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21.
The live reef food fish (LRFF) trade has an estimated annual retail value of US$1 billion in the Asia-Pacific region and at least US$30 million in the Philippines. Palawan Province is the trade's center accounting for as much as 55% of the commodity's total export. Concern about the LRFF trade has caused the Palawan Provincial government to take action to regulate the trade. Four key policy options to address the short-term policy objective of developing a sustainable LRFF industry through the reduction of threats associated with destructive fishing and overfishing were proposed. These four policy options and associated analyses were presented to stakeholders at three separate policy consultations. The stakeholders reached a consensus that a regulated LRFF trade was the most sensible option. As a result, the Provincial Government of Palawan took action to enact “The Palawan Live Reef Fish Ordinance of 2006”, which provides for the sustainable and integrated regulation of the LRFF industry. This provincial ordinance will assist in crafting a national policy for the LRFF trade and may also be useful in revising the 1998 Philippine Fisheries Code. The key challenge is how to translate the ordinance provisions into effective on-the-ground actions.  相似文献   
22.
Up to 10 m in length and >1 m in diameter tubular, calcite-cemented sandstone concretions are hosted by the faulted Dikilitash unconsolidated sands and sandstones. These structures document shallow subsurface pathways of Early Eocene methane seepage in the Balkan Mountains foreland (NE Bulgaria). Their exceptional exposure allowed a unique study of the factors governing the morphology and spatial distribution of such fossilized fluid conduits. The large dimensions and subvertical, cylindrical shape of the most common tube type primarily reflects the buoyancy-driven, vertical path of an ascending gas-bearing fluid through permeable, mainly unconsolidated sandy host sediments. Tube morphology was also influenced by local stratigraphic anisotropies and might as well document differences in former seepage conditions. Mapping of >800 tubular concretions showed the NNW–NNE elongation and alignment of tube clusters and massive cemented sandstone structures. This suggests that Paleogene fault systems played a major role in directing the movement of fluids. However, within a single tube cluster, tubes are preferentially aligned, over distances up to 50 m along directions at an angle between 10° and 36° with respect to the inferred NNW–NNE, cluster parallel fault traces. In addition, cylindrical tubes of analogue dimensions are aligned over distances >100 m along N15° to N25°-oriented directions. It is hypothesized that this spatial geometry of tubular concretions reflects the complex geometry of deformations structures in fault damage zones along which fluids were preferentially channelled.  相似文献   
23.
The aim of the time distribution methodology presented in this paper is to generate constellations whose satellites share a set of relative trajectories in a given time, and maintain that property over time without orbit corrections. The model takes into account a series of orbital perturbations such as the gravitational potential of the Earth, the atmospheric drag, the Sun and the Moon as disturbing third bodies and the solar radiation pressure. These perturbations are included in the design process of the constellation. Moreover, the whole methodology allows to design constellations with multiple relative trajectories that can be distributed in a minimum number of inertial orbits.  相似文献   
24.
Hypervelocity collisions of solid bodies occur frequently in the solar system and affect rocks by shock waves and dynamic loading. A range of shock metamorphic effects and high‐pressure polymorphs in rock‐forming minerals are known from meteorites and terrestrial impact craters. Here, we investigate the formation of high‐pressure polymorphs of α‐quartz under dynamic and nonhydrostatic conditions and compare these disequilibrium states with those predicted by phase diagrams derived from static experiments under equilibrium conditions. We create highly dynamic conditions utilizing a mDAC and study the phase transformations in α‐quartz in situ by synchrotron powder X‐ray diffraction. Phase transitions of α‐quartz are studied at pressures up to 66.1 and different loading rates. At compression rates between 0.14 and 1.96 GPa s?1, experiments reveal that α‐quartz is amorphized and partially converted to stishovite between 20.7 GPa and 28.0 GPa. Therefore, coesite is not formed as would be expected from equilibrium conditions. With the increasing compression rate, a slight increase in the transition pressure occurs. The experiments show that dynamic compression causes an instantaneous formation of structures consisting only of SiO6 octahedra rather than the rearrangement of the SiO4 tetrahedra to form a coesite. Although shock compression rates are orders of magnitude faster, a similar mechanism could operate in impact events.  相似文献   
25.
26.
Introduction     
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27.
The Northern Apennines have been subdivided into homogeneous zones, on the basis of recent structural evolution and crustal structure, in which the earthquake distribution can find a coherent framework. These zones, whose physiography is in strict connection with their structure, are: the Internal Peri-Tyrrhenian Belt; the External or Main Belt; the Buried Belt; and the Pede-Alpine Homocline. Earthquake activity has a tendency to cluster along well-defined bands, particularly in the easternmost border of the Peri-Tyrrhenian Belt, as well as along the zone between the External Belt and the Buried Belt, i.e. along the Padanian margin of the Northern Apennines.A minimum of seismic activity seems to be correlated with some zones of the External Belt, as well as with the Late Tertiary and Quaternary magmatic province of Tyrrhenian Southern Tuscany.The fault-plane solutions are coherent with the structural picture.A tentative seismotectonic model of the Northern Apennines is discussed.  相似文献   
28.
Summary A model of a building cumulus structure is described. The one-stage model published in[1] was used to describe ascent of two cloudy parcels that a cloud is supposed to be formed of. The other ascent is assumed to take place after the first cloud element sinks back as a result of evaporative cooling. The numerical results and their evaluation are given for various rates of mixing at the cloud top level of the first cloud volume.  相似文献   
29.
Eva Falck 《Polar research》2001,20(2):193-200
Measurements of nitrate and phosphate taken in the Northeast Water Polynya (NEWP) during the summer of 1993 have been used to identify the contribution of waters of Atlantic and Pacific origin in the polynya. Since waters from the northern Pacific exhibit a deficit in nitrate relative to phosphate due to denitrification in low oxygen waters, the relationship between nitrate and phosphate can be used to distinguish between oceanic waters of Pacific and Atlantic origin. The Pacific Water enters the Arctic Ocean through Bering Strait and flows along the northern coasts of Alaska and Canada. Some of this water exits through Fram Strait and may therefore enter the polynya which is situated above the continental shelf off the north-eastern coast of Greenland. Compared to data from the Greenland Sea, which only show a N–P relationship of typical Atlantic Water, the data from the Northeast Water Polynya show that the upper waters of the polynya bear a clear signal of waters of Pacific origin. In the surface mixed layer an average of about 90% is found to have Pacific N–P characteristics. Below the surface mixed layer the amount of Pacific derived water decreases through the halocline and from about 150 m to the bottom only typical Atlantic Water is found.  相似文献   
30.
Fabrizio Eva 《GeoJournal》2001,52(4):295-301
Discussion of the future of Europe continues to be a marginal political issue, partly because of the resistance of states, on both the practical (bureaucratic) and conceptual levels, created by the government leaders and heads of state. In turn, the nation-states are challenged from within by independent and separatist movements that have laid bare the fundamental hypocrisy of rhetorical discussions of the principle regarding the self-determination of peoples; interfering with states (and their borders) has proven to be a taboo for Europe. The growing flexibility of the globalised economy should be paralleled by a growing flexibility in the conception of the division and political organisation of territory, but this is not the case. Further inflexibility stems from the socio-economic inequity that we accept in our daily lives as normal, in particular as regards inequality in the use and division of territory. Equality, or better egaliberté (equality and liberty), is a sufficiently dynamic and flexible concept to be taken as a point of reference in envisaging the society, Europe, and world of tomorrow. It is only through the concept of egaliberté that we can imagine a Europe based on relations between regions that are conceived and organised on multiple scales and not as region-nations conceived on the basis of ethnicity or in the name of supposed cultural homogeneity.  相似文献   
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