Seismic settlement of a strip foundation resting on a dry sand

Natural Hazards - Seismic settlement of shallow foundations constructed in seismic active areas should be considered for a reasonable estimation of the total settlement. However, the trend of the...     

Addition of Phosphorus and Nitrogen Support the Invasiveness of Alternanthera Philoxeroides Under Water Stress

Coordination of plant functional traits with changes in the environment is helpful to understand the mechanisms underlying both invasiveness and adaptation of plants. Thus, to investigate the performance and functional traits in invasive Alternanthera philoxeroides (Mart.), an experiment of water stress is conducted with different nutrient concentrations. Alternanthera philoxeroides plants are grown under natural and nutrient soils and subjected to three levels of nitrogen (N) and phosphorus (P) solution: ambient P and N concentration (P?N?), P addition with an ambient N concentration (P+N?), and P addition with high N concentration (P+N+) in combination with three different irrigation water levels as 1) 100% irrigation, 2) 50% irrigation, and 3) 25% deficit irrigation. Based on results, A. philoxeroides produces significantly higher biomass in both soils under 100% irrigation with P+N? treatment and exhibits higher values of leaf area and root length. However, 25% irrigation with P?N? treatment in both soils exerts a significant negative effect on relative growth rate and root/shoot ratio of A. philoxeroides plants. Under 50% irrigation in soils with both P+N? and P+N+ treatments, high values of leaf nitrogen are recorded. Moreover, nutrient soil is more supportive to A. philoxeroides than natural soil.     

Effect of turbulence modelling on the computation of the near-wake flow of a circular cylinder

An evaluation of four well-known Reynolds-Averaged Navier-Stokes (RANS)-based turbulence models was performed in comparison with the results of a dedicated experimental measurement on the near-wake of a circular cylinder in a large water (cavitation) tunnel using a state-of-the-art two-dimensional Digital Particle Image Velocimetry (DPIV) device.The turbulence models investigated were Spalart-Allmaras (S-A), Realizable k-ε (RKE), Wilcox k-ω (WKO) and Shear-Stress-Transport k-ω (SST), which were assessed based on their comparative performances in predicting some important flow field characteristics of the near-wake region of the experimental circular cylinder flow. Within the flow range investigated in this study, which implied a cylinder diameter-based Reynolds Number of 41,300, the qualitative and quantitative comparisons revealed that the application of the SST model to the wall-bounded unsteady flow - that experienced severe adverse pressure gradient, massive flow separation and vortex shedding - presents more successful predictions compared to other models investigated for such challenging flow conditions.     

Nagmati River Sub-watershed Prioritization Using PCA,Integrated PCWS,and AHP: A Case Study

Prioritization of potential regions that are severely threatened by soil erosion is a prerequisite for formulating and implementing conservation measures and management practices, particularly in fragile semiarid regions. The present study prioritized eight delineated Nagmati sub-watersheds located in the Kutch District of Gujarat State, India, based on three approaches, namely principal component analysis (PCA), integrated PCA with weighted sum (I-PCWS), and analytical hierarchy process (AHP), and on 10 morphometric erosion risk parameters (ERPs). Sub-watersheds were categorized into three priority classes, namely high, medium, and low. PCA retrieved the three most significant ERPs (i.e., length of overland flow, Lo; drainage texture, Dt; and compactness coefficient, Cc) explaining 86.876% of the variance and exhibiting the highest correlation, i.e., r?=?0.961, 0.986, and 0.934 for the first three principal components. Sub-watersheds SW2 and SW7 were rated high priority, SW1 was rated low priority, and the rest were rated medium priority. The I-PCWS approach revealed that sub-watersheds SW2, SW6, and SW7 were in high-priority zone, followed by SW3, SW4, and SW8 in medium-priority zone and SW1 and SW5 in the low-priority zone. The AHP assigned the highest and lowest ranks to “Lo” and “Cc,” respectively, with consistency ratio of 8.1% and principal eigenvalue of 11.075. Results from AHP revealed sub-watershed SW2 to be the highest priority and sub-watersheds SW1 and SW5 to be the lowest priority. Out of eight prioritized sub-watersheds from three approaches, five were found to be the common priority classes, with SW2, SW6, and SW7 demanding urgent implementation of efficient soil conservation measures to prevent further degradation of the identified regions. Results from I-PCWS approach closely complied with the existing landforms within the study area, and this approach was considered more reliable and robust than the other two approaches. The methodology adopted in this study can be applied to different vulnerable, data-scarce regions to sustainably manage and conserve soil erosion through efficiently framed strategies.

     

Transport and exchange of U-series nuclides between suspended material,dissolved load and colloids in rivers draining basaltic terrains

This study presents uranium and thorium concentrations and activity ratios for all riverine phases (bedload, suspended load, dissolved load and colloids) from basaltic terrains in Iceland and the Azores. Small basaltic islands, such as these, are thought to account for ~ 25% of CO₂ consumed by global silicate weathering, and for ~ 45% of the flux of suspended material to the oceans. These data indicate that [U] and [Th] in the dissolved and colloidal fractions are strongly controlled by pH, and to a much lesser extent by levels of dissolved organic carbon (which are low in these environments). At high pH, basalt glass dissolution is enhanced, and secondary mineral formation (e.g. Fe-oxyhydroxides and allophane) is suppressed, resulting in high dissolved [U], and low colloidal [U] and [Th], indicating a direct chemical weathering control on elemental abundances. When the dissolved (²³⁴U/²³⁸U) activity ratio is >~1.3 (i.e. when physical weathering, groundwater contribution or soil formation are high), there is little isotope exchange between dissolved and colloidal fractions. At lower activity ratios, the dissolved load and colloids have indistinguishable activity ratios, suggesting that when chemical weathering rates are high, secondary clay formation is also high, and colloids rapidly adsorb dissolved U. Many of the suspended sediment samples have (²³⁴U/²³⁸U) activity ratios of > 1, which suggests that uptake of U onto the suspended load is important. Identical (²³⁰Th/²³²Th) in suspended, dissolved and colloidal samples suggests that Th, like U, is exchanged or sorbed rapidly between all riverine phases. This particle-reactivity, combined with poorly constrained contributions from groundwater and hydrothermal water, and short-term variations in input to soils (volcanic and glacial), suggests that U-series nuclides in riverine material from such basaltic terrains are unlikely to reflect steady state erosion processes.     

Natural and induced sinkholes of the Obruk Plateau and Karapınar-Hotamış Plain,Turkey

The number of sinkholes (locally known as obruks) has increased rapidly in recent years near Karap?nar, located in the semi-arid Konya Closed Basin in Central Anatolia. Nineteen sinkholes have formed in the last 33 years (1977–2009) as a result of the collapse of cavity roofs in the Neogene lacustrine limestone in the Obruk Plateau and beneath Quaternary lake sediments in the Karap?nar-Hotam?? Plain. Of these, 13 have formed within the past 4 years (2006–2009). The Obruk Plateau takes its name from the presence of several hundred paleo-sinkholes which formed as a result of natural processes during the Quaternary period. More recently, human activity has induced the formation of new sinkholes, which presents a hazard to life and property. Changing agricultural patterns have led to the opening of thousands of deep wells in recent years, and increased water pumping currently exceeds the sustainable yield of the aquifer. Thus the formation of sinkholes has been triggered by a combination of natural and human causes. The groundwater level has dropped almost 24 m in the vicinity of Karap?nar during the last 26 years (1983–2008). Approximately 8 m of this drop occurred within the 4 years prior to the study (2005–2008). Legally-binding precautions must be taken to prevent further water table decline, in order to decrease sinkhole formation within the basin in the years to come.     

Antibiotic resistant bacteria as bio-indicator of polluted effluent in the green turtles, Chelonia mydas in Oman

Antibiotic resistant bacteria were studied as bio-indicators of marine polluted effluents during egg-laying in green turtles. A non-invasive procedure for sampling oviductal fluid was used to test for exposure of turtles to pollution in Ras Al-Hadd, Oman, which is one of the most important nesting beaches in the world. Each sample was obtained by inserting a 15 cm sterile swab gently into the cloacal vent as the sphincter muscle is relaxed and the cloacal lining is unfolded to the outside. Forty turtles were sampled. A hundred and thirty-two species of bacteria from 7 genera were isolated. The dominant isolate was Citrobacter. Among the isolates 60.6% were multiple resistant to 15 tested antibiotics. The dominant resistance to antibiotics was ampicillin followed by streptomycin and sulphamethoxazole. Sampling oviductal fluid for resistant bacteria to antibiotics is valuable way to assess exposure to polluted effluents during feeding and migratory in turtles. Polluted effluents using bacteria as bio-indicator may influence reproductive potential in this endangered species.