Globally, coal mining wastes (CMWs) are associated with significant environmental and economic costs. Processing CMW into an ingredient of foam concrete is a promising solution but the behaviour of ...this particular construction material has not been sufficiently evaluated, especially during the initial period of cement hydration. The purpose of this paper is to present novel laboratory set-up and experimental procedures designed to investigate the early age behaviour of hydrating foam concrete samples made with a CMW from Poland. Two types of tests were devised to simulate air-curing conditions and water-curing conditions, respectively. These tests were carried out in custom-built unsaturated oedometer cells, and the matric suction in the test samples was monitored for approximately 14 days, using Warwick high capacity tensiometers. Experimental results show that in both curing conditions, a higher matric suction during cement hydration corresponds to a denser sample at the end of the monitoring period. A comparison of water-cured and air-cured samples also reveals different responses to CMW inclusion in their mix designs. The responses can be convincingly explained based on complementary test data and idealised capillary tube models adapted for the hydrating foam concrete samples.
•A novel laboratory set-up, incorporating high capacity tensiometers (HCTs) into purpose-built unsaturated oedometer cells, is proposed to investigate the curing behaviour of foam concrete during early age hydration. The incorporation of the HCTs made it possible to directly monitor the matric suction evolution of the mix and the corresponding interplays depending on the foam concrete samples’ (water- or air-) curing conditions.•The influence of natural sand replacement by coal mining waste (CMW) in the foam concrete mix has been studies, together with the corresponding effects on the evolutions of matric suction and porosity during the early age hydration.•Two different types of tests were devised for measuring the impacts of different curing environments on foam concrete properties. The first type was adapted for a water-curing condition and is akin to a chemical shrinkage test. The second type was adapted for an air-curing condition where water inflow was not permitted into the hydrating foam concrete sample over the monitoring period. In both cases. The evolution and interplays of matric suction were studied in correspondence with formation/stabilisation of the pore networks.•Simplified capillary models are proposed that meaningfully describe the rather complex kinetics of foam concrete hydration associated to the matric suction variations.
A fundamental way to schedule irrigation is through the monitoring and management of soil water tension (SWT). Soil water tension is the force necessary for plant roots to extract water from the ...soil. With the invention of tensiometers, SWT measurements have been used to schedule irrigation. There are different types of field instruments used to measure SWT, either directly or indirectly. Precise irrigation scheduling by SWT criteria is a powerful method to optimize plant performance. Specific SWT criteria for irrigation scheduling have been developed to optimize the production and quality of vegetable crops, field crops, trees, shrubs, and nursery crops. This review discusses known SWT criteria for irrigation scheduling that vary from 2 to 800 kPa depending on the crop species, plant product to be optimized, environmental conditions, and irrigation system. By using the ideal SWT and adjusting irrigation duration and amount, it is possible to simultaneously achieve high productivity and meet environmental stewardship goals for water use and reduced leaching.
In many educational institutes and industries, the contact angle and surface tension analysis are done to measure the quality of a solid surface and of a liquid. In order to determine these, the ...sessile and pendant droplet method are the most widely used metrics, which are conventionally obtained using commercial goniometer/tensiometer. In view of the growing concern regardingcompact and inexpensive but accurate experimental devices, we have developed a low-priced in-house goniometer/tensiometer. This device has the benefit of easiness, compactness, and movability over the conventional measurement instruments. In this study, we have used the commercial Drop image advanced as well as the Drop analysis plugin in ImageJ with high quality sharp edges images to compute static contact angle and surface tension values. Detailed procedure to measure them have been discussed in this work. To validate the apparatus, various water-based solutions have been considered. The surface tension values obtained using the apparatus are in good agreement with those reported in the literature. However, the apparatus needs to validate for highly wettable and volatile fluids. The efficacious manifestation of this device to determine the contact angle is a compelling improvement in the area as it disrupts the trendof a bench designated setup which is heavy, bulky and expensive and are not suitable for field work. The standard threaded syringe-based low-priced goniometer/tensiometer fabricated is affordable, being less than 40 USD or 3000 INR. Variety of water-based solutions like Millipore water, SDS solution at CMC * (8.1 mM), SDS solution at CMC/2, SDS solution at 2xCMC have been considered for validation and compared with surface tension values. Such a low-cost goniometer prototype can serve the technological needs of scientific research labs, in imparting practical learning about repeatability and highly beneficial for industrial applications.
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•The particle size and concentration have significant roles on the impact on the normal behavior of lung surfactant.•The particle asymmetry affects the extent of interaction with lung ...surfactant and creates a more disordered structure.•Nanoparticles form clusters and clusters show higher disruptive effect on the behavior of lung surfactant.
One of the initial barriers encountered by the airborne nanoparticles (NPs) upon entry into the body is the lung surfactant (LS), which plays a vital role in maintaining the normal respiratory cycle of the lungs. Interaction between gold nanoparticles (AuNPs), which are commonly used in many areas, especially in pharmaceutical applications due to their functional features and LS has been evaluated by combining Langmuir Trough (2D) and Pendant-Drop tensiometer (3D) approaches. AuNPs were synthesized via Turkevich method and AuNP clusters were prepared by using dithiothreitol (DTT) with the different concentrations. Model LS was extracted from a bovine lung and brought into vesicular form after purification. Our results showed that AuNP-DTT clusters are able to penetrate into the LS monolayer and vesicles, change the normal behavior of air-buffer interface, organization of the molecules and phase behavior of the system. In 2D studies, it is seen that the interaction of AuNPs and AuNP-DTT clusters decreases the surface pressure of phase transition region which indicates decreasing the elasticity with a similar manner for first 3 h. In the longer periods, the monolayer presented an increased resistance to compression, indicating the low compressibility of monolayer. After 7 h interaction with AuNP-DTT clusters, at the same surface area (48 cm2), the π of LS films can just reach ∼30 mN·m−1 instead of ∼45 mN·m−1 which proves the induction of the isotherm to form a more disordered structure with lower cohesion between the molecules. In 3D studies, it is found that there becomes a competitive adsorption between LS vesicles and AuNP-DTT clusters in the long-term interaction which may enhance the pulmonary toxicity of the inhaled nanostructure. The ultimate insight provided by this study is to evaluate the toxicity of the interaction of asymmetrical NPs on biological barriers with a realistic approach. As a result of our investigations, it is proved that long-term exposure of anisotropic clusters can cause potential adverse effects on the healthy environment and breathing cycle of lungs more than smaller individual counterparts with the same concentration.
The purpose of this study was to investigate age-related differences in Achilles tendon loading during gait. Fourteen young (7F/7M, 26 ± 5 years) and older (7F/7M, 67 ± 5 years) adults without ...current neurological or orthopaedic impairment participated. Shear wave tensiometry was used to measure tendon stress by tracking Achilles tendon wave speed. The wave speed-stress relationship was calibrated using simultaneously collected tensiometer and force plate measures during a standing sway task. Tendon stress was computed from the force plate measures using subject-specific ultrasound measures of tendon moment arm and cross-sectional area. All subjects exhibited a highly linear relationship between wave speed squared and tendon stress (mean R2 > 0.9), with no significant age-group differences in tensiometer calibration parameters. Tendon wave speed was monitored during treadmill walking at four speeds (0.75, 1.00, 1.25, and 1.50 m/s) and used to compute the stress experienced by the tendon. Relative to young adults, older adults exhibited 22% lower peak tendon wave speeds. Peak tendon stress during push-off in older adults (24.8 MPa) was 32% less than that in the young adults (36.7 MPa) (p = 0.01). There was a moderate increase (+11%) in peak tendon stress across both groups when increasing speed from 0.75 to 1.50 m/s (main effect of speed, p = 0.01). Peak tendon loading during late swing did not differ between age groups (mean 3.8 MPa in young and 4.2 MPa in older adults). These age-related alterations in tendon tissue loading may affect the mechanobiological stimuli underlying tissue remodeling and thereby alter the propensity for tendon injury and disease.
•Shear wave sensors can measure superficial tendon stress noninvasively.•Achilles tendon stress is 32% lower in older than younger adults during walking.•Achilles tendon loading is lower in older adults across a range of walking speeds.•Diminished loads could alter mechanobiological stimuli underlying tendon remodeling.
•Tensiometer-based irrigation management improved strawberry yield significantly.•Tensiometer-based irrigation improved water use efficiency on most sites.•For strawberry, irrigation between −10 and ...−15kPa suits most conditions.
Effective and adapted criteria for irrigation scheduling are required to improve yield and water use efficiency (WUE) and reduce the environmental impacts associated with water and nutrients losses by runoff and leaching. In this study, field-scale experiments were conducted at four commercial strawberry production sites with contrasting soil and climatic conditions. Within each site, the influence of different soil matric potential-based irrigation thresholds (IT) on yield and WUE was evaluated. Matric potential-based irrigation management was also compared with common irrigation practices used by producers in each site's respective areas. At Site 1 (silty clay loam; humid continental (Dfb) climate), an IT of −15kPa improved yields by 6.2% without any additional use of water relative to common irrigation practices. At Site 2, with similar soil and climatic conditions, the irrigation treatments did not affect yield and the matric potential-based management decreased WUE relative to common practices. However, the results suggested that maintaining the soil matric potential lower than −9kPa could induce stressing conditions for the plants. At Site 3 (sandy loam; Mediterranean (Cs) climate), the best yield and WUE were obtained with an IT of −8kPa and suggested that WUE could be further improved by implementing high-frequency irrigation. At Site 4 (clay loam; Mediterranean (Cs) climate), results suggested that an IT between −10 and −15kPa could optimize yield and WUE, and matric potential-based irrigation considerably reduced leaching under the root zone relative to common practices. Considering the results from all sites, an IT of −10kPa appears to be adequate as a starting point for further optimizing irrigation under most field conditions.
•Automating irrigation activation with tensiometer is feasible for greenhouse zucchini.•The threshold of soil matric potential modifies yield of fruit and efficiencies.•The best soil matric potential ...is −25kPa considering agronomic-environmental aspects.•Soil salinity increase after growing season, independently of soil matric potential.
Greenhouse horticultural crops are characterized by high levels of efficiency and productivity of irrigation water. But they still can and must be improved, especially in arid areas. The objective of this research was to study the effect of the soil matric potential level on the bio-productivity of zucchini crop, the water use efficiency (WUE) and nutrients use efficiency by changing the threshold of soil matric potential. An experiment was conducted in greenhouse-grown zucchini on a sand-mulched soil and fertigation with inorganic fertilizer. Automatic activation of irrigation through an electronic tensiometer and three treatments were applied: Activation of irrigation to −10kPa and application of volume of 1.5Lm−2 (T1), activation of irrigation to −25kPa and application of volume of 2.0Lm−2 (T2) and activation of irrigation to −40kPa and application of volume of 3.0Lm−2 (T3). Yield, leaf area, biomass, water consumption, WUE and nutrients, drainage volume and physical-chemical parameters of the soil were determined. The results show that T2 slightly reduced the weight of the fruit with respect to T1, but not the number of fruit, obtaining a significantly lower consumption of water. Lower weight fruits and less number of fruits were obtained by T3. Reducing the soil moisture tension level increased substantially water consumption as a result of the differences in vegetative growth (leaf area and biomass) in plants. Highest values of WUE and nutrients use efficiency were registered by T2 and T3. In none of the treatments, drainage was obtained. Soil physical-chemical parameters were not affected by treatments. Independently of soil matric potential, increased soil salinity occurred after the growing season. The soil matric potential of −25kPa was the best considering agronomic and environmental aspects, as the most efficient use of water and nutrients obtaining a commercial production of 15kgm−2.
Previous study showed the triceps surae exhibits spring-like behavior about the ankle during walking in children with cerebral palsy. Thus, the work generated by the triceps surae is diminished ...relative to typically developing children. This study investigated whether the quadriceps offset the lack of triceps surae work production in children with cerebral palsy who walk in crouch.
Seven children with cerebral palsy (8-16 yrs) and 14 typically developing controls (8-17 yrs) walked overground at their preferred speed in a motion analysis laboratory. Shear wave tensiometers were used to track patellar and Achilles tendon loading throughout the gait cycle. Tendon force measures were coupled with muscle-tendon kinematic estimates to characterize the net work generated by the quadriceps and triceps surae about the knee and ankle, respectively.
Children with cerebral palsy generated significantly less triceps surae work when compared to controls (P < 0.001). The reverse was true at the knee. Children with cerebral palsy generated positive net work from the quadriceps about the knee, which exceeded the net quadriceps work generated by controls (P = 0.028).
There was a marked difference in functional behavior of the triceps surae and quadriceps in children with cerebral palsy who walk in crouch. In particular, the triceps surae of children with cerebral palsy exhibited spring-like behavior about the ankle while the quadriceps exhibited more motor-like behavior about the knee. This redistribution in work could partly be associated with the elevated energetic cost of walking in children with cerebral palsy and is relevant to consider when planning treatments to correct crouch gait.
•Characterized Achilles and patellar tendon loading with shear wave tensiometry.•Triceps surae exhibits spring-like behavior in crouch gait due to cerebral palsy.•Quadriceps exhibit motor-like, positive work in crouch due to cerebral palsy.•Redistribution in work relevant for treatment planning to correct crouch.
Here we present a method for measurement of the rate of solvent absorption by perfluorosulfonic acid (PFSA) membranes using a force tensiometer. The method presented here can be used as a tool to ...understand solvent absorption and should provide a rationale for designing catalyst inks for direct coating processes since it is necessary to understand how the absorption rate – on a time scale of seconds to minutes – compares to the time scales of the coating process in order to minimize membrane swelling. This method allows for rapid screening of the absorption and swelling behavior of different solvents and mixtures. Using this method, the absorption of water/1-propanol mixtures were measured for three thicknesses of Nafion PFSA membrane – Nafion 1135, Nafion 115, and Nafion 117. We find that the absorption rate is dependent on the ratio of the solvents as well as the thickness of the membrane. The analysis indicates that the highest absorption rate occurs when the mass percentage of 1-propanol in the mixture is 50%, whereas the lowest rates are for pure water and 1-propanol. In addition, membrane distortion also occurs most quickly for the 50% 1-propanol mixture. Our results suggest that catalyst inks that are highly rich (≥90%) in water or 1-propanol are likely best for direct coating as such formulations will minimize absorption and swelling.
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•Solvent absorption studied formulate catalyst inks for direct coating on membrane.•Force tensiometer method developed to measure solvent uptake in Nafion membranes.•Pure water and 1-propanol absorbed slower than water/1-propanol mixtures.•Mixtures of ≥90% water likely best to minimize swelling during coating.
Pendant capsule elastometry Hegemann, Jonas; Knoche, Sebastian; Egger, Simon ...
Journal of colloid and interface science,
03/2018, Letnik:
513
Journal Article
Recenzirano
Odprti dostop
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We provide a C/C++ software for the shape analysis of deflated elastic capsules in a pendant capsule geometry, which is based on an elastic description of the capsule material as a ...quasi two-dimensional elastic membrane using shell theory. Pendant capsule elastometry provides a new in situ and non-contact method for interfacial rheology of elastic capsules that goes beyond determination of the Gibbs- or dilational modulus from area-dependent measurements of the surface tension using pendant drop tensiometry, which can only give a rough estimate of the elastic capsule properties as they are based on a purely liquid interface model. Given an elastic model of the capsule membrane, pendant capsule elastometry determines optimal elastic moduli by fitting numerically generated axisymmetric shapes optimally to an experimental image. For each digitized image of a deflated capsule elastic moduli can be determined, if another image of its undeformed reference shape is provided. Within this paper, we focus on nonlinear Hookean elasticity because of its low computational cost and its wide applicability, but also discuss and implement alternative constitutive laws. For Hookean elasticity, Young’s surface modulus (or, alternatively, area compression modulus) and Poisson’s ratio are determined; for Mooney-Rivlin elasticity, the Rivlin modulus and a dimensionless shape parameter are determined; for neo-Hookean elasticity, only the Rivlin modulus is determined, using a fixed dimensionless shape parameter. Comparing results for different models we find that nonlinear Hookean elasticity is adequate for most capsules. If series of images are available, these moduli can be evaluated as a function of the capsule volume to analyze hysteresis or aging effects depending on the deformation history or to detect viscoelastic effects for different volume change rates. An additional wrinkling wavelength measurement allows the user to determine the bending modulus, from which the layer thickness can be derived. We verify the method by analyzing several materials, compare the results to available rheological measurements, and review several applications. We make the software available under the GPL license at github.com/jhegemann/opencapsule.
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