Large Mat Research Articles

A comprehensive study on an integrated approach for water hyacinth management to conserve natural water resources in India

The rapid growth of the free-floating invasive weed Water Hyacinth (WH) has caused an environmental and social menace in most water bodies. Its large mat formation not only affects the underlying aquatic species by blocking sunlight and depleting oxygen, but it also interferes with commercial activities such as fishing and transportation. Public health is also affected as it provides shelter for disease-causing mosquitoes. Additionally, it is a bio-indicator of water bodies polluted with heavy metals. Removing and managing this weed is crucial for conserving natural water resources. Various manual, mechanical, chemical, and biological methods have been tried and tested to eradicate this plant. However, each method has its limitations, and the reoccurrence of this weed in a short time calls for an innovative approach to finding sustainable solutions. Recent studies focus on utilizing this weed for commercial purposes rather than eradicating it. The high cellulose and hemicellulose content in the plant make it an excellent source for renewable fuel production. It also finds application in industries that prepare animal food, compost, and bio-fertilizers due to the high nutrient content. Many states in India are utilizing the WH plant to produce eco-friendly and creative products, thus helping in local employment generation. This study's research contribution is evaluating the advantages and drawbacks of weed removal methods, the potential of WH plants in phytoremediation and biofuel production, case studies of successful alternate uses of WH plants, and possible action plans for economically and ecologically sustainable plant management to conserve water resources in India. The specific outcome of the study is that water hyacinth management is not the responsibility of a single body or entity, but rather the responsibility of different stakeholders and their combined efforts to combat this issue at a national level.

Design of large geotextile mat cofferdam over deep soft clay

This article describes an extensive investigation of the failure mechanisms of a large geotextile mat cofferdam over a deep soft clay layer, where the large geotextile mat was filled with sand. Finite element (FE) analysis was conducted to provide insight into the behaviour of large geotextile mats. The FE results were validated against 1 g model test data and centrifuge test data prior to undertaking a detailed parametric study. It is found that large geotextile mat cofferdam over deep soft clay has two distinctive types of failure mechanisms – global and local failure mechanisms. The global failure mechanism showed the whole dam sank downwards together, and the local failure mechanism included a central standing ridge with two dam sides sliding downwards. A formula, based on the results of the parametric study, was proposed to distinguish the potential failure mechanism of the dam and the foundation soil. For these two different failure mechanisms, both limiting fill height and safety factor of the dam could be predicted using the equations obtained from this study. Finally, a design framework was proposed to provide guidance for designing the large geotextile mat cofferdam over deep soft clay under construction.

Modification of large microbial mat deformation structures before burial: A modern case study

The presence of microorganisms gives remarkable plasticity and flexibility to wet sediments. Under these circumstances, a coherent microbial mat is developed, which is loosely attached to the underlying sediment layer. These thick microbial mats are capable of being lifted from the underlying sediments in response to high-energy events, such as currents and waves forming several types of synsedimentary microbial mat deformation structures. This study analyses excellent examples of these structures developed in Paso Seco (Argentina), a modern coastal flat colonized by microbial mats frequently inundated during storms, and the modifications that affect them before burial. To achieve this, the hydrodynamic conditions in the coastal flat over time were interpreted from water level records obtained with HOBO loggers. Field photographs were obtained to document the microbial structures (such as flipped-overs, tear mats, roll-ups, mat chips, and folds) covering the area after a high-energy event and over the course of the following two years. Specifically, emphasise was put in roll-up structures because of their large size. Sediment samples were extracted to make thin sections for petrography analysis. Once the microbial structures are formed, they show gradual changes caused by the hydrodynamic conditions that control the sedimentary environment, and on several occasions, these changes are preserved in the sedimentary profile. Our observations and measurement of modern sedimentary structures and the in-situ documentation of their evolution may be helpful for the identification and interpretation of analogous sedimentary structures in the fossil record, which could have undergone similar modifications prior to their burial.

Centrifuge tests and numerical simulations on vertical bearing capacity of mat foundation on marine clay seabed

Mat foundation is a new type of jack-up wind power installation platform suitable for clay seabed, which avoids the problems of excessive insertion and extraction difficulties of spudcan foundation on soft clay seabed. Evaluating the vertical bearing capacity of the mat foundation on the clay seabed is of great significance for the safe operation of jack-up platform in marine environment. In this research, the vertical bearing characteristics of mat foundation on horizontal and sloping clay seabed were studied through centrifuge tests. Then, numerical simulations were conducted to study the vertical bearing capacity of the full-scale mat foundation on clay seabed, in which the effects of the large mat foundation size, pile leg insertion depth, preloading, consolidation degree of soil, and soil plasticity were analyzed. The results show that the vertical bearing capacity of the mat foundations on the sloping seabed is reduced, and the soil under the mat foundation shows obvious sliding failure. The contribution of the insertion depth of pile legs on the horizontal bearing capacity is more obvious than that of the vertical bearing capacity. The enhancement of the vertical bearing capacity is mainly due to the dissipation of the excess pore pressure and the increase of the mean effective stress of the soil. The effects of preloading, consolidation degree, and soil property on the vertical bearing capacity of the mat foundation are significant.

Behavior of the geotextile reinforced dykes on sand-overlying-clay deposit

An extensive investigation on the performance of large geotextile mat dykes on stiff-over-soft soil deposits is carried out undertaken through numerical simulation in this paper. The large mat is reinforced by geotextiles with a new type of arrangement, i.e. non-uniform geotextile reinforcement. The numerical model is validated against centrifuge test data and other previously testing results, prior to conduct parametric study. It is found that large geotextile reinforced dykes on sand overlying clay fails through a global mechanism that the whole dam sank downwards together. It is found that the thickness of the sand layer, the width of the dyke base, and the shear strength of soft clay are the key influence factors on the stability of the dyke. A design flow chart is then proposed to quantity the performance of the geotextile mat dyke with non-uniform reinforcement, in terms of predicting allowable dyke fill height and the corresponding safety factor, which can be employed to provide refer for its design and construction.

The History of Things in Ralf Andtbacka'sWunderkammer

The History of Things in Ralf Andtbacka's<i>Wunderkammer</i>

Effects of inorganic nutrient enrichment on the carrageenan yield, growth, and ice-ice disease occurrence of red alga Kappaphycus striatus

One of the problems in Kappaphycus farming is the slow growth in some farms due to nutrient insufficiency caused by overstocking. In the southern Philippines, most seaweed farmers practice inorganic nutrient enrichment of Kappaphycus to boost growth and decrease ice-ice disease occurrence using ammonium phosphate at an average concentration of 8.82 g L-1. In this study, experiments with Kappaphycus striatus enriched with inorganic nutrients were carried out at Pasiagan, Bongao, Tawi-Tawi, southern Philippines, using different inorganic nutrients (T1=8.82 g L-1 of urea, T2=8.82 g L-1 of phosphorus, and T3=control) within 45 days. Seaweeds were enriched in these three inorganic solutions for 30 seconds, placed into a large mat, covered with canvas, and left overnight. After 15 days, findings showed that the specific growth rates of T1 (6.99% day-1) and T3 (6.72% day-1) groups were significantly higher than the T2 (5.84% day-1) group (p&lt;0.05). Inorganic nutrient enrichment did not significantly influence the occurrence of ice-ice disease. Moreover, inorganic nutrient enrichment did not affect the carrageenan yield after 45 days. K. striatus nutrient-enriched with urea could increase growth at day 15, but no effect on the occurrence of ice-ice disease and carrageenan yield. Hence, inorganic nutrient enrichment using urea provides a positive effect to farmed K. striatus by enhancing its growth without affecting its health and carrageenan yield.

Taisui TS-2007S, a Large Microbial Mat Discovered in Soil in China.

In this study, Taisui TS-2007S, a previously unidentified biological object discovered in soil in China, was identified. TS-2007S was shown to contain abundant carbohydrates but a scarcity of protein, fat, and minerals. The exopolymers of TS-2007S showed FT-IR spectra that were similar to those of xanthan gum (XG) but that were dissimilar to those of polyvinyl alcohol (PVA). The NMR spectra of TS-2007S exopolymers in D2O were similar to those of PVA but differed from those of xanthan gum. Unlike PVA, TS-2007S exopolymers and xanthan gum were not soluble in dimethyl sulfoxide (DMSO). Furthermore, the exopolymers contained many monosaccharide components, including fucose, rhamnose, mannose, and glucuronic acid in a molar ratio of 87.90:7.49:4.45:0.15. The exopolymers also included traces of glucuronic acid, galactose, and xylose. Taken together, these results suggest that the exopolymers are microbial extracellular polymeric substances (EPSs). The microbial community structure in TS-2007S showed that the predominant bacterial, archaeal, and fungal phyla were Proteobacteria, Euryarchaeota, and Ascomycota at high relative abundances of 90.77, 97.15, and 87.43%, respectively, different from those observed in water and soil environments. Based on these results, we strongly propose that TS-2007S should be defined as a microbial mat formed in soil.

Behavior of offshore dike using non-uniform geotextile mats on clay-overlaying-sand soil deposits

This paper performs finite element (FE) analysis to investigate the behaviour of a large geotextile mat offshore dike on clay-overlaying-sand soil deposits, which is reinforced by a new type of non-uniform thick geotextiles technique. A FE model is generated and validated against laboratory centrifuge testing data. A comprehensive parametric study is then conducted to examine the influences of soil properties for sand and clay, dam base width, tensile capacity of geotextile, and slope gradient of the dike. Two types of failure mechanisms, i.e. local failure and global failure are observed for large geotextile mat dikes on clay-overlaying-sand soil deposits, which are affected by the squeezing effect of the underlaying sand layer. Empirical formulae are derived based on the numerical results. A design method is then proposed for predicting the maximum tolerable fill height of the large geotextile mat dike on clay-overlaying-sand soil deposit, and to access the stability of the dike.

Effect of rockfill berm on the stability of large geotextile mat dikes on soft clay

This paper investigates the effect of rockfill berms on the stability of large geotextile mat dikes filled with sand built upon soft clay. Finite element analyses were conducted aiming to provide insight into the design of large geotextile mat dikes by using rockfill berms reinforcement. The FE results were validated against previously published data, with good agreement obtained. A parametrical study was then carried out to explore the failure mechanism, limiting stack height and geotextile tension distribution of the dikes. Based on the FE results, two failure mechanisms, i.e. the so-called global and local failure mechanisms, were observed. A formula was proposed to predict the critical width of the base of the dike to differentiate the two mechanisms. It is found that rockfill berm can increase the limiting stack height and safety factor of the dike, and the shape of rockfill berms has a significant influence on the stability of large geotextile mat dikes. Finally, a general design method was proposed to evaluate the required dike height and factor of safety for the design of the large basal-reinforced geotextile mat dikes, which can provide a guidance for practical application.

A Physically-Active Approach to Early Number Learning

This study evaluates the efficacy of a physically-active number learning game for young preschoolers. The intervention adapts Ramani and Siegler’s (Child Develop 79(2):375–394, 2008) successful The Great Race by modifying the mode of play from seated at a table to jumping with two feet on a large game mat. 75 children (mean age: 46 months) in the first year of a 2-year Title I preschool program were assessed in the fall on enumeration, verbal counting, cardinal principle knowledge (CPK), numeral recognition, and magnitude comparisons; children with a strong conceptual understanding of the cardinality principle were screened out (n = 11) of the intervention. 64 children were randomly assigned to the jumping game, the original seated game, or to a no-intervention control group. For the intervention, children met with an experimenter for four, 15–20-min sessions over a 3-week period and post-intervention assessments were completed 1 week later. All children completed a year-end assessment 5 months after the post-intervention assessment. Of the 64 children in the intervention group, 51 had complete data from all three time points. Repeated measures ANOVA and chi-square tests assessed the effectiveness of the intervention on children’s number knowledge and skills; models tested for the main effects of time and group and the interaction of time*group. Although all numeracy measures showed significant improvement over time, no differences between groups over time emerged. The absence of intervention effects is discussed in the context of intentionally aligning children’s number skills and knowledge with teacher practices and recent early numeracy interventions that target counting and set labelling.

Behavior of Large Geotextile Mat Cofferdam with a New Arrangement of Geotextile Reinforcement Stiffness Lying on Soft Sediments

Abstract This paper proposes a new arrangement of geotextile reinforcement stiffness for large geotextile mat cofferdams that often suffer from the failure of the bottom layer mat. Cofferdams using...

Shaping Perception: Designing for Participatory Facilitation of Collaborative Geometry

Geometris is a technologically enabled, body-scale, educational game, in which collaborating players recreate target polygons, prompted on a digital screen, by activating a set of sensors–vertices on a large physical mat interface. We report on an evaluation study that draws on theoretical frameworks from ecological dynamics, genetic epistemology, and socio-cultural semiotics. Micro-analysis of three adult–child groups at play implicates two design features supporting mediated development of geometry skills: (1) spatial distribution across two displays – the screen and the mat – poses cross-display figural mapping as a tactical problem whose perceptual solution constitutes the game’s learning objective; (2) a multi-sensor input interface – the mat’s ‘vertices’ – enables flexible divisions of group labor for scaffolding solution enactment. We put forth the construct of participatory facilitation – an emergent interaction pattern in groups with inter-personal differences in content-domain knowledge and sensorimotor co-ordination. We tentatively generalize principles for designing informal educational activity architecture that create opportunities for relative experts to enculturate content learning via participatory facilitation.

The carbonic anhydrase activity of sinking and suspended particles in the North Pacific Ocean

AbstractThe enzyme carbonic anhydrase (CA) is crucial to many physiological processes involving CO2, from photosynthesis and respiration, to calcification and CaCO3 dissolution. We present new measurements of CA activity along a North Pacific transect, on samples from in situ pumps, sediment traps, discreet plankton samples from the ship's underway seawater line, plankton tows, and surface sediment samples from multicores. CA activity is highest in the surface ocean and decreases with depth, both in suspended and sinking particles. Subpolar gyre surface particles exhibit 10× higher CA activity per liter of seawater compared to subtropical gyre surface particles. Activity persists to 4700 m in the subpolar gyre, but only to 1000 m in the subtropics. All sinking CA activity normalized to particulate organic carbon (POC) follows a single relationship (CA/POC = 1.9 ± 0.2 × 10−7 mol mol−1). This relationship is consistent with CA/POC values in subpolar plankton tow material, suspended particles, and core top sediments. We hypothesize that most subpolar CA activity is associated with rapidly sinking diatom blooms, consistent with a large mat of diatomaceous material identified on the seafloor. Compared to the basin‐wide sinking CA/POC relationship, a lower subtropical CA/POC suggests that the inventory of subtropical biomass is different in composition from exported material. Pteropods also demonstrate substantial CA activity. Scaled to the volume within pteropod shells, first‐order CO2 hydration rate constants are elevated ≥ 1000× above background. This kinetic enhancement is large enough to catalyze carbonate dissolution within microenvironments, providing observational evidence for CA‐catalyzed, respiration‐driven CaCO3 dissolution in the shallow North Pacific.

Torsional Response Induced by Lateral Displacement and Inertial Force

Eccentric distribution of stiffness, damping, and mass of a structure, and spatially non-uniform ground motion input to a long or large base mat of a structure are well-known causes of torsional response. We have discovered that the torque generated by horizontal displacement and perpendicular inertial force, which we call the Q- effect, can be a cause of torsional response. We formulated the equation of motion of a single finite-size mass-linear elastic shear and torsion spring model and clarified the resonance condition of the torsional response to sinusoidal ground acceleration. Time-history response analysis verified that the torsional response forms beat and the maximum torsional response of the simulation result agrees with that theoretically predicted. Further time-history response analysis conducted of white noise ground acceleration showed that even one-directional white noise ground acceleration can induce torsional response in a linear elastic system without any structural eccentricity.

Microbial Communities and Their Predicted Metabolic Functions in Growth Laminae of a Unique Large Conical Mat from Lake Untersee, East Antarctica

In this study, we report the distribution of microbial taxa and their predicted metabolic functions observed in the top (U1), middle (U2), and inner (U3) decadal growth laminae of a unique large conical microbial mat from perennially ice-covered Lake Untersee of East Antarctica, using NextGen sequencing of the 16S rRNA gene and bioinformatics tools. The results showed that the U1 lamina was dominated by cyanobacteria, specifically Phormidium sp., Leptolyngbya sp., and Pseudanabaena sp. The U2 and U3 laminae had high abundances of Actinobacteria, Verrucomicrobia, Proteobacteria, and Bacteroidetes. Closely related taxa within each abundant bacterial taxon found in each lamina were further differentiated at the highest taxonomic resolution using the oligotyping method. PICRUSt analysis, which determines predicted KEGG functional categories from the gene contents and abundances among microbial communities, revealed a high number of sequences belonging to carbon fixation, energy metabolism, cyanophycin, chlorophyll, and photosynthesis proteins in the U1 lamina. The functional predictions of the microbial communities in U2 and U3 represented signal transduction, membrane transport, zinc transport and amino acid-, carbohydrate-, and arsenic- metabolisms. The Nearest Sequenced Taxon Index (NSTI) values processed through PICRUSt were 0.10, 0.13, and 0.11 for U1, U2, and U3 laminae, respectively. These values indicated a close correspondence with the reference microbial genome database, implying high confidence in the predicted metabolic functions of the microbial communities in each lamina. The distribution of microbial taxa observed in each lamina and their predicted metabolic functions provides additional insight into the complex microbial ecosystem at Lake Untersee, and lays the foundation for studies that will enhance our understanding of the mechanisms responsible for the formation of these unique mat structures and their evolutionary significance.

Batch Fabrication of Customizable Silicone‐Textile Composite Capacitive Strain Sensors for Human Motion Tracking

This paper presents design and batch manufacturing of a highly stretchable textile‐silicone capacitive sensor to be used in human articulation detection, soft robotics, and exoskeletons. The proposed sensor is made of conductive knit fabric as electrode and silicone elastomer as dielectric. The batch manufacturing technology enables production of large sensor mat and arbitrary shaping of sensors, which is precisely achieved via laser cutting of the sensor mat. Individual capacitive sensors exhibit high linearity, low hysteresis, and a gauge factor of 1.23. Compliant, low‐profile, and robust electrical connections are established by fusing filaments of micro coaxial cable to conductive fabric electrodes of the sensor with thermoplastic film. The capacitive sensors are integrated on a reconstructed glove for monitoring finger motions.

Palladium nanoparticles supported on amine-functionalized glass fiber mat for fixed-bed reactors on the effective removal of hexavalent chromium by catalytic reduction

Palladium nanoparticles were deposited on the amine-grafted glass fiber mat (GFM-NH2) catalyst support by a conventional impregnation process followed by the borohydride reduction in aqueous solution at room temperature to create the designed Pd/GFM-NH2 catalyst. By the use of large size glass fiber mat without nano/mesopores as the catalyst support, the internal mass transfer limitations due to the existence of nano/mesopores on the catalyst support were eliminated and the Pd/GFM-NH2 catalyst could be easily separated from treated water due to the large size of the catalyst support. Batch experiments demonstrate its good catalytic reduction performance of Cr(VI) with formic acid as the reducing agent. It also demonstrated an efficient Cr(VI) removal and stability in a lab-prepared, packed fixed-bed tube reactor for the continuous treatment of Cr(VI)-containing water. Thus, it has a good potential for the catalytic reduction of Cr(VI) in the water treatment practice.

A simplified approach to predict neutral plane and estimate drag forces on drilled shafts resulting from deformation in soil caused by a heavily loaded adjacent shallow foundation using ‘Isodefers’

Construction of foundations close to each other, which results in substantial interaction between them, has become a common practice. However, not much literature is available for practicing engineers to analyse and design deep and shallow foundations when they are constructed adjacent to each other. This study analyses one such scenario where a structure supported on drilled shafts was supposed to be constructed adjacent to another structure supported on a large mat foundation with heavy floor load. A detailed parametric study using finite element techniques was performed to better understand stress distributions and develop simplified methods to analyse this type of problems. Lateral stress and drag forces on the shafts resulting from the heavy load on the mat foundation were identified to be the key factors. This paper is focused on estimating the drag forces. A deformation bulb under a uniformly loaded square foundation, similar to the well-known pressure bulb, is proposed. A new term ‘Isodefers’ has been proposed to refer the lines of equal deformation. Isodefers are a significant tool for practicing engineers to understand vertical deformation distribution below a uniformly loaded square area and estimate drag forces on nearby deep foundations by determining its neutral plane.

Seismic Analyses of Soil Pressure against Embedded Mat Foundation and Pile Displacements for a Building in Moderate Seismic Area

Seismic analyses of a pile under a large rigid basement foundation embedded in the homogeneous soil layer were performed practically by a response displacement method assuming a sinusoidal wave form. However, it is hard to take into account the characteristics of a large mat foundation and a heterogeneous soil layer with the response displacement method. The response displacement method is relevant to the 2D problems for longitudinal structures such as tunnel, underground cave structure, etc., but might not be relevant with isolated foundations for building structures. In this study, seismic pile analysis by a pseudo 3D finite element method was carried out to compare numerical results with results of the response displacement method considering 3D characteristics of a foundation-soil system which is important for the building foundation analyses. Study results show that seismic analyses results of a response displacement method are similar to those of a pseudo 3D numerical method for stiff and dense soil layers, but they are too conservative for a soft soil layer inducing large soil pressures on the foundation wall and large pile displacements due to ignored foundation rigidity and resistance.