The Australian geographer, 1928–1988     

Don Biddle 《The Australian geographer》1988,19(1):3-6

  相似文献   

The disappearance of OH from comet P/Encke     

Michael F. A&#x;Hearn  Robert L. Millis  Don T. Thompson 《Icarus》1983,55(2):250-258

Photoelectric observations of Comet P/Encke during its 1980 apparition are combined with other published data to relate molecular production rates to the visual lightcurve. In addition to a substantial asymmetry about perihelion which is already well known, there are shorter-term variations in specific molecules which have not been duplicated by models. The most dramatic of these fluctuations is a rapid decrease by more than a factor of 3 in the production of OH at 0.75 AU preperihelion.  相似文献   

Density fronts in the vicinity of a long ridge     

Frimann Hreinsson  Xiuzhang Zhang  Don L. Boyer 《Dynamics of Atmospheres and Oceans》1998,27(1-4)

Laboratory experiments concerning the nature of density fronts in a two-layer fluid in the vicinity of a continuous ridge were conducted. The experiments were carried out in a circular rotating test cell containing an annular ridge of uniform cross-section. The density fronts were established by releasing a lighter fluid contained in a bottomless cylinder in the interior of the region defined by the topography into a heavier fluid occupying the rest of the test cell. The system was also equipped with an oscillating plunger located along the test cell axis to produce simulated tidal currents impinging in the normal direction on the ridge; experiments without and with tidal forcing were conducted. The governing parameters for the physical system considered are the Rossby, temporal Rossby, Burger and Ekman numbers and geometrical parameters. It is found that for both the non-forced and tidally forced experiments the fronts were stabilized by the ridge. The fronts in the simulated tidal currents experiments were found to advect radially outward more rapidly at early times than their non-forced counterparts; at large times, the temporal evolution of the front for these forced experiments approached that of the non-forced experiments. In the region interior to the annular ridge, the motion field is highly baroclinic, while outside this region, the flow response at the forcing frequency is barotropic. Scaling arguments regarding frontal position, viscous decay and barotropic oscillatory flow responses are advanced and supported by experimental observations.  相似文献   

Chemical interdiffusion of dacite and rhyolite: anhydrous measurements at 1 atm and 10 kbar,application of transition state theory,and diffusion in zoned magma chambers   总被引：2，自引：2，他引：0  

Don R. Baker 《Contributions to Mineralogy and Petrology》1990,104(4):407-423

Chemical diffusivity measurements have been made on anhydrous metaluminous diffusion couples of dacite and rhyolite at 1 atm, 1200°–1400° C, and 10 kbar, 1300°–1600° C, and on anhydrous peraluminous and peralkaline dacite-rhyolite diffusion couples at 10 kbar, 1300°–1600° C. Chemical diffusivities for Si, Al, Fe, Mg, and Ca were measured in all experiments on the metaluminous diffusion couples using Boltzmann-Matano analysis, and Si diffusivities were measured on the other diffusion couples. Two 10 kbar metaluminous experiments were analyzed with the X-ray microprobe and diffusivities of Sr, Y, Zr and Nb were measured. Si diffusivity displays a weak negative correlation with SiO₂ content over the range of 65%–75% SiO₂. At a given SiO₂ content chemical diffusivities of all non-alkali elements are usually within less than an order of magnitude of Si chemical diffusivity and are controlled by partitioning along the diffusion profile so as to maintain local equilibrium at each point along the profile. Alkali chemical diffusivities were not measured but can be estimated from the experiments to be orders of magnitude higher than non-alkali chemical diffusivities. Data were fit to Arrhenius equations for diffusivities measured at 65, 70 and 75% SiO₂. At 1 atm the Arrhenius equation for non-alkalies at 70% SiO₂ in the metaluminous system is:

相似文献    135. Time variation of martian regional contrasts      Don T. Thompson 《Icarus》1973,20(1):42-47 Observations of contrast changes in blue light on Mars in 1969 and 1971 are presented. Seasonal effects evidently can be evaluated from these data, although nonseasonal effects are also present. A diurnal variation is noted for certain features during both apparitions. This variation cannot be fully accounted for without considering meteorological effects. An example of a contrast reversal in ultraviolet light is presented. The suggestion is made that during the Martian season covered herein, variability of the bright areas controlled the apparent contrasts observed.  相似文献    136. Lunar stratigraphy and sedimentology: John F. Lindsay. Elsevier,Amsterdam/Oxford/New York, 1976. xii + 302 pp. $28.95      Don E. Wilhelms 《Icarus》1977,32(4):471-472   相似文献    137. Understanding spatio-temporal rainfall-runoff changes in a semi-arid region      Santosh K. Aryal  Richard P. Silberstein  Guobin Fu  Geoff Hodgson  Stephen P. Charles  Don McFarlane 《水文研究》2020,34(11):2510-2530   相似文献    138. 西藏雅鲁藏布蛇绿岩形成构造环境的地球化学鉴别   总被引：9，自引：7，他引：2   李文霞  赵志丹  朱弟成  董国臣  周肃  莫宣学  DePAOLO Don  DILEK Yildirim 《岩石学报》2012,28(5):1663-1673 本文对西藏雅鲁藏布蛇绿岩带中部日喀则地区夏鲁蛇绿岩中的基性岩石进行了元素地球化学研究。岩石为低钾亚碱性玄武质岩石,具有低TiO2(0.64%～1.5%)、低K2O(<0.69%)、富Na2O(2.5%～6.0%)、烧失量普遍较高(2.0%～7.5%)的特征,表明样品普遍遭受蚀变。岩石具有与N-MORB类似的稀土元素和总体一致的微量元素特征,但是岩石明显富集大离子亲石元素和亏损高场强元素,显示了洋脊玄武岩向着岛弧岩浆作用的过渡趋势。日喀则蛇绿岩不是典型的洋中脊成因,应为SSZ型蛇绿岩,可能形成于与洋内俯冲有关的SSZ型的弧后或者弧前盆地中。对东西延伸超过1500km的雅鲁藏布蛇绿岩246套基性岩石形成的构造环境进行的地球化学判别,表明至少存在大陆岛弧型、地幔柱-洋内热点型、洋中脊-大洋岛弧型和典型大洋岛弧型等四种类型洋壳,揭示了特提斯洋存在多种构造环境的特征,有利于恢复和还原一个长期演化的、丰富的特提斯洋。  相似文献    139. Erratum to: Chemical interdiffusion of dacite and rhyolite: anhydrous measurements at 1 atm and 10 kbar, application of transition state theory, and diffusion in zoned magma chambers      Don R. Baker 《Contributions to Mineralogy and Petrology》2010,159(4):597-597   相似文献    140. Effects of BPA and DES on longchin goby (Chasmichthys dolichognathus) in vitro during the oocyte maturation      Baek HJ  Hwang IJ  Kim KS  Lee YD  Kim HB  Yoo MS 《Marine environmental research》2007,64(1):79-86 This study was performed in order to assess whether bisphenol (BPA) and diethylstilbestrol (DES) had agonistic or antagonistic effects on oocyte maturation using marine fish. We tested the effects of these chemicals on in vitro maturation, germinal vesicle breakdown (GVBD), assay using oocytes from the longchin goby, Chasmichthys dolichognathus. During the maturation process, low concentrations of BPA and DES triggered GVBD depending on the stage of oocyte development; BPA at 0.044 nM and DES at 0.037, 0.37, and 3.73 nM induced GVBD in 0.82-0.88 mm diameter oocytes (germinal vesicle located near the center of oocytes). In 0.76-0.80 mm diameter oocytes (fully vitellogenic oocytes), BPA induced GVBD at relatively higher concentrations (4.38, 43.8, and 438 nM). In 0.86-0.90 mm diameter oocytes, BPA and DES had no observable effect on GVBD at the concentrations tested. Oocytes with diameters between 0.82 and 0.88 mm appeared to be more sensitive to these chemicals. Moreover, our results showed that BPA and DES did not inhibit GVBD.  相似文献    [首页] « 上一页 [9] [10] [11] [12] [13] 14 [15] [16] [17] [18] [19] 下一页 » 末  页»