Medium Depth Research Articles

Yield and photochemical activity of selected rice cultivars from Eastern India under medium depth stagnant flooding

Stagnant flooding (SF) is a serious threat for rice production in rainfed lowland areas of Southeast Asian countries. To overview the SF effect, photosynthetic performances and productivity were studied with three landraces (Ravana, Kamini, and Rashpanjor) and four high-yielding cultivars (Savitri, Savitri-Sub1, Gayatri, and Varshadhan) of rice under medium depth (40-50 cm) of water level. Stagnant flooding significantly increased the stem elongation and decreased yield and yield attributing parameters. The chlorophyll a fluorescence rises from O- to P-step with distinct J- and I-step were noticed in all the cultivars up to 75 d of SF. Prolonged flooding (> 2 months) perturbed both donor and acceptor side of PSII. Vitality indices (PIABS and PITOT) decreased greatly under prolonged SF. Analysis of O-J-I-P transients suggests that the information is useful for agricultural planning with the purpose to enhance rice yield under lowland medium depth SF.

Bearing capacity of embedded foundations using quasi-kinematic limit analysis

Bearing capacity of rectangular foundations, with varying aspect ratios (1 ≤ L/B ≤ 5) and embedded at shallow to medium depths (D/B ≤ 5), has been evaluated by using the three-dimensional cell-based smoothed finite elements quasi-kinematic limit analysis. The results have also been obtained for circular and strip foundations by performing exclusively the axisymmetric and plane strain analyses. The associated optimization problem has been solved by employing the semidefinite programming (SDP). Shape factors (sc, sq and sγ) and depth factors (dc, dq and dγ) are given as a function of soil internal friction angle (ϕ). The shape factors have been expressed as a function of L/B, on the other hand, the depth factors have been given as a function of D/B and L/B. A thorough comparison of the results has been made with the different solutions available in literature. The variations of (i) power dissipation function, (ii) maximum plastic shear strain rates, and (iii) the nodal velocities patterns, have also been examined to interpret the failure mechanism.

Distribution, abundance and fishing potential of mega-invertebrates in the sub-euphotic zone (150–535 m) in the Colombian Caribbean

There are no commercial fishing activities in the deep water of the Colombian Caribbean, but initial surveys have spotted species of great abundance that may have harvest potential. In this study, we report the findings of a systematic trawling of soft seafloor mega-invertebrate assemblages along the Colombian Caribbean coast (from the Gulf of Urabá to Punta Gallinas in La Guajira) in a depth range between 150 and 535 m (three strata: 150–300 m; 300–400 m; 400–535m). We analysed the spatial distribution, species composition, and size structure, as well as the relationship between species abundance and biomass (ABC curves) as an indicator of the state of the system. In the medium depth stratum of the northern zone, general species richness and abundance were highest, and the ABC curves suggest a pristine system state with no signs of community disturbance. The species Pleoticus robustus, Penaeopsis serrata, Aristaeomorpha foliacea, Metanephrops binghami and Plesionika longipes showed the highest abundance (> 60%), biomass (> 72%) and widest range of geographical and bathymetric distribution and may be candidates for a future fishery. However, prior to opening any fishery for these species, studies should be conducted on their life history parameters to estimate the catch fraction of the annual production that may be sustainably be harvested.

Classification and design of hydro-lenses

Subject of Research. The paper considers hydro-lenses for the study of the World Ocean, including its Arctic zone. The issues of work at shallow depths and the shelf are regarded as having been resolved; the work is actively carried out at medium depths, 300–500 meters, therefore, the projects involving the study of deep water become the most relevant. These tasks are complex and multidisciplinary and, surely, require large scientific, technical and financial investments for their solutions and are able to ensure the replacement of expensive imported equipment. In terms of complexity, they are not inferior to the issues of space exploration. Method. Maximum attention is paid to the design of specialized optical systems that provide the formation, input and transmission of visual information from distant objects, which cannot be obtained by any other means. It is important to understand the role and purpose of each element in the design of such systems. This knowledge helps the developer to find the optimal solution for selecting the starting point of the optical system. The design methods were based on the experience of ITMO University in the development of optical schemes for hydro-lenses and their implementation in national projects for the World Ocean exploration. The main approach used in the design of hydro-lenses involves combining the analysis of the known solutions, their classification, recommendations of opticians-experts skilled in the art, as well as structural and parametric synthesis with subsequent automated correction of lens circuits. In recent years, virtual prototyping of models of hydro-lenses and their interaction with the external environment has been actively used. Main Results. The main results and their practical significance consist in calculation procedure development for hydro-lenses intended for deep-sea exploration and the creation of a number of hydro-lenses for solving applied scientific problems. The paper presents diagrams of certain lenses. Practical Relevance. The developed hydro-lenses can be used to solve various scientific and economic problems at deep waters of the World Ocean, up to the maximum ones.

Effects of carbon concentration, pH, and bubbling depth on carbon dioxide absorption ratio in microalgae medium.

The microalgae-based CO2 sequestration is considered to be an effective technique with great potential to cope with carbon emission. However, most researches are only focused on microalgae; the effects of physicochemical factors, which are carbon concentration, medium pH, and bubbling depth, on absorption and utilization of supplied CO2 in culture is less known. In order to understand and improve CO2 absorption in microalgae culture, the effects of these three factors were studied with different levels and combinations. Results revealed that when medium carbon concentration increased from 4.76 to 95.24 mmol/L, CO2 absorption ratio increased by about 12%, 10%, 12%, and 11% at medium depths of 10, 20, 40, and 80 cm, with the initial pH 10.6 to 9.7 by bubbling CO2, respectively. As bubbling depth increased from 10 to 80 cm, CO2 absorption ratio increased by about 25%, 22%, and 25% at carbon concentrations of 4.76, 9.52, and 95.24 mmol/L, with the initial pH 10.6 to 9.7 by bubbling CO2, respectively. In range of 10.6-7.0, pH had no significant effect on CO2 absorption ratio (P > 0.05) when carbon concentration is below 9.52 mmol/L, while above 9.52 mmol/L, pH had significant effect on CO2 absorption ratio (P < 0.05). It was found for the first time that the effect of pH on the CO2 absorption ratio was affected by carbon concentration. In addition, equilibrium pH, at which the CO2 partial pressure in the medium equals to that in the air, of medium with different carbon concentrations was also determined. Overall, in microalgae culture for CO2 sequestration, increasing CO2 bubbling depth and keeping higher carbon concentration and higher pH can improve CO2 absorption ratio, which will optimize the biofixation of CO2 by microalgae furthermore.

Downhole pressure and chemical monitoring for CO2 and brine leak detection in aquifers above a CO2 storage reservoir

We assess the effectiveness of downhole monitoring of pressure and chemistry for detecting CO2 and brine leakage into underground sources of drinking water (USDW) overlying a geologic CO2 storage (GCS) reservoir. This assessment uses synthetic data sets generated in an uncertainty quantification (UQ) model framework. This framework combines the results of three model types: (1) a model of a hypothetical, 50-yr, 5-MT/yr GCS operation in the Vedder Fm. at the Kimberlina site in the southern San Joaquin Basin in California, USA, (2) models of CO2/brine leakage in legacy wells into overlying aquifers, and (3) models of CO2/brine plume migration in those aquifers. Leakage into overlying aquifers causes changes in pressure, CO2 saturation, and total dissolved solids (TDS), the latter being related to the solubility and speciation of CO2. This study captures the influence of leakage depth along the legacy well, regional groundwater flow, and aquifer heterogeneity on leak detection using downhole pressure and TDS monitoring.We consider CO2/brine leakage for legacy wells located at various distances from the CO2 injector at the Kimberlina site. Because gaseous CO2 is much less dense than supercritical CO2, the depth where leakage occurs along the wellbore is a key factor affecting the CO2, TDS, and pressure plumes. Supercritical CO2 that migrates upwards to depths less than 800 m undergoes a phase change to gaseous CO2, with the large volumetric expansion causing a large rise in pressure and a large spread in the TDS and pressure plumes. Because the pressure and TDS plumes migrate with the CO2 plume, they are strongly affected by regional groundwater flow and aquifer heterogeneity.We evaluated the likelihood of leak detection over a wide range of CO2/brine leakage-mass magnitude for downhole monitoring at various sensor depths, as well as for locations upgradient, downgradient, and laterally from the leaking well. Leak-detection effectiveness of downhole monitoring improves as the volumes of the CO2 and TDS plumes increase with cumulative CO2/brine leakage mass, groundwater gradient, and aquifer permeability. The effectiveness of pressure monitoring also increases strongly with CO2 leakage rate and can be useful for early detection of large leaks. Because TDS and pressure plumes migrate with the regional groundwater flow, downgradient monitoring wells are more effective than lateral or upgradient wells. Pressure monitoring is found to be more effective than TDS monitoring for shallow depths, while TDS monitoring is more effective at depths greater than about 600 m for this site. The addition of two monitoring depths to a single-depth monitoring well greatly improves leak detection. Monitoring three (shallow, medium, and deep) depths in the same well is found to be equally effective for pressure and TDS for the Kimberlina site. However, these comparisons are affected by the choice of detectable TDS and pressure thresholds, which depend on the level of unfilterable background noise for a specific site. For GCS sites like the Kimberlina site, with a thick sequence of overlying aquifers, unbroken by confining, low-permeability aquitard layers, an effective use of an individual monitoring well would be to monitor pressure at a shallow (<600 m) depth and to monitor TDS at a medium-depth (600−900 m) interval and for at least one deep (>900 m) interval. Because pressure and TDS changes evolve so gradually, continuous monitoring is not necessary.

Theoretical substantiation of the layout decisions of station complexes of the underground of medium depth (up to 40 m) in the engineering and geological conditions of Saint Petersburg

The development of a modern city and the increase in the occupied territory also involves the improvement of its transport infrastructure. In accordance with the sectoral scheme of development of the subway of St. Petersburg and the current backlog of its implementation requires a new approach to the implementation of the plan for the construction of the subway network. This article proposes the concept of space-planning, structural and construction solutions for metro stations of the ring line, as well as for the peripheral areas of the city. Over the past 10 years, there has been a rapid increase in population and active high-rise development of all areas of the city, increasing congestion of both urban and suburban roads, which leads to inefficiency of public and individual transport. For a long time there has been a problem of unloading the existing subway lines and exceeding the uncovered areas by available types of urban passenger transport, the main of which is the subway. To meet the needs of the population in comfortable transportation with minimal time required a large-scale approach to the implementation of the long-term plan for the development of the subway. Engineering-geological conditions of St. Petersburg are characterized by great complexity in the design and construction of underground structures. Water-saturated unstable sandy-clay soils, often of a belt structure, serve as the host medium for the objects of the underground of small and medium depth. The thickness of Quaternary deposits within the city has a large difference of absolute marks and is characterized by great heterogeneity. Relatively favorable conditions for the construction of underground structures are the layers of Cambrian clays, the full capacity of which varies from 12–20 m to 95–126 m relative to the earth’s surface. The root soils are characterized by sufficient density and uniformity with low water flows and moisture, which led to the deep laying of the vast number of station complexes and distillation tunnels of the St. Petersburg metro.

Myotomy of sternocleidomastoid muscle as a secondary procedure in laryngectomized patients.

The application of specific devices to seal the tracheal stoma in laryngectomized patients is critical for optimal pulmonary and phonatory rehabilitation. Indeed, an excessive stomal depth is one of the main causes of rehabilitation failure. In this context, division of the sternal heads of the sternocleidomastoid muscle (SCM) is a common technique, usually performed during the laryngectomy. We perform a myotomy of the sternal head of the SCM in deep and narrow tracheal stoma as a secondary procedure under local anesthesia, and here we describe the surgical steps of this procedure. The medium depth of the stoma is reduced, and no procedure-specific complications have been observed. Postoperative morphological features show a flattening of the peristomal area, and all patients have begun regular use of appropriate patches and filters. Secondary section of SCM is a safe, simple, and effective procedure in total laryngectomies with deep and narrow stoma.

Analysis of peak ground acceleration (PGA) using the probabilistic seismic hazard analysis (PSHA) method for Bengkulu earthquake of 1900 – 2017 period

This study was aimed to find out and analyze Peak Ground Acceleration (PGA) in order to mitigate the earthquake. The PGA map resulted was an acceleration map on bedrock with a probability exceeding 10% and 2% with the Probabilistic Seismic Hazard Analysis (PSHA) method for PGA in 50 years. The software used to analyze the Probabilistic Seismic Hazard Analysis (PSHA) method is USGS-PSHA. The data used was in the form of historical earthquake data from 1900 to 2017 and a depth of 1 km to 300 km. Earthquake magnitude ≥ 4.5 Mw with a research limit of 2.53° - 7.58° SL and 96.1° - 106.1° EL from the International Seismological Center (ISC) earthquake catalog, ISC-EHB Bulletin, United States Geological Survey (USGS) and The Geophysical Climatology Meteorology Institution (BMKG), a radius of 500 km from the border of Bengkulu Province. The results show that the most earthquakes for shallow depths with a magnitude of 4.5 Mw - 5.9 Mw as much as 2805 times, while for medium depths at magnitude 4.5 Mw - 5.9 Mw as much as 642 times. The probabilistic calculations exceeding 10% are 0.24 gal - 0.86 gal and probabilistic calculation exceeding 2% is 0.36 gal - 1.35 gal. The areas exposed to the danger zone are Lebong, Rejang Lebong, Kepahiang, Mukomuko, North Bengkulu and Bengkulu City. Whereas the regions included in the medium zone are Seluma and Bengkulu Tengah. And the areas of the safe zone are Kaur and South Bengkulu.

Agronomic Performances of Rice Lines on Non-Tidal Swampland

A successful rice production on swampland would require a planting material from high yielding varieties adaptated to the swampy ecosystem. This study was carried out to compare the growth and yield characteristics of five rice lines and a check variety as grown on non-tidal swampland. The lines were F4 generation of bulk selection from the crosses involving Bengkulu swamp rice landraces (Hanafi Putih, Tigo-tigo, Harum Curup, and Lubuk Durian) and high yielding varieties for the irrigated field (Sidenuk and Bestari). The trial was conducted on a shallow non-tidal swampland with stagnant inundation no more than 50 cm in depth often occurred during the plant life cycle. The lines and the check variety (Inpara 4) were arranged in a randomized complete block design with three replications. Observations were made for the agronomic performances of the plant, including plant height, total tiller number clump-1, effective tiller number clump-1, heading date, maturity date, panicle length, grain number panicle-1, 100-grain weight, and grain yield clump-1. Significant variation among the genotypes was found for all observed traits. On average, the evaluated lines showed comparable growth and yield performances to the check variety. Tigo-tigo × Bestari was the tallest line and potential for medium depth swampland. This line showed good overall agronomic performances and yielded relatively higher than the check variety, but delayed in attaining maturity. For shallow swampland, Hanafi Putih x Sidenuk exhibited the most potent line by having good overall agronomic and yield performances, except late in maturity. For early maturing line, Lubuk Durian x Hanafi Putih showed its potential for shallow swampland. Although this line was not the best, it showed better overall agronomic performances than the check variety. Keywords: F4 lines, growth and yield performance, rice landrace, swampland, plant maturity

A critical assessment of the reliability of predicting subsidence phenomena induced by hydrocarbon production

Predictive analysis of the spatial and temporal evolution of the subsidence induced by hydrocarbon exploitation could be affected by a high uncertainty also related to the a priori identification of the most realistic deformation parameter values. In fact, deformation behaviour of the involved formations is not constant but evolves according to the increasing strain caused by fluid pressure drop. Especially shallow medium depth clastic formations (which contain most of the reserves in the largest known reservoirs) could exhibit an important non-linear influence of strain on formation stiffness.The scope of this research is to provide insight into how reliable the prediction of the subsidence could be as a function of adopted pseudo-elastic values related to the non-linear poro-elastic behaviour of clastic formations. To this end, a series of multi-variable sensitivity analyses were developed to quantify the discrepancy in subsidence forecast deriving from the assumption of constant (static or dynamic) pseudo-elastic parameters values along all reservoir production life instead of inputting into the model a decay curve, which describes the progressive degradation of the pseudo-elastic parameters. The case study, even if synthetic, is a compound of standard features representative of gas-production from a clastic reservoir so as to analyse the response of a macro category.The results of all the analysed scenarios (which differ in terms of reservoir depth, Gas Originally in Place and shape factor) allow the identification of the reference confidential intervals of static and dynamic assumptions vs the decay curve hypothesis. Furthermore, they show that even if the mechanical response of the reservoirs evolves towards the static modulus during production, the relative induced subsidence is approximated with higher accuracy by the constant dynamic modulus assumption. The results of the sensitivity analysis on synthetic models were validated via the analysis of a real gas reservoir.

Swirling in the ocean: Immature loggerhead turtles seasonally target old anticyclonic eddies at the fringe of the North Atlantic gyre

In a highly heterogeneous open ocean, swirling oceanographic structures such as eddies drive ocean productivity and aggregate many predators, including oceanic sea turtles. During early life, juvenile loggerhead turtles can spend more than a decade feeding on gelatinous zooplankton in the open ocean, but the way they use mesoscale eddies is still poorly understood. Here, we investigated the relationships between (1) the distribution and (2) the diving behaviour of immature loggerhead turtles of the North-East Atlantic and mesoscale eddies. For this purpose, 28 turtles were satellite tracked from the Azores archipelago. Using the Residence Time (RT) analysis as a proxy to identify high-use areas, the tracks and dive data of the turtles as well as drifter trajectories were analysed in relation to eddy characteristics, which include eddy radius, amplitude, type (cyclonic vs. anticyclonic), lifetime and region (inner core, outer core, periphery). The turtles dispersed widely using many distinct high-use areas. Although there were always more cyclones than anticyclones over the study region, the individuals seasonally associated more with the inner cores of old anticyclonic eddies, likely due to the higher productivity of decaying anticyclones. The comparison between passive drifters and turtles’ movements showed an active swimming behaviour from the turtles rather than a passive advection through currents. Three dive types were identified, and the one associated with the highest RT was characterized by dives of medium duration and depths in the inner cores of eddies. This study is the first to highlight strong affinities of oceanic loggerhead turtles for old anticyclonic eddies around the Azores, suggesting a greater complexity of these warm-core eddies that appear to be much more productive than cyclones.

Deepened winter snow significantly influences the availability and forms of nitrogen taken up by plants in High Arctic tundra

Climate change may alter nutrient cycling in Arctic soils and plants. Deeper snow during winter, as well as summer warming, could increase soil temperatures and thereby the availability of otherwise limiting nutrients such as nitrogen (N). We used fences to manipulate snow depths in Svalbard for 9 consecutive years, resulting in three snow regimes: 1) Ambient with a maximum snow depth of 35 cm, 2) Medium with a maximum of 100 cm and 3) Deep with a maximum of 150 cm. We increased temperatures during one growing season using Open Top Chambers (OTCs), and sampled soil and vascular plant leaves throughout summer 2015. Labile soil N, especially inorganic N, during the growing season was significantly greater in Deep than Ambient suggesting N supply in excess of plant and microbial demand. However, we found no effect of Medium snow depth or short-term summer temperature increase on soil N, presumably due to minor impacts on soil temperature and moisture. The temporal patterns of labile soil N were similar in all snow regimes with high concentrations of organic N immediately after snowmelt, thereafter dropping towards peak growing season. Concentrations of all N forms increased at the end of summer. Vascular plants had high N at the start of growing season, decreasing as summer progressed, and leaf N concentrations were highest in Deep, corresponding to the higher soil N availability. Short-term summer warming was associated with lower leaf N concentrations, presumably due to growth dilution. Deeper snow enhanced labile soil organic and inorganic N pools and plant N uptake. Leaf 15N natural abundance levels (δ15N) in Deep indicated a higher degree of utilization of inorganic than organic N, which was especially pronounced in mycorrhizal plants.

A novel packet exchanging strategy for preventing HoL-blocking in fat-trees

Fat-tree interconnection network is one of the most popular and widely-used networks in massively parallel processing systems. Its superb characteristics such as deterministic routing, in-order delivery and providing the same performance as adaptive routing methods have made it an attractive interconnection network. However, due to its deterministic routing as well as simultaneously usage of switch links, Head of Line (HoL)-blocking may occur in buffers during high traffic workload. In order to mitigate this problem, in this paper, a novel strategy in switch buffers based on the blocking of the paths is proposed. It has been shown that combining packets with different blocked paths can reduce congestion by packet exchanging. To exchange packets, we used short and medium depth buffers and also considered two exchanging states; consecutive and non-consecutive. This novel strategy provides a trade-off between the performance improvement and reduction of buffers’ depths, while doesn’t change the delivery order of the packets. Simulation results show that in comparison with one buffer in each switch, 22% and 33% average network latency is improved with consecutive and one unit non-consecutive exchanging states respectively and also the depth of buffers in each switch is reduced 43.75% and 37.5% in comparison with multiple buffers.

IMPACT OF HYPERBARIC STRESS ON LIPID COMPOSITION OF BLOOD PLASMA AND PHYSIOLOGICAL-BIOCHEMICAL CHARACTERISTICS OF ERYTHROCYTES IN DIVERS: PREVENTION OF VIOLATIONS BY VEGETABLE POLYPHENOLS

There was studied lipid composition of blood plasma and erythrocyte membranes, physiological characteristics of erythrocytes in divers, exposed to extreme factors of the hyperbaric environment in the process of the occupational activity. There was observed a group of 10 male divers from 25 to 30 years of age, whose work is associated with the systematic implementation of submarine dives at medium and large depths (20-60 m) using compressed air for breathing. The influence of hyperbaric stress was shown to be accompanied by the change in a ratio of fatty acids in the total lipids of blood plasma and erythrocyte membranes. In total lipids of blood plasma and erythrocyte membranes the number of all kinds of saturated fatty acids (myristic acid, palmitic acid, stearic acid), the monounsaturated fatty acids (palmitoleic acid) was increased and an amount of polyunsaturated fatty acids of n-6 family (arachidonic acid) and n-3 (eicosapentaenoic acid) was reduced, which caused a change in physicochemical properties of erythrocytes, permeability, and lability. The increase in the amount of cholesterol in the erythrocyte membranes correlates with its elevation in blood plasma. There was an increase in the volume of erythrocytes by 5% and diameter by 13%, due to the inclusion of cholesterol in the membrane. It was recorded a shift in the threshold of hemolysis start at 0.50 ± 0.02% NaCl and its completion at 0.40 ± 0.01% NaCI. Preventive administration of the Kalifen food supplement for two months before the dive would help to remove metabolic disorders caused by the hyperbaric factors.

Depth of the mining exploitation and its progress in the time, and a random dispersion of observed terrain subsidence and their derivatives

Paper presents the own research results conducted on shaping of random dispersion of the observed deformation indicators of mining terrain, especially subsidence and their derivatives such as inclinations and curvatures. Research were carried out on two examples of the underground mining exploitation, which was done at the small and medium depths. In both cases exploitation took place in an intact rock mass and in the one seam. Hard coal was extracted by the use of the longwall system with a roof rocks cave-in. Exploitation influences were observed after termination of the next exploitation stages and on the two measuring lines, which were stabilized perpendicularly to the longwalls runs. There were calculated the values of the variability coefficients of a random dispersion of the measured deformation indicators depending on an exploitation development in the time and a depth of the performed works. Generally, it can be said that a random dispersion of deformation process of terrain surface grows together with an exploitation depth and an increase its scope, what is especially visible in case of curvatures.

Thermodynamics of Deep Supercritical Geothermal Systems

The study of water is very important in science and for many industrial applications, such as steam turbines, high pressure devices and supercritical cycles. In aquifers, hydrocarbon reservoirs, geothermal systems and atmosphere-ocean interactions, water is one of the most important fluids in action. Specifically, geothermal reservoirs contain water in a wide thermodynamic range. The temperature gradient between the core and the surface of the Earth results from a continuous flow of natural heat, embracing all kind of thermal energy resources that can be classified in terms of their profoundness, going from shallow depths (102 m), to medium depths (103 m), and to even deeper depths (104 m), reaching the immense temperatures of molten rocks. Warm aquifers below oil reservoirs, hot dry rock, submarine reservoirs, and engineered geothermal reservoirs are examples of profound geothermal systems. The fluids in very deep reservoirs can be at supercritical thermodynamic conditions, at more than 400°C and pressures larger than 220 bar, having higher fluid density, more volumetric enthalpy and heat available. They could provide twenty times as much power, per unit fluid volume, as the normal geothermal fluids used today. During the span of human life, deep geothermal energy represents practically an infinite potential. The aim of this paper is to provide a computational description of water thermodynamics at supercritical conditions showing the power it represents. The water properties are defined in terms of the Helmholtz potential or free energy, and are calculated for single phase, liquid, vapor and supercritical, as functions of density or pressure, and temperature. These properties are internal energy, enthalpy, entropy, specific isochoric heat, specific isobaric heat, compressibility, bulk modulus, Joule coefficient, speed of sound, thermal expansivity and thermal diffusivity.

Finite-element model to simulate ground-improvement technique of rapid impact compaction

Rapid impact compaction (RIC) has been used effectively as a ground improvement at medium depth technique for granular soils. RIC is normally used to increase bearing capacity, reduce potential settlements and mitigate liquefaction. This paper presents a calibrated three-dimensional cap-plasticity finite-element model (FEM) to simulate ground improvement using RIC. The results of 107 RIC field compaction points were used to calibrate and validate the FEM. Numerical outcomes of the FEM showed good agreement with the field compaction results. The FEM was further used to propose a relationship between the soil bearing capacity and the number of hammer blows for engineering practice. This is attained by performing pushover analysis of a spread footing resting on RIC improved soils with different numbers of RIC blows. The RIC, circular 1·5 m anvil was used as the spread footing. The applied stresses that produced 25 mm settlement are considered the improved soil bearing capacity. Also, the paper presents a recommendation for the optimum number of blows after which more blows will have no significance.

Plant Colonization of Green Roofs Is Affected by Composition of Established Native Plant Communities

Human activities associated with urbanization have negatively affected the biodiversity of native plant communities globally. Establishing native species assemblages on green roofs may help conserve native plant diversity in urban areas, but these assemblages are susceptible to colonization by species from the surrounding landscape. In natural communities, colonization from the regional species pool reflects the filtering effects of both abiotic and biotic factors, but the relative effects of these factors on green roof colonization are not well understood. To address this knowledge gap, we studied colonization dynamics of 10 green roofs in New York City (NY, USA), each with 12 split-plots planted with an erect C4 graminoid dominant (Hempstead Plains: HP) and a tuft C3 graminoid and forb dominant (Rocky Summit: RS) species assemblage derived from native communities. Six of the 12 plots contained shallow growing medium, while the other six contained deeper growing medium. Resident plants were planted in May 2010. Fifty-eight non-resident plant species colonized plots between August 2011 and August 2012, with two native and 10 non-native species accounting for 90% of total colonist dry mass. Colonist dry mass and richness decreased with increasing resident plant cover, but the effects of growing medium depth on colonist dry mass and richness differed between assemblages. Forbs accounted for 81% of the colonist dry mass from the HP assemblage, but just 31% in the RS assemblage. Further, forbs accounted for over 95% of colonist dry mass in June and July, while graminoids accounted for over 95% of colonist dry mass in August. These results indicate colonization of planted green roofs may be strongly affected by the composition of established plant assemblages and that these effects may vary temporally, even within a single growing season. Further, the inconsistent effects of growing medium depth suggest that niche overlap and complementarity in rhizosphere dynamics may influence colonization more in some systems compared with others. Additional research is required to describe the effects of colonist management strategies, as well as the roles of priority effects, niche complementarity and community assembly, on long-term dynamics of colonization on green roofs planted with native plants.

Groundwater level changes with a focus on agricultural areas in the Mid-Atlantic region of the United States, 2002–2016

Climate change impacts all water sources, including high quality groundwater that supplies agricultural irrigation in many regions of the United States. This study assessed groundwater level changes in the U.S. Mid-Atlantic region with a focus on cultivated areas. Trends of groundwater level were estimated using linear regression, and examined for shallow, medium, and deep depths across physiographic regions of Mid-Atlantic. A hotspot analysis was conducted to identify spatial clusters of wells with rising or declining groundwater levels. In addition, differences in the percentage of cultivated area with declining groundwater between cultivated land categories was examined at the county level. From 2002–2016, the Mid-Atlantic region had an overall decline in groundwater level (0.06 m/yr, 95% CI: 0.03, 0.09) although groundwater changes varied by physiographic regions. The Coastal Plain physiographic region was dominated by declining groundwater wells (48%) and had the most significant groundwater level declines (0.23 m/yr, 95% CI: 0.19, 0.26). Significant groundwater level rises were detected in Southern Virginia adjacent to the Chesapeake Bay (0.92 m/yr on average), which could be due to the cessation of groundwater withdrawal from one of the region's largest groundwater users. In the Mid-Atlantic region, shallow groundwater was found to have slight rising trends (0.08 m, p < 0.05) while deeper groundwater showed distinctive declining trends (1.36 m, p < 0.05) between 2002 and 2016. There were significantly more cultivated areas with declining groundwater levels (88% vs. 35%, p < 0.05) in counties with high percentages of cropland (> 50%) compared to areas covered by less cropland. As climate and human pressures increase, it will be critical to identify and evaluate alternative water sources, such as reclaimed water, to sustain agricultural production and protect groundwater resources.