The Response of Estuarine Macrobenthic Communities to Natural- and Human-Induced Changes: Dynamics and Ecological Quality

Anthropogenic activities are a disturbance factor of coastal systems and can be widely recognized as a major threat to the health of coastal systems. However, natural events cannot be disregarded from management issues because of their significant influence on the communities living in these areas. Based on long-term subtidal data from the Mondego Estuary (Portugal), the effects of natural events (e.g., floods and droughts) on macrobenthic communities were compared with the anthropogenic events. Sampling stations were grouped into characteristic zones (mouth, north arm, south arm) so the community dynamics of each of these estuarine areas could be followed over time. Environmental assessment was performed for stations using the Benthic Assessment Tool (BAT), and compared with the existing pressures. Human impacts persist over a number of years and gradually reduce ecosystem health, as discussed in the European Water Framework Directive. Paradoxically, natural events cause stronger impacts but are of a shorter duration, which allows for a faster recovery of macrobenthic communities. The study showed that caution should be taken when developing and implementing water policies so as not to disregard the importance of the different events (natural and human-caused) on the ecosystem health (e.g., community degradation and water quality and ecological quality status assessment).     

Bioremediation of dry olive-mill residue removes inhibition of growth induced by this waste in tomato plants

The disposal of dry olive-mill residue, the waste product from olive oil production, is a serious environmental issue. Dry olive-mill residue, being rich in organic and inorganic nutrients, could be used as fertilizer; however, it contains phenolic compounds that can inhibit plant growth. In order to clarify whether bioremediation of this waste could be a valuable strategy for its reuse, the effect of aqueous extract of dry olive-mill residue, untreated or bioremediated by the saprobe fungi Coriolopsis rigida and Penicillium chrysogenum-10, has been analyzed in relation to some physiological parameters of tomato plants. The data show that aqueous dry olive-mill residue significantly reduces the biomass of roots and shoots. In particular, it causes a dramatic reduction in root length, area, and volume as well as in the number of root tips. At an early stage, aqueous dry olive-mill residue also reduces the content of chlorophyll a and b and the efficiency of PS II. The inhibition of growth seems to be due to the increase in phenolic compounds that induce oxidative stress. Interestingly, when plants are treated with aqueous dry olive-mill residue bioremediated by saprobe fungi a decrease in phenolic content and an alleviation of oxidative stress occur. In conclusion, the results show that bioremediation of aqueous dry olive-mill residue is a useful tool to remove most of the inhibiting effects of this waste on plant growth.     

Appraising stone column settlement prediction methods using finite element analyses

Numerous approaches exist for the prediction of the settlement improvement offered by the vibro-replacement technique in weak or marginal soil deposits. The majority of the settlement prediction methods are based on the unit cell assumption, with a small number based on plane strain or homogenisation techniques. In this paper, a comprehensive review and assessment of the more popular settlement prediction methods is carried out with a view to establishing which method(s) is/are in best agreement with finite element predictions from a series of PLAXIS 2D axisymmetric analyses on an end-bearing column. The Hardening Soil Model in PLAXIS 2D has been used to model the behaviour of both the granular column material and the treated soft clay soil. This study has shown that purely elastic settlement prediction methods overestimate the settlement improvement for large modular ratios, while the methods based on elastic–plastic theory are in better agreement with finite element predictions at higher modular ratios. In addition, a parameter sensitivity study has been carried out to establish the influence of a range of different design parameters on predictions obtained using a selection of elastic–plastic methods.     

Influence of size on the constitutive equations of concrete or rock dowels

The numerical fracture analysis of non‐homogeneous rock or concrete dowels subjected to shear and compression is described in detail. The method of analysis allows the consideration of scale and rate effects due to material non‐homogeneity and fracture. The proposed approach is verified by comparing numerical predictions with experimental results reported in the literature for a series of small rock samples, since experimental evidence for large bodies is not yet available (2007). Results generated by Monte Carlo simulation using the so‐called discrete element method to model the dowels suggest that a simple three parameters law can be used to predict the relationship between tangential stress at the base and lateral distortion. It is observed that the larger the size of the cubes, the smaller both the peak tangential stress and the rupture distortion. Size effects are also evaluated in samples with vertical restraint. The influence of loading rate is likewise numerically assessed for two sample sizes. The effect is compatible with experimental evidence available for concrete using small samples. Copyright © 2008 John Wiley & Sons, Ltd.     

Sporadic meteor sources as observed by the Jicamarca high-power large-aperture VHF radar

We present, for the first time, the main sources of sporadic meteors as inferred from meteor-head echoes obtained by a high-power large-aperture radar (HPLAR). Such results have been obtained at the Jicamarca HPLAR (11.95° S, 76.87° W, 1° dip angle). Observations are based on close to 170,000 meteors detected in less than 90 h spread over 14 days, between November 2001 and February 2006. Meteors with solar orbits are observed to come from basically six previously known sources, i.e., North and South Apex, Helion, Anti-Helion, and North and South Toroidal, representing ∼91% of the observations. The other ∼9% represents meteors with observed velocities greater than the Sun's escape velocity at 1 AU, most of them of extra-solar origin. Results are given before and after removing the Earth's velocity and the sources are modeled with two-dimensional Gaussian distributions. In general, our results are in very good agreement with previously known sources reported by Jones and Brown [Jones, J., Brown, P.G., 1993. Mon. Not. R. Astron. Soc. 265, 524-532] using mainly specular meteor radar (SMR) data gathered over many years and different sites. However, we find slightly different locations and widths, that could be explained on the basis of different sensitivities of the two techniques and/or corrections needed to our results. For example, we find that the North and South Apex sources are well defined and composed each of them of two collocated Gaussian distributions, one almost isotropic with ∼10° width and the other very narrow in ecliptic longitude and wide in ecliptic latitude. This is the first time these narrow-width sources are reported. A careful quantitative analysis is needed to be able to compare the strengths of meteor sources as observed with different techniques. We also present speed and initial altitude distributions for selected sources. Using a simple angular sensitivity function of the combined Earth-atmosphere-radar instrument, and an altitude selection criteria, the resulting meteor sources are in better qualitative agreement with the results obtained with SMRs.     

Putative Meteoritic Craters in Río Cuarto (Central Argentina) Interpreted as Eolian Structures

Ten oblong aligned depressions in the Río Cuarto area (provincia de Córdoba, Argentina) were supposed to be the result of very-low-angle Holocene meteoroid impacts. However, we consider that authors that studied the structures did not demonstrated their extraterrestrial origin. We suggest that an eolian origin for the structures of Río Cuarto is more likely. Actually, these landforms integrate large systems of similar deflation/accumulation geoforms aligned according to predominant winds during different periods.     

Raman spectroscopic analysis of cyanobacterial colonization of hydromagnesite, a putative martian extremophile

Raman spectra of an extremophile cyanobacterial colony in hydromagnesite from Lake Salda in Turkey have revealed a biogeological modification which is manifest as aragonite in the stratum associated with the colony. The presence of key spectral biomarkers of organic protectant molecules such as β-carotene and scytonemin indicate that the survival strategy of the cyanobacteria is significantly one of UV-radiation protection. The terrestrial location of this extremophile is worthy of consideration further because of its possible putative link with the “White Rock” formations in Sabaea Terra and Juventae Chasma on Mars.     

Astrometry in the Kerr field inPPN approximation

The equation of motion written down using a metric obtained from the Kerr metric allows us to get both the deflection angle of light ray bending by the gravitational field of the Sun and its corresponding time delay. We reproduce the experimental data of Epstein-Shapiro and also it is in accordance with the theoretical results obtained by Brumberget al. (1990) using another approach to this problem.Presented at the 2nd UN/ESA Workshop, held in Bogotá, Colombia, 9–13 November, 1992.     

Triggering factors,behavior, and social impact of the January 2021 hail-debris flows at the Central Valley of Chile

Landslides - An extreme precipitation event produced catastrophic debris flows in central Chile during 29–31 January 2021 (austral summer). Our study focuses on the triggering factors and...     

Theoretical solution for drained cylindrical cavity expansion in clays with fabric anisotropy and structure

Acta Geotechnica - This paper presents a novel, exact, semi-analytical solution for the quasi-static drained expansion of a cylindrical cavity in soft soils with fabric anisotropy and structure....