Testing optically stimulated luminescence dating on sand-sized quartz of deltaic deposits from the Sperchios delta plain,central Greece

This study reports on the first investigation into the potential of luminescence dating to establish a chronological framework for the depositional sequences of the Sperchios delta plain, central Greece. A series of three borehole cores(20 m deep) and two shallow cores(4 m deep), from across the delta plain, were extracted, and samples were collected for luminescence dating. The luminescence ages of sand-sized quartz grains were obtained from small aliquots of quartz, using the Single-Aliquot Regenerative-dose(SAR) protocol.The equivalent dose determination included a series of tests and the selection of the Minimum Age Model(MAM) as the most appropriate statistical model. This made it possible to confirm the applicability of quartz Optically Stimulated Luminescence(OSL) dating to establish absolute chronology for deltaic sediments from the Sperchios delta plain.Testing age results of the five cores showed that the deltaic sediments were deposited during the Holocene.A relatively rapid deposition is implied for the top ~14 m possibly as a result of the deceleration in the rate of the sea-level rise and the transition to terrestrial conditions, while on the deeper parts, the reduced sedimentation rate may indicate a lagoonal or coastal environment.     

Dynamically equivalent rocking structures

Predicting the rocking response of structures to ground motion is important for assessment of existing structures, which may be vulnerable to uplift and overturning, as well as for designs which employ rocking as a means of seismic isolation. However, the majority of studies utilize a single rocking block to characterize rocking motion. In this paper, a methodology is proposed to derive equivalence between the single rocking block and various rocking mechanisms, yielding a set of fundamental rocking parameters. Specific structures that have exact dynamic equivalence with a single rocking block, are first reviewed. Subsequently, approximate equivalence between single and multiple block mechanisms is achieved through local linearization of the relevant equations of motion. The approximation error associated with linearization is quantified for three essential mechanisms, providing a measure of the confidence with which the proposed methodology can be applied. Copyright © 2014 John Wiley & Sons, Ltd.     

The structure of Neptune's upper atmosphere: The stellar occultation of 24 May 1981

Observations of the 24 May 1981 occultation of an uncatalogued star by Neptune made at the Cerro Tololo Inter-American Observatory have been analyzed to yield temperature profiles of Neptune's upper atmosphere for number densities near 5 × 10¹³ cm^?3. The mean temperatures at immersion (latitude ?56°) and emersion (latitude ?16°) obtained by numerical inversion were 140 ± 10°K and 154 ± 10°K, respectively. The immersion and emersion profiles are remarkably similar in overall shape, suggestive of global atmospheric layering. From the astrometry of the event, precise relative positions of Neptune and the occulted were obtained.     

The ISM in nearby galaxies

The SKA will revolutionise the study of the principles underlying star formation (SF), resolving interstellar cloud complexes which are the birthplaces of stars and answering such questions as which are the sufficient and necessary conditions for SF to commence. Also, massive SF is intimately related to stellar death. The SKA will be able to study the structure of the ISM at 100 pc resolution out to distances of up to 20 Mpc and will quantify the impact the demise of massive stars has on their environment. Importantly, the SKA will probe the transition region between ISM and IGM, linking star formation and stellar death in the disks of galaxies to faint HI structures further afield, such as “anomalous gas” and (Compact) High Velocity Clouds. Lastly, the superb sensitivity of the SKA will result in some hundred background sources per square degree against which HI absorption lines can be searched for, probing not only the relative importance of the different phases of the gas in galaxies but also the low density gas in the outskirts and between galaxies.     

Hierarchical star formation: stars and stellar clusters in the Gould Belt

We perform a study of the spatial and kinematical distribution of young open clusters in the solar neighbourhood, discerning between bound clusters and transient stellar condensations within our sample. Then, we discriminate between Gould Belt (GB) and local Galactic disc (LGD) members, using our previous estimate of the structural parameters of both systems obtained from a sample of O-B6 Hipparcos stars. Single membership probabilities of the clusters are also calculated in the separation process. Using this classified sample, we analyse the spatial structure and the kinematic behaviour of the cluster system in the GB. The two star formation regions that dominate and give the GB its characteristic-inclined shape show a striking difference in their content of star clusters: while Ori OB1 is richly populated by open clusters, not a single one can be found within the boundaries of Sco OB2. This is mirrored in the velocity space, translating again into an abundance of clusters in the region of the kinematic space populated by the members of Ori OB1, and a marginal number of them associated with Sco OB2. We interpret all these differences by characterizing the Orion region as a cluster complex typically surrounded by a stellar halo, and the Sco-Cen region as an OB association in the outskirts of the complex. In the light of these results, we study the nature of the GB with respect to the optical segment of the Orion Arm, and we propose that the different content of star clusters, the different heights over the Galactic plane and the different residual velocities of Ori OB1 and Sco OB2 can be explained in terms of their relative position to the density maximum of the Local Arm in the solar neighbourhood. Although morphologically intriguing, the GB appears to be the result of our local and biased view of a larger star cluster complex in the Local Arm, that could be explained by the internal dynamics of the Galactic disc.     

Non-minimal coupling of the phantom field and cosmic acceleration

Motivated by the recent interest in phantom fields as candidates for the dark energy component, we investigate the consequences of the phantom field when is minimally coupled to gravity. In particular, the necessary (but insufficient) conditions for the acceleration and superacceleration of the universe are obtained when the non-minimal coupling term is taken into account. Furthermore, the necessary condition for the cosmic acceleration is derived when the phantom field is non-minimally coupled to gravity and baryonic matter is included.     

The use of press data in the development of a database for rainfall-induced landslides in Tegucigalpa,Honduras, 1980–2005

The capital city of Honduras, Tegucigalpa, suffers from the occurrence of destructive landslides on a yearly basis. During the rainy season, damages to infrastructure as well as injuries, casualties and homeless individuals resulting from landslides are reported in the press. This paper presents the development of a database for rainfall-induced landslides for the period 1980–2005, based on the news reported by two local newspapers. The editions comprehended during the study period have been scrutinized, and articles focusing on landslides, tropical storms, hurricanes, floods and vulnerability of the city have been collected. The interpretation of these archives has allowed the compilation of valuable data of approximately 400 landslides. The analyses of monthly and annual precipitation during the study period show how extreme rainfall events like Hurricane Mitch in October of 1998 have significantly contributed to the initiation of landslides. In addition, the assessment of the slums and neighborhoods affected by landslides during the study period reveals an evident link between the social and physical vulnerability of Tegucigalpa. In order to estimate the reliability of this press-based database, the set of landslides that have been reported as a result of Hurricane Mitch in the press archives has been compared with two inventories based on the interpretation of aerial photographs taken in 1999 and 2001. It is shown that the analysis of the landslide damage left after the hurricane can be enriched with the detailed temporal data provided in the archives and the precise location of these events determined by the aerial photographs. Despite the difficulties faced in the compilation of this database, a good comprehension of the temporal and spatial distribution of landslides in Tegucigalpa has been achieved.     

The practice of Integrated Water Resources Management in South Africa: challenges of women in water user associations

South Africa’s National Water Act and National Water Resource Strategy set out an ambitious societal vision with a strong focus on the redistribution of water resources towards the marginalised and on empowering historically disadvantaged communities including women. This vision is reflected in the framework for Integrated Water Resources Management (IWRM) that acknowledges women as pivotal in water management practices. Based on this premise, this paper examines the challenges women face in performing their roles in IWRM in rural South Africa. It draws on a study of a water user association that operates in the Limpopo Province of South Africa. The design of the study was qualitative in nature with a semi-structured interview as the main data collection tool. The interview involved 14 respondents from Limpopo. The results showed marked gender difference in terms of roles performed. Based on the study, three kinds of roles were revealed: domestic, productive and decision-making roles. Men were significantly involved in productive roles, giving low priority to domestic roles. The key factors found to affect the role of women in decision-making in IWRM were cultural practices, low self-confidence, low levels of capacity, and high workloads. These factors were identified as key institutional inherent within the specific society. As such, these findings have significant implications for the efforts aimed at promoting gender equality. Particularly, the impact of culture on women in water management raises concerns regarding gender issues in rural and remote areas where people are poorer and more culturally conservative.     

A novel index of susceptibility of rivers and their catchments to acidification in regions subject to a maritime influence

A simple, unifying approach to classifying quantitatively the susceptibility of catchment soils and surface waters to acidification is suggested. In areas subject to a strong maritime influence, such as the UK and substantial parts of NW Europe, wherever soil mineral weathering rates are low and soils are unfertilised, atmospherically derived base cations of maritime origins have a greater effect than those derived from biogeochemical weathering on the exchangeable soil base cations. This is directly reflected in the relative base cation concentrations of the associated drainage waters, which become increasingly Na-dominated. Using 10 sub-catchments of the River Dee in north-eastern Scotland, it is shown here that the extent of Na dominance, the ratio of Na⁺ to ΣNa⁺+Ca²⁺+Mg²⁺, at any point in a river provides a quantitative index of the upstream weathering rate and thus of the susceptibility of the river concerned to acidification under diverse flow conditions. Data from a further 58 sub-catchments from the same river system, and from 4 other catchments from around Scotland, were used to validate this theory.