Interannual variability of wave climate in the Caribbean Sea

Ocean Dynamics - Low-frequency interannual climatic oscillations have been reported to influence the precipitation regimes, river discharges, winds, and sea level in the Caribbean Sea. Here, we...     

Human exclusion from rocky shores in a mediterranean marine protected area (MPA): an opportunity to investigate the effects of trampling

The effect of human trampling on the abundance of small invertebrates inhabiting rocky shallow bottoms was studied at Asinara Island MPA. To this aim we have conducted two experiments. The first was a quantitative study and tested the hypothesis that small invertebrates are more abundant at no-entry locations than at the location visited by tourists through time (before, during and after tourist season). The second was a manipulative experiment and tested the hypothesis that the abundance of small invertebrates is indirectly related to experimental trampling intensities. The effect due to tourist visitation was not highlighted on overall assemblages, suggesting that present seasonal tourist load at the MPA does not cause a significantly negative effect on the zoobenthic community studied. Although tourists exhibited trampling activity at the visited location, none of taxa examined showed a significant lower abundance during and strictly after the end of seasonal tourism peak in the visited location, rather than at control locations. However, results obtained with the second experiment suggested that the effects of different experimental trampling intensities on small invertebrates were variable among taxa. The experimental trampling caused immediate declines in the density of tanaids, nematodes, acari, bivalves, gammarids, echinoderms, isopods, and harpacticoids. For some of these taxa a recovery in abundance was observed within one month. This kind of data may offer important information to estimate the number of visitors compatible with the sensitivity of zoobenthic assemblages, and may substantially contribute to appropriate MPA management.     

Measurements of the 44-μm band of H2O ice deposited on amorphous carbon and amorphous silicate substrates

We present 20–110 µm absorbance spectra of H₂O ice, deposited on amorphous carbon and silicate substrates, obtained over the 10–140 K temperature range. The measurements have been carried out in a manner that simulates the deposition, warming and cooling of H₂O ice mantles on interstellar and circumstellar grains. For H₂O ice films deposited on these substrates we find (i) similar 44-µm-band peak wavelength temperature dependences, (ii) no bandshape differences in the respective spectra, and (iii) a structural phase transition occurring between 120 and 130 K. In comparison with published data obtained using a polyethylene substrate, the 52-µm feature (the longitudinal optical mode) observed in our spectra is less prominent. This suggests the presence of material-dependent substrate effects that can alter the appearance of the H₂O far-infrared spectrum. The crystallization temperature of H₂O ice films deposited on our amorphous silicate substrate is significantly different from that reported by Moore et al. (1994) , who found crystallization temperatures down to < 20 K for ice also deposited on an amorphous silicate substrate. This is attributed to differences in the surface structures of the respective substrates. This may indicate that, at least in the context of laboratory measurements, substrate material composition is not as significant as substrate surface structure.     

Indentation of a continent with a built-in thickness change: experiment and nature

Orogens oblique to the direction of plate convergence are currently attributed to obliquity between the margins of one or both of the sutured continents to their direction convergence. We use a single analogue experiment and natural examples to illustrate a potential additional factor: variations in strength of the indented continent at a high angle to the convergence direction. The wavelengths of structures in laterally shortened lithosphere depend on the strength of the most competent layers. Lateral variations in crustal thickness must therefore lead to structures oblique to any applied lateral compression.

An analogue experiment was performed to explore this phenomenon. A two-layer ‘indented continent’ was modelled by a brittle upper crust of sand above a lower crust of high-viscosity polymer floating on a single layer of low-viscosity syrup representing the mantle. The well-known strike-slip structures allowing lateral escape to distant weak boundaries were hindered by lateral boundaries in front of the indenter. This allowed us to focus on the effects of a thickness change built into the ‘indented continent’ along a zone parallel to the direction in which a vertical rigid wall advancing at a steady rate represented the indenter. Vertical escape led to an ‘orogenic belt’ oblique to the advancing wall; this obliquity influences subsequent lateral escape. Model scaling and interpretations are based on Extended Thin Sheet Approximation (ETSA) and standard theories of faulting.

Four sectors of the Alpine–Himalayan orogen (Iran, Tunisia, the Eastern Alps and the Himalaya) are oblique to the continental convergence direction, and we point to thickness changes at high angles to the suture that may account for this geometry. As crustal thicknesses north of oblique sectors of the Himalayas are not yet known, we speculate on them.

We infer from the main difference between our experiment and all our examples chosen from nature that vertical orogenic escape was oblique to our model suture but can be parallel to natural sutures.     

Signs of power: Fascist urban iconographies in Ethiopia (1930s–1940s)

The aim of the present paper is to compare two different patterns of urban iconographies in Ethiopia during 1930s: the one of the Amhara – the traditionally Ethiopian dominant ethnic group – and the one of the Italian fascism. The paper gives an historical account of the structure of the Amhara settlements, focusing on the ways the power of their politico-military chiefs, being they the Negus or the Ras, shaped the spatial order of these settlements. When the Italians conquered military Ethiopia in 1936, they started re-shaping this spatial order, erasing the signs of the previous power and imposing their new iconographic apparatus. This was mainly done through urban planning which was devised to `write' the Fascist concepts of progress, order, hierarchy, and racial segregation on the territory. Owing to the short duration of the occupation, the poor material conditions of the colony and the lack of financial resources, such town-planning projects turned out to be just a political rhetoric exercise.     

1951-2002年长江流域降水特征

The monthly, seasonal, and annual precipitation trends in the Yangtze river catchment have been detected through analysis of 51 meteorological stations‘ data between 1950-2002 provided by National Meteorological Administration. Results reveal that: 1) Summer precipitation in the Yangtze river catchment shows significant increasing tendency. The Poyanghu lake basin, Dongtinghu lake basin and Taihu lake basin in the middle and lower reaches are the places showing significant positive trends. Summer precipitation in the middle and lower reaches experienced an abrupt change in the year 1992; 2) The monthly precipitation in months just adjoining to summer shows decreasing tendency in the Yangtze river catchment. The upper and middle reaches in Jialingjiang river basin and Hanshui river basin are the places showing significant negative trends; 3) Extreme precipitation events show an increasing tendency in most places, especially in the middle and lower reaches of the Yangtze river catchment.     

Computations of radial velocities for O-type stars

From the study of the spectra of eighteen O-type stars can be argued that a large Compton redshift is present, that could be due to the scattering of the light of these stars in the surrounding envelopes of interstellar matter. The new values of radial velocities, obtained for the above-quoted stars by means of a formula which takes into account the generalized Compton effect, are inconsistent with the values given in the stellar catalogue.     

Chemical compositions of impact melt breccias and target rocks from the Tenoumer impact crater,Mauritania

Abstract— The impact melt breccias from the Tenoumer crater (consisting of a fine‐grained intergrowth of plagioclase laths, pyroxene crystals, oxides, and glass) display a wide range of porosity and contain a large amount of target rock clasts. Analyses of major elements in impact melt rocks show lower contents of SiO₂, Al₂O₃, and Na₂O, and higher contents of MgO, Fe₂O₃, and CaO, than the felsic rocks (i.e., granites and gneisses) of the basement. In comparison with the bulk analyses of the impact melt, the glass is strongly enriched in Si‐Al, whereas it is depleted both in Mg and Fe; moreover, the impact melt rocks are variably enriched or depleted in some REE with respect to the felsic and mafic bedrock types. Gold is slightly enriched in the impact melt, and Co, Cr, and Ni abundances are possibly due to a contribution from mafic bedrock. Evidences of silicate‐carbonate liquid immiscibility, mainly as spherules and globules of calcite within the silicate glass, have been highlighted. HMX mixing calculation confirm that the impact melt rocks are derived from a mixing of at least six different target lithologies outcropping in the area of the crater. A large contribution is derived from granitoids (50%) and mica schist (17–19%), although amphibolites (?15%), cherty limestones (?10%), and ultrabasites (?6%) components are also present. The very low abundances of PGE in the melt rock seem to come mainly from some ultrabasic target rocks; therefore, the contamination from the meteoritic projectile appears to have been negligible.     

The generalized compton effect in the spectrum of Deneb

The radial velocity and the redshift caused by the scattering of photons in the chromosphere of Deneb and in the interstellar matter is obtained from the wavelengths and FWHM of about 30 spectral lines measured in two spectra observed in 1979.     

The winds of WC10 central stars of planetary nebulae

We present the results of an analysis of the winds of two WC10 central stars of planetary nebulae, CPD-56°8032 and He 2-113. These two stars have remarkably similar spectra, although the former exhibits somewhat broader emission line widths. High resolution spectra (up to R=50 000) were obtained in May 1993 for both objects at the 3.9 m AAT, using the UCL Echelle Spectrograph. The fluxes in individual Cii auto-ionising multiplet components, many of which were blended, were derived. Lines originating from auto-ionising resonance states situated in the C²⁺ continuum are very sensitive to the electron temperature, since the population of the these levels is close to LTE. The measured widths and profile shapes of these transitions are presented and are in excellent agreement with those predicted on the basis of their calculated auto-ionising lifetimes. The wind electron temperature is derived for both stars from the ratio of the fluxes in four such transitions (T _e =18 500 K±1 500 K for CPD-56° 8032 andT _e =13 600 K±800 K for He 2-113). Optical depth effects are investigated using normal recombination lines to obtain an independent wind electron temperature estimate in excellent agreement with the dielectronic line analysis.