Volume diffusion of Ytterbium in YAG: thin-film experiments and combined TEM–RBS analysis

In this study, we address volume diffusion of ytterbium in yttrium aluminum garnet (YAG) using thin-film single crystal diffusion couples. We employ analytical transmission electron microscopy (ATEM) as a tool for combined microstructural and microchemical analysis and compare the results to Rutherford backscattering (RBS) analysis. Given the high spatial resolution of the method, we focus on microstructural changes of the thin-film diffusant source during the diffusion anneal. We evaluate the potential influence of the associated changes in its transport properties on the evolution of concentration profiles in the single crystal substrate. This approach allows us to test the reliability of determination of volume diffusion coefficients from thin-film diffusion experiments. We found that for the chosen experimental setting, the influence of thin-film re-crystallization is small when compared with the experimental uncertainty and good estimates for the volume diffusion coefficients of Yb in YAG can be obtained using standard assumptions. Both Yb-concentration profiles analyzed with ATEM and with RBS give similar results. At 1,450°C and 1 bar, we infer log D _Yb (m²/s) values of −19.37 ± 0.07 (TEM) and −19.84 ± 0.02 (RBS). Although the change in thin-film transport properties associated with successive crystallization during the diffusion anneal does not play a major role for our experimental setup, this effect cannot generally be ignored.     

EMPLOYMENT DATA AND THE CLASSIFICATION OF URBAN SETTLEMENTS

Classifications of urban settlements have traditionally used total employment data in place of basic (export-oriented) employment data. While urban analysis agree upon the superiority of basic employment data for these classifications, usually only total employment data are available. This paper uses the Arizona Community Data Set, a unique survey-generated body of information that describes the major economic characteristics of numerous Southwestern communities and includes both basic and total employment data, to explore the extent to which misclassification results when using total employment data.     

Environmental heterogeneity affects input, storage, and transformation of coarse particulate organic matter in a floodplain mosaic

Quantifying spatial and temporal dynamics of organic matter (OM) is critical both for understanding ecosystem functioning and for predicting impacts of landscape change. To determine the influence of different habitats and coarse particulate OM (CPOM) types upon floodplain OM dynamics, we quantified aerial input, lateral surface transfer, and surface storage of CPOM over an annual cycle on the near-natural floodplain of the River Tagliamento in NE-Italy. Using these data, we modelled floodplain leaf dynamics, taking account of the spatial distribution and hydrologic connectivity of habitats, and using leaf storage as a response variable. Mean aerial CPOM input to the floodplain was similar from riparian forest and islands, but surface transfer was greater from islands, supporting the suggestion that these habitats act as “islands of fertility” along braided rivers. Leaves were the lateral conveyor of energy to more open parts of the floodplain, whereas CPOM was mainly stored as small wood in vegetated islands and riparian forest. Simulating the loss of habitat diversity (islands, ponds) decreased leaf storage on the whole floodplain, on exposed gravel and in large wood accumulations. In contrast, damming (loss of islands, ponds and floods plus floodplain overgrowth) greatly increased storage on exposed gravel. A random shuffle of habitats led to a storage increase on exposed gravel, while that in large wood accumulations and ponds declined. These results disentangle some of the complexities of CPOM dynamics in floodplain ecosystems, illustrate the value of models in understanding ecosystem functioning at a landscape level, and directly inform river management practice.     

Ein Verfahren zur Berechnung von Gezeitenstrom- und Gefällsellipsen

Zusammenfassung Bei der im Folgenden beschriebenen Methode zur Berechnung der Stromellipsenelemente werden die Summen und Differenzen der Hauptachsen bzw. ihrer Richtungen und Phasen als Beträge bzw. Richtungen zweier Vektoren bestimmt. Die Komponenten dieser Vektoren sind wieder Summen und Differenzen von vier Konstanten, die man bei der harmonischen Analyse der Stromkomponenten bezüglich der betreffenden Tide gewinnt. Eine andere Berechnungsmethode geht von den harmonischen Konstanten der Stromkomponenten aus und benutzt trigonometrische Funktionen komplexen Arguments. Zum Schluß werden Beziehungen zwischen den Elementen der Stromellipse und denen der Gefällsellipse aufgestellt unter der Voraussetzung, daß der Zusammenhang zwischen horizontalen und vertikalen Gezeiten sich durch die linearisierten hydrodynamischen Grundgleichungen darstellen läßt.

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A method of calculating tidal stream and gradient ellipses

Summary In the following paper a method of calculating the elements of tidal stream ellipses is described by which the sums and differences of the major axes or their directions and phases are determined as the scalar quantities or directions of two vectors. The components of these vectors, on their turn, are sums and differences of four constants obtained by the harmonic analysis of the stream components with regard to the respective tide. Another calculating method proceeds from the harmonic constants of the stream components and employs trigonometric functions of complex arguments. Finally, on the supposition that the relation between horizontal and vertical tides may be represented by the linearized fundamental hydrodynamic equations, relations are established between the elements of the tidal stream ellipse and those of the gradient ellipse.

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Mode de calcul des ellipses du courant de marée et du gradient

Résumé Le mode de calcul des éléments des ellipses du courant expliqué ci-dessous demande que les sommes et les différences des grandaxes ou leurs directions et leurs phases soient déterminées comme grandeurs scalaires ou comme directions de deux vecteurs. Les composantes de ces vecteurs sont, de leur part, les sommes ou les différences de quatre constantes qui résultent de l'analyse harmonique des composantes de courant de la marée en question. Une autre méthode de calcul part des constantes harmoniques des composantes de courant et emploie des fonctions trigonométriques à l'argument complexe. Enfin, pourvu que la relation entre les composantes horizontales et verticales puisse être représentée à l'aide des équations hydrodynamiques fondamentales linéarisées, des relations entre les éléments de l'ellipse du courant et ceux de l'ellipse du gradient sont établies.

     

Contrast in life histories of exploited fishes and ecosystem structures in coastal waters off west Canada and east Korea

By reviewing the history of fishery exploitation in the coastal waters of west Canada and east Korea, related with contrasting life history strategies of the dominant species, the fishery management challenges that each country would face in the upcoming decades were outlined. In the ecosystem of the Canadian western coastal waters, the dominant oceanographic feature is the coastal upwelling domain off the west coast of Vancouver Island, the northernmost extent of the California Current System in the eastern North Pacific. In the marine ecosystem of the eastern coasts of Korea (the Japan/East Sea), a major oceanographic feature is the Tsushima Warm Current, a branch of the Kuroshio Current in the western North Pacific. Fishes in the Canadian ecosystem are dominated by demersal, long-lived species such as flatfish, rockfish, sablefish, and halibut. During summer, migratory pelagic species such as Pacific hake, Pacific salmon, and recently Pacific sardine, move into this area to feed. In the late 1970s, Canada declared jurisdiction for 200 miles from their coastline, and major fisheries species in Canadian waters have been managed with a quota system. The overall fishing intensity off the west coast of Vancouver Island has been relatively moderate compared to Korean waters. Fishes in the ecosystem of the eastern Korean waters are dominated by short-lived pelagic and demersal fish. Historically, Korea has shared marine resources in this area with neighbouring countries, but stock assessments and quotas have only recently (since the late-1990s) been implemented for some major species. In the Korean ecosystem, fisheries can be described as intensive, and many stocks have been rated as overfished. The two ecosystems responded differently to climate impacts such as regime shifts under different exploitation histories. In the future, both countries will face the challenge of global warming and subsequent impacts on ecosystems, necessitating developing adaptive fisheries management plans. The challenges will be contrasting for the two countries: Canada will need to conserve fish populations, while Korea will need to focus on rebuilding depleted fish populations.     

旋转流体物理实验中见到的大气环流特征

在合适的实验参数下(热力Rossby数R_(OT)=0.1,Taylor数T_a=2.2 ×10~7),在旋转斜压流中,大尺度地形强迫造成低频振荡以及大气环流中的“阻塞”流型。这是由于地形强迫造成的准静止波与行进波的相互作用及共振引起的。地形把波数单一的流动变成多波数的流动。地形强迫使波数减少。     

Major-element composition of the particulate matter in the near-bottom nepheloid layer of the gulf of Mexico

During cruises 71-A-12 and 73-A-3 of the R/V “Alaminos” eighty-six samples of suspended matter at eleven near-bottom stations in the Gulf of Mexico and northwestern Caribbean Sea were collected, and simultaneously, values for light scattering were measured. Selected samples of the suspended matter were analyzed for particulate aluminum, silicon, iron, calcium, magnesium, organic carbon and inorganic carbon. The results indicate that a permanent but highly variable near-bottom nepheloid layer exists in the Gulf of Mexico but not in the northwestern Caribbean Sea. Average total-suspended loads in the Gulf of Mexico nepheloid layer are two times higher than in the clear water above the nepheloid layer.Since there is a significant increase in the alumino-silicate fraction and a corresponding decrease in the organic fraction of the suspended matter in the nepheloid layer relative to the overlying water, it appears that sediments are the most probable source of the increased concentrations of suspended matter in the nepheloid layer. This hypothesis is supported by X-ray diffraction analyses on the nepheloid material collected at one station which show the same mineral assemblages as the underlying sediments.Time studies over periods of one week and one and one-half years showed large total-suspended-matter variations which indicate that non steady-state processes, primarily vertical eddy diffusion and possibly advection, are controlling the distribution of suspended matter in the nepheloid layer.     

洋面冷锋的三维数值模拟──潜热释放对冷锋结构的影响

通过比较一次洋面冷锋过程的干、湿三维模拟结果，揭示潜热释放对冷锋结构的影响。结果表明：由于潜热释放的作用，冷锋区的温度梯度和风矢量的气旋性切变大大地加强了，冷锋附近的涡度场和垂直速度场呈现出更多的更加紧密的中尺度结构；锋面非地转直接环流在湿模拟中比在干模拟中发展得更加充分并且具有更高的组织性；潜热加热倾向于增加锋面环流的强度，尤其是其上升支的强度。研究表明，潜热释放过程是形成冷锋前沿上方低层大气中狭窄强上升气流区的关键因素之一。