 7's ascent and descent durations should measure about 5 years each instead of 7 and 3 years,
respectively, the extremes of the distributions, and its maximum amplitude should measure about 86 instead of 70. This study
also indicates that cycle 9's maximum amplitude is more reliably determined than cycle 8's and that both appear to be of comparable
size (about 130 units of sunspot number) rather than being significantly different. Therefore, caution is urged against the
indiscriminate use of the pre-modern era sunspot numbers in long-term studies of the sunspot cycle, since such use may lead
to specious results. 相似文献
102.
Since the rejection of the bubble flow conceptual model for in situ air sparging, most practitioners have adopted the conceptual model of air channeling, which generally implies the development of widely spaced, discreet air channels that bypass large regions of the subsurface. While air channeling clearly develops in response to stratigraphic heterogeneity, the universality of widely spaced air channels in homogeneous media is not supported by available evidence. Air channeling results in low bulk air saturation due to bypassing, and field and laboratory measurements of air saturations and previously published studies were used to evaluate if air channeling is realistic. The results indicated that homogeneous coarse sands are prone to the development of air channeling, and that homogeneous fine sands show higher air saturations and are not prone to air channeling. Breakthrough air saturations, which represent the minimum air saturations, that will conduct air flow, of approximately 0.02 to 0.04 were observed in coarse sands. In contrast, breakthrough air saturations of 0.10 to 0.13 were observed in fine sands and medium sands. The transition between these behaviors falls at about 15 to 20 cm water air entry pressure. These result indicate that, at both the field and laboratory scale, coarse sands are more prone to air channeling and bypassing than fine sands. Additionally, the larger air gradients and capillary pressures in fine sands result in a less buoyancy-dominated flow pattern, with a larger lateral extent of air flow. 相似文献
103.
It is well-known that the application of the Square-Root-of-Sum-of-Squares (SRSS) method in seismic analysis for combining modal maxima can cause significant errors. Nevertheless, this method continues to be used by the profession for significant buildings. The purpose of this note is to present an improved technique to be used in place of the SRSS method in seismic analysis. A Complete Quadratic Combination (CQC) method is proposed which reduces errors in modal combination in all examples studied. The CQC method degenerates into the SRSS method for systems with well-spaced natural frequencies. Since the CQC method only involves a small increase in numerical effort, it is recommended that the new approach be used as a replacement for the SRSS method in all response spectrum calculations. 相似文献
104.
Steven C. Schimmel James M. Patrick Linda F. Faas Jerry L. Oglesby Alfred J. Wilson 《Estuaries and Coasts》1979,2(1):9-15
Two long-term studies were conducted to determine toxicity, uptake and depuration of Kepone in blue crabs (Callinectes sapidus). In the first, Kepone was administered to crabs in seawater (0.03 or 0.3 μg Kepone/I) or food (eastern oyster,Crassostrea virginica, containing 0.25 μg/g Kepone). Uptake of Kepone in 28 days was primarily through the contaminated oysters. When these crabs were held in Kepone-free seawater and fed Kepone-free oysters for 28 days, no loss of the insecticide was evident. There were adverse effects on molting and survival in crabs fed oysters that contained 0.25 μg/g Kepone. A second study was conducted to determine: (1) the depuration of Kepone over a 90-day period in blue crabs fed oysters from the James River, Virginia (containing 0.15 μg/g Kepone); and (2) the effects of Kepone on molting and survival of blue crabs fed James River oysters or laboratory-contaminated oysters that contained 0.15 or 1.9 μg/g Kepone. Crabs fed Kepone-contaminated oysters followed by a diet of Kepone-free oysters for 90 days had detectable concentrations of the insecticide in tissues. Also, blue crabs that ate oysters containing Kepone in concentrations similar to those found in oysters from the James River, died or molted less frequently than crabs fed Kepone-free oysters meats. 相似文献
105.
106.
Allan F. Wilson 《Contributions to Mineralogy and Petrology》1976,55(2):131-138
Data from analyses of three coexisting pairs of pyroxenes with a wide range of Fe content from each of two localities are used to show the large systematic variation and predictable correlation of Fe (or Mg) of a pyroxene with its content of Al, Mn and Na in mafic granulites. Comparisons of pyroxenes can then be made more meaningful by normalizing Al, or other elements, to an appropriate Mg value. As both P and T may affect the element distribution of the two pyroxenes differently (especially Al and Na) the factor used in normalizing is found to vary from region to region. 相似文献
107.
Plagioclase in the range An2-An10 in a relatively undeformed Quartz—feldspar pegmatite is compared with similar material in a strongly deformed and recrystallized shear zone. Optical and transmission electron microscope observations and chemical data are discussed in terms of established mechanisms of strain induced recrystallization.Recrystallization occurs by the formation of subgrains from recovery, and their subsequent growth by boundary migration or coalescence by rotation. It is suggested that the recrystallization and grain growth are enhanced by a small increase in the anorthite content. Peristerite formation in the recrystallized grains is associated with the migration of high angle boundaries under upper greenschist facies conditions. 相似文献
108.
Allan F. Wilson 《Contributions to Mineralogy and Petrology》1976,56(3):255-277
Three pairs of coexisting pyroxenes of mafic granulites from each of two locations 100 km apart show large chemical differences, especially in Al, Fe, Mn, Ti and Na. Al content of the pyroxenes at the higher pressure locality is more nearly independent of Al of the host rock than are the pyroxenes from the lower pressure locality. All the data confirm that although no significant difference in temperature has emerged, there was a large difference in pressure between the two localities. Al is found to be a more effective discriminant of metamorphic conditions than
. As the three pairs of pyroxenes cover a wide range of Fe at each locality, the close relationship of Al and Na (and of Ca-tschermak and jadeite) to Fe becomes evident. This shows that a normalizing procedure should be adopted before comparing localities with different Al, Mn, Ti, Na and other elements or derived components such as jadeite and Ca-tschermak. 相似文献
109.
Epstein and Yapp's criticism of our paper is answered. It is shown that for all trees so far studied, the cellulose laid down in a warmer period contains C-H hydrogens depleted in deuterium with respect to cellulose laid down in a colder period. Since this is the opposite to that predicted by thermodynamics it is probably due to the temperature effects on one or more of the biochemical reactions leading to cellulose. 相似文献
110.
Metamorphic biotites examined by transmission electron microscopy contain planar defects on the (001) plane, superlattices, twins and a microstructure causing streaking of k≠3n rows. Analysis of the fringe contrast shows that the fault vectors associated with the planar defects are either R 1=±1/3 [010], R 2=±1/6 [310] or R 3=±1/6 [3 \(\bar 1\) 0]. Structural considerations indicate that a stacking fault R 1, R 2 or R 3 is most likely to exist in the octahedral layer rather than the potassium layer. The result of such a fault on a unit layer of mica is effectively to rotate it through ±120° about c* (equivalent to the common mica twin law). These stacking faults can provide the mechanism for producing the ±120° rotations associated with the common mica polytypes. Furthermore, many of the observed microstructures can be generated by these stacking faults. 相似文献