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121.
Chen Jian-sheng Donald C. Morton Bruce Peterson Allen Wright David Jauncey 《Chinese Astronomy and Astrophysics》1981,5(3):337-341
Based on the spectra of 4 high-redshift quasars (resolution 2A) obtained by us [1–5] using IPCS on the RGO Cassegrain spectrograph of the AAT, we point out the following. 1. Auto-correlation peaks at
in PKS 0805+046 and PKS 1442+101 suggest that the large number of absorption lines shortward of Lα in high redshift quasars are due to absorption by hydrogen clouds. 2. The distribution of absorption lines and the correlation function of
indicate that PKS 0528-250 may be an exception, requiring further observation. 3. Absorption redshift systems containing metallic lines may be produced by either matter ejected from the quasar, or an associated galaxy cluster or an intervening galaxy. 4. The randomness in the column density and the dispersion velocity deduced from the curve of growth of the
pair supports the hypothesis that the pure Lα absorption comes from primitive hydrogen clouds in the early, exploding universe. 5. The number of hydrogen clouds per unit redshift interval is determined by the data of absorption lines of quasars with Z > 3. 相似文献
122.
Petrology and genesis of natrocarbonatite 总被引:6,自引:0,他引:6
Tony D. Peterson 《Contributions to Mineralogy and Petrology》1990,105(2):143-155
Microprobe analyses of phenocrysts and groundmass, and crystal-size distributions of phenocrysts of pahoehoe natrocarbonatite lavas of the 1963 eruption of Oldoinyo Lengai have been determined. Nyerereite phenocrysts are homogeneous, with average composition Nc41Kc9Cc50 (neglecting F, Cl, P2O5, and SO3) where Nc=Na2CO3, Kc=K2CO3, and Cc= (Ca,Sr)CO3. Gregoryite phenocrysts have turbid, pale brown, oscillatorily zoned cores (average composition Nc77Kc5Cc18) with 0–30% oriented inclusions of exsolved nyerereite. Overgrowths on gregoryites (30 m wide) are relatively sodic (Nc81Kc4Cc15) and are free of inclusions. Cores and rims are rich in SO3 (4%) and P2O5 (2%). Blebs of pyrite-alabandite mixtures (100 m) occur in the groundmass. The groundmass has the simplified composition Nc65Kc15Cc20, less calcic than the composition of the 1-kbar nyerereite+gregoryite +liquid cotectic in the ternary system Nc-Kc-Cc. Groundmass quench growth of alkali halides + carbonate was followed by slower growth of coarse-grained and irregular gregoryite +KCl+BaCO3. Crystal size distributions of gregoryite and nyerereite in one sample are linear, implying little loss or gain of phenocrysts by crystal settling. AverageG is 0.15 mm, compared toG=0.03 mm for combeite phenocrysts from consanguineous nephelinite. Assuming an equal residence time () for both lavas, the apparent crystal growth rate (G) in carbonate melt is 5 times greater than in peralkaline undersaturated silicate melt. Data from experiments with natrocarbonatite and related synthetic systems indicate that Na–K–Ca carbonatite magmas which crystallize calcite cannot fractionate to nyerereite+gregoryite +liquid assemblages. Natrocarbonatites plot in the liquidus field of nyerereite, and minor fractionation of nyerereite to produce the erupted lavas is indicated. The term natrocarbonatite has been inappropriately applied to other eruptive rocks with calcite phenocrysts, and the only known occurrence of gregoryite-bearing natrocarbonatite is Oldoinyo Lengai. Natrocarbonatite probably originates by liquid immiscibility from strongly peralkaline nephelinites, which have also been erupted at Oldoinyo Lengai. 相似文献
123.
Light scattering profiles and water samples for filtration of suspended particulate matter were obtained during fall, 1973, from Ice Island T-3, then located about 50 miles north of Ellesmere Island. The profiles reveal almost no variability in scattering, either in the water column, or in time during our two weeks of field work. Gravimetric analysis of the filtered suspended particulate matter shows that mass concentrations are low, averaging about 7g l–1, and that they too remain very constant. The four water masses present in the Arctic Ocean could not be distinguished by our observations of light scattering and mass concentration of suspended particulates. 相似文献
124.
二氧化碳—气候相关关系人们在继续努力 ,试图搞清较大时间范围CO2 与气候的相关关系。得克萨斯A &M大学CrowleyT将最近重建的过去1000a期间北半球温度和气候摸式与能量平衡气候模式进行了对比研究 ,发现在人类出现前的记录中 ,十年区间的温度变化有64 %可以直接归因于日光幅射和火山作用的变化。然而 ,这一时序除温室气体以外的所有作用力的改变导致20世纪末期气温升高极其显著 ,与推测的温室气体作用力的影响相符合。Crowley 的分析进一步证实 ,温室效应已成为气候体系中自然变化以外的因素。剑桥大学Sha… 相似文献
125.
Batch experiments were performed to investigate cephapirin (a widely used veterinary antibiotic) adsorption on various size
sands of low total organic carbon content (0.08–0.36 wt%). In the aqueous concentration range investigated (11–112 μmol/L
cephapirin), adsorption to nearly pure quartz filter sands (0.50–3.35 mm diameter) is low. Isotherms are S-shaped and most
display a region of minimum adsorption, where decreased adsorption occurs with increasing solution concentration, followed
by increased adsorption at higher concentrations. Cephapirin adsorption to quartz-rich, feldspar-bearing dune sands (0.06–0.35 mm
diameter), and the smallest quartz filter sand investigated (0.43–0.50 mm), can be described by linear sorption isotherms
over the range of concentrations investigated. Distribution coefficients (K
d) range from 0.94 to 3.45 L/kg. No systematic relationship exists between grain size and amount of adsorption for any of the
sands investigated. Cephapirin adsorption is positively correlated to the feldspar ratio (K-feldspar/(albite + Ca-plagioclase).
Feldspar-ratio normalization of distribution coefficients was more effective than organic carbon normalization at reducing
variability of K
d values in the dune sands investigated. 相似文献
126.
BM Macey KW Christison J de Goede L Hutchings CD van der Lingen 《African Journal of Marine Science》2016,38(2):269-273
Catches of South African sardine Sardinops sagax have declined in recent years from about 200 000 t harvested annually during the period 2002–2006 to less than 100 000 t. Consequently, some companies are now importing sardine from sources elsewhere in the world to meet local demand for canned sardine and bait. This importation has the potential for the introduction of sardine pathogens, in particular the pilchard herpesvirus (PHV), which could have a negative impact on the currently small South African sardine population. The aims of the current study were to determine whether PHV is present in the local sardine population and to assess the extent to which sardine is being imported into the country and whether imported fish are from countries where the virus is known to be endemic. Fish sampled from South Africa’s western (n = 150), southern (n = 182) and eastern (n = 96) putative stocks of S. sagax were analysed for the presence of PHV using real-time quantitative polymerase chain reaction (qPCR). The origin and amount of potentially infected material imported into South Africa during the period 2010–2014 was also assessed. None of the South African sardine collected during this study tested positive for PHV, suggesting that active PHV was not prevalent in the local population of S. sagax at the time of this study. Between 56 000 and 71 000 t of frozen sardine was imported annually into South Africa from countries where S. sagax occurs, including some from areas (Australia and New Zealand) where sardine infection by PHV is known to be endemic. Hence, it is plausible that the PHV pathogen, capable of perpetuating infections in local sardine populations, could be imported into South Africa along with the importation of frozen sardine. Should local sardine be naïve to the virus, as suggested by this study, then the population is at risk of infection and precautions against such must be taken. 相似文献
127.
Estimation of aquifer hydraulic properties is essential for predicting the response of an aquifer to extractions and hence estimating the availability of the groundwater resources. Aquifer tests are commonly used for the estimation of aquifer properties; however, they can be expensive and often only characterize the short‐term response of the aquifer. This paper presents a time series modelling approach to estimating aquifer hydraulic properties. It is applied to 42 bores monitoring an unconfined aquifer within an irrigation region of south‐eastern Australia, and the resulting probabilistic estimate of hydraulic properties are evaluated against pumping test estimates. It is demonstrated that the time series modelling can provide a reliable estimate of the hydraulic properties that are typical of a very long‐term pumping test. Furthermore, the application of the time series modelling to 42 bores provided novel insights into the aquifer heterogeneity. We encourage others to further test the approach and the source code is available from: http://www.mathworks.com/matlabcentral/fileexchange/48546‐peterson‐tim‐j‐groundwater‐statistics‐toolbox Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
128.
Seasonal and Annual Fluxes of Nutrients and Organic Matter from Large Rivers to the Arctic Ocean and Surrounding Seas 总被引:3,自引:0,他引:3
Robert Max Holmes James W. McClelland Bruce J. Peterson Suzanne E. Tank Ekaterina Bulygina Timothy I. Eglinton Viacheslav V. Gordeev Tatiana Y. Gurtovaya Peter A. Raymond Daniel J. Repeta Robin Staples Robert G. Striegl Alexander V. Zhulidov Sergey A. Zimov 《Estuaries and Coasts》2012,35(2):369-382
River inputs of nutrients and organic matter impact the biogeochemistry of arctic estuaries and the Arctic Ocean as a whole, yet there is considerable uncertainty about the magnitude of fluvial fluxes at the pan-Arctic scale. Samples from the six largest arctic rivers, with a combined watershed area of 11.3?×?106?km2, have revealed strong seasonal variations in constituent concentrations and fluxes within rivers as well as large differences among the rivers. Specifically, we investigate fluxes of dissolved organic carbon, dissolved organic nitrogen, total dissolved phosphorus, dissolved inorganic nitrogen, nitrate, and silica. This is the first time that seasonal and annual constituent fluxes have been determined using consistent sampling and analytical methods at the pan-Arctic scale and consequently provide the best available estimates for constituent flux from land to the Arctic Ocean and surrounding seas. Given the large inputs of river water to the relatively small Arctic Ocean and the dramatic impacts that climate change is having in the Arctic, it is particularly urgent that we establish the contemporary river fluxes so that we will be able to detect future changes and evaluate the impact of the changes on the biogeochemistry of the receiving coastal and ocean systems. 相似文献
129.
Lydie Herfort Tawnya D. Peterson Fredrick G. Prahl Lee Ann McCue Joseph A. Needoba Byron C. Crump G. Curtis Roegner Victoria Campbell Peter Zuber 《Estuaries and Coasts》2012,35(3):878-891
The localized impact of blooms of the mixotrophic ciliate Myrionecta rubra in the Columbia River estuary during 2007–2010 was evaluated with biogeochemical, light microscopy, physiological, and molecular data. M. rubra affected surrounding estuarine nutrient cycles, as indicated by high and low concentrations of organic nutrients and inorganic nitrogen, respectively, associated with red waters. M. rubra blooms also altered the energy transfer pattern in patches of the estuarine water that contain the ciliate by creating areas characterized by high primary production and elevated levels of fresh autochthonous particulate organic matter, therefore shifting the trophic status in emergent red water areas of the estuary from net heterotrophy towards autotrophy. The pelagic estuarine bacterial community structure was unaffected by M. rubra abundance, but red waters of the ciliate do offer a possible link between autotrophic and heterotrophic processes since they were associated with elevated dissolved organic matter and showed a tendency for enhanced microbial secondary production. Taken together, these findings suggest that M. rubra red waters are biogeochemical hotspots of the Columbia River estuary. 相似文献
130.
Suzanne E. Tank Manfredi Manizza Robert Max Holmes James W. McClelland Bruce J. Peterson 《Estuaries and Coasts》2012,35(2):401-415
Although the Arctic Ocean is the most riverine-influenced of all of the world’s oceans, the importance of terrigenous nutrients
in this environment is poorly understood. This study couples estimates of circumpolar riverine nutrient fluxes from the PARTNERS
(Pan-Arctic River Transport of Nutrients, Organic Matter, and Suspended Sediments) Project with a regionally configured version
of the MIT general circulation model to develop estimates of the distribution and availability of dissolved riverine N in
the Arctic Ocean, assess its importance for primary production, and compare these estimates to potential bacterial production
fueled by riverine C. Because riverine dissolved organic nitrogen is remineralized slowly, riverine N is available for uptake
well into the open ocean. Despite this, we estimate that even when recycling is considered, riverine N may support 0.5–1.5 Tmol C year−1 of primary production, a small proportion of total Arctic Ocean photosynthesis. Rapid uptake of dissolved inorganic nitrogen
coupled with relatively high rates of dissolved organic nitrogen regeneration in N-limited nearshore regions, however, leads
to potential localized rates of riverine-supported photosynthesis that represent a substantial proportion of nearshore production. 相似文献