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91.
The relative performance of (i) percent live cover, (ii) colony density, (iii) generic richness, (iv) partial colony mortality, and (v) colony size of hard corals were evaluated to determine which variables best discriminated the coral communities near a small river in Okinawa, Japan. An analysis of their variance was undertaken across a combination of sites at three depths, at increasing distance from a river's influence (Zatsun River). The river provides a periodic and localized input of sediment and fresh water to the adjacent coral reef; the effects of which we assume attenuate at increasing distance from the river mouth. The mean frequency of partially dead coral colonies (i.e., the proportion of live coral colonies that were partially dead) presented the clearest and most reliable response to river affect, and the power to discriminate among sites improved steadily with increasing depth. Spatial examination of the prevalence of partial mortality, regardless of how long ago the infliction occurred, provides a clear window to long-term processes involving population and community change and indeed the reef building capacity of the communities.  相似文献   
92.
The GAUGE (GrAnd Unification and Gravity Explorer) mission proposes to use a drag-free spacecraft platform onto which a number of experiments are attached. They are designed to address a number of key issues at the interface between gravity and unification with the other forces of nature. The equivalence principle is to be probed with both a high-precision test using classical macroscopic test bodies, and, to lower precision, using microscopic test bodies via cold-atom interferometry. These two equivalence principle tests will explore string-dilaton theories and the effect of space–time fluctuations respectively. The macroscopic test bodies will also be used for intermediate-range inverse-square law and an axion-like spin-coupling search. The microscopic test bodies offer the prospect of extending the range of tests to also include short-range inverse-square law and spin-coupling measurements as well as looking for evidence of quantum decoherence due to space–time fluctuations at the Planck scale.  相似文献   
93.
A compressional study of (Na,Ca)(Ti3+,Mg)Si2O6-clinopyroxenes was carried out at high pressures between 10−4 and 10.2 GPa using in situ single-crystal X-ray diffraction, Raman spectroscopy and optical absorption spectroscopy. Compressional discontinuities accompanied by structural changes, in particular, the appearance of two distinct Ti3+–Ti3+ distances within the octahedral chains at 4.37 GPa, provide evidence for the occurrence of a phase transition in NaTi3+Si2O6. Equation-of-state parameters are K 0 = 115.9(7) GPa with K′ = −0.9(3) and K 0 = 102.7(8) GPa with K′ = 4.08(5) for the low- and high-pressure range, respectively. The transition involves a C2/c–P [`1] \overline{1} symmetry change, which can be confirmed by the occurrence of new modes in Raman spectra. Since no significant discontinuity in the evolution of the unit-cell volume with pressure has been observed, the transition appears to be second-order in character. The influence of the coupled substitution Na+Ti3+↔Ca2+Mg2+ on the static compression behavior and the structural stability has been investigated using a sample of the intermediate composition (Na0.54Ca0.46)(Mg0.46Ti0.54)Si2O6. No evidence for a deviation from continuous compression behavior has been found, neither in lattice parameter nor in structural data and the fit of a third-order Birch–Murnaghan equation-of-state to the pressure–volume data yields a bulk modulus of K 0 = 109.1(5) GPa and K′ = 5.02(13). Raman and polarized absorption spectra have been compared to NaTiSi2O6 and reveal major similarities. The main driving force for the phase transition in NaTi3+Si2O6 is the localization of the Ti3+ d-electron and the accompanying distortion, which is suppressed in the (Na,Ca)(Ti3+,Mg)Si2O6-clinopyroxene.  相似文献   
94.
Microprobe analysis, single crystal X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy, and X-ray absorption spectroscopy were applied on Fe-rich osumilite from the volcanic massif of Mt. Arci, Sardinia, Italy. Osumilite belongs to the space group P6/mcc with unit cell parameters a = 10.1550(6), c = 14.306(1) Å and chemical formula (K0.729)C (Na0.029)B (Si10.498 Al1.502)T1 (Al2.706 Fe 0.294 2+ )T2 (Mg0.735 Mn0.091 Fe 1.184 2+ )AO30. Structure refinement converged at R = 0.0201. Unit cell parameter a is related to octahedral edge length as well as to Fe2+ content, unlike the c parameter which does not seem to be affected by chemical composition. The determination of the amount of each element on the mineral surface, obtained through X-ray photoelectron spectroscopy high-resolution spectra in the region of the Si2p, Al2p, Mg1s and Fe2p core levels, suggests that Fe presents Fe2+ oxidation state and octahedral coordination. Two peaks at 103.1 and 100.6 eV can be related to Si4+ and Si1+ components, respectively, both in tetrahedral coordination. The binding energy of Al2p, at 74.5 eV, indicates that Al is mostly present in the distorted T2 site, whereas the Mg peak at 1,305.2 eV suggests that this cation is located at the octahedral site. X-ray absorption at the Fe L2,3-edges confirms that iron is present in the mineral structure, prevalently in the divalent state and at the A octahedral site.  相似文献   
95.
ABSTRACT

Growth in water use and threatened shortages of water have become increasingly important in the modern world system. Natural resources are exploited extensively by capitalist interests in industrially advanced nations, while the lower strata of the world system, the underdeveloped societies, are left with limited access to natural resources for their productive processes, particularly water resources. We contribute to socio-hydrological research by examining underlying socio-structural factors that play a part in the process of deteriorating conditions of global water resources. Drawing on a world-systems perspective, this study examines how socio-structural forces – world-system position, per capita beef consumption, per capita energy consumption, and urbanization – affect per capita water footprint, which includes an accounting of “virtual water” consumption. We find that per capita beef consumption and per capita energy consumption have significant positive direct effects, and the world-system position has a significant indirect and total effect on per capita water footprint.  相似文献   
96.
A grid-based technique for mapping potential evapotranspiration is described. An attempt is made to extrapolate the constituent parameters of Penman's equation (1962) over a grid, so that the equation can be evaluated for every grid square. Data for a part of Southwest England are used to demonstrate the technique. Aspect and slope, which determine evaporation to a considerable degree, have been included using a formula derived by Okanoue.  相似文献   
97.
Iron is the most abundant transition metal in the atmosphere and can play a significant role in cloudwater chemistry where its reactivity is closely related to the partitioning between Fe(II) and Fe(III). The objective of this work is to determine the total iron content and the iron speciation in a free tropospheric site, and to understand which factors influence these parameters. We collected 147 samples of cloudwater during 34 cloud events over a period of four years at the puy de Dôme summit. Besides iron we measured other chemical compounds, solar radiation, physico-chemical and meteorological parameters potentially connected with iron reactivity. The total iron concentrations ranged from 0.1 to 9.1 μM with the major frequency occurring at low levels. The pH and presence of organic complexants seem to be the most significant factors connected with total dissolved iron; while the iron oxidation state seems to be an independent factor. Light intensity, presence of complexants or oxidants (H2O2) do not influence the Fe(II)/Fe(Total) ratio, that was quite constant at about 0.75. This could be due to the potential redox that forces the Fe(II)-Fe(III) couple to the reduced form or, more probably to the complexation by Natural Organic Matter, that can stabilize iron in its reduced form and prevent further oxidation. Our field measurements did not show the diurnal cycle observed in surface water and predicted by models of atmospheric chemistry. This result prompts a more careful review of the role of iron and, by analogy, all the transition metals in atmospheric liquid phase, often over-estimated in the literature.  相似文献   
98.
99.
We present a 2.2-μm polarization image of the nuclear regions of Cygnus A. The degree of polarization in the central 1 arcsec is (4.1±0.50) per cent, at a position angle of (23.6±3.6)°, approximately perpendicular to the axis of the radio jet.
Modelling of the results suggests that at this wavelength the polarization along the line of sight to the central source is most likely produced by dichroism, through an A v∼40 mag, with the polarization in surrounding regions produced by scattering. For this model, the K -band luminosity of the central source is calculated to be ∼2×1044 erg s−1.  相似文献   
100.
Animal bones, associated with Palaeolithic artefacts and skeletal remains of early hominids from the cave of La Chaise-de-Vouthon, have been dated using a new approach to uranium series dating of bone. Speleothem (cave calcite) interstratified with bone-bearing sediments in the two chambers of Grotte Bourgeois-Delaunay and Grotte Suard have previously been dated by the 230Th/234 U method. This provides a chronological control for the bone ages, for which the method is still at an experimental stage. A good agreement is shown in most cases between the calcite and the bone ages, showing the cave to have been a stable environment for the deposition of bone and the acquisition of uranium.  相似文献   
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