Amplitude Of Shrinkage Research Articles

The Swelling–Shrinkage Properties of Intact and Disturbed Clayey and Marly Soils: The Density Effect

Expansive soils commonly encountered beneath foundations often lead to structural issues inducing expensive repairs. With the increase of the frequency of dry summers and irregular rainfall patterns, the clayey and marly soils become more and more sensitive to shrinking and swelling phenomena. So to find solutions and improve the knowledge on such phenomena especially in temperate countries where the saturation state is considered as the usual soil state, the impact of the soil density on shrinkage was studied by varying the compaction mode and introducing a swelling step before shrinkage. As expected, dynamically or statically compacted clayey or marly soils exhibited high shrinkage deformation when the soil had a low density. The swelling before shrinkage impacted the soil structure but ultimately had a low effect on shrinkage deformation. Swelling deformation was also influenced by density; the denser the soil, the more sensitive the compacted soil became to swelling. Furthermore, compaction modes induced differences in swelling or shrinkage amplitude that couldn’t be explained by microstructural observations. Finally, results demonstrated that intact soil behavior after shrinkage could be extrapolated from swelling–shrinkage tests conducted on remolded soil samples, thus decreasing the cost of field investigations.

Spatio-Temporal Dynamics of Diffusion-Associated Deformations of Biological Tissues and Polyacrylamide Gels Observed with Optical Coherence Elastography.

In this work, we use the method of optical coherence elastography (OCE) to enable quantitative, spatially resolved visualization of diffusion-associated deformations in the areas of maximum concentration gradients during diffusion of hyperosmotic substances in cartilaginous tissue and polyacrylamide gels. At high concentration gradients, alternating sign, near-surface deformations in porous moisture-saturated materials are observed in the first minutes of diffusion. For cartilage, the kinetics of osmotic deformations visualized by OCE, as well as the optical transmittance variations caused by the diffusion, were comparatively analyzed for several substances that are often used as optical clearing agents, i.e., glycerol, polypropylene, PEG-400 and iohexol, for which the effective diffusion coefficients were found to be 7.4 ± 1.8, 5.0 ± 0.8, 4.4 ± 0.8 and 4.6 ± 0.9 × 10-6 cm2/s, respectively. For the osmotically induced shrinkage amplitude, the influence of the organic alcohol concentration appears to be more significant than the influence of its molecular weight. The rate and amplitude of osmotically induced shrinkage and dilatation in polyacrylamide gels is found to clearly depend on the degree of their crosslinking. The obtained results show that observation of osmotic strains with the developed OCE technique can be applied for structural characterization of a wide range of porous materials, including biopolymers. In addition, it may be promising for revealing alterations in the diffusivity/permeability of biological tissues that are potentially associated with various diseases.

The pulse of the tree is under genetic control: eucalyptus as a case study.

The pulse of the tree (diurnal cycle of stem radius fluctuations) has been widely studied as a way of analyzing tree responses to the environment, including the phenotypic plasticity of tree-water relationships in particular. However, the genetic basis of this daily phenotype and its interplay with the environment remain largely unexplored. We characterized the genetic and environmental determinants of this response, by monitoring daily stem radius fluctuation (dSRF) on 210 trees from a Eucalyptus urophylla×E. grandis full-sib family over 2years. The dSRF signal was broken down into hydraulic capacitance, assessed as the daily amplitude of shrinkage (DA), and net growth, estimated as the change in maximum radius between two consecutive days (ΔR). The environmental determinants of these two traits were clearly different: DA was positively correlated with atmospheric variables relating to water demand, while ΔR was associated with soil water content. The heritability for these two traits ranged from low to moderate over time, revealing a time-dependent or environment-dependent complex genetic determinism. We identified 686 and 384 daily quantitative trait loci (QTL) representing 32 and 31 QTL regions for DA and ΔR, respectively. The identification of gene networks underlying the 27 major genomics regions for both traits generated additional hypotheses concerning the biological mechanisms involved in response to water demand and supply. This study highlights that environmentally induced changes in daily stem radius fluctuation are genetically controlled in trees and suggests that these daily responses integrated over time shape the genetic architecture of mature traits.

A Concept for Accurate Edge-Coupled Multi-Fiber Photonic Interconnects

The alignment and fixation of multiple single-mode optical fibers to photonic integrated circuits is currently a challenging, expensive, and time-consuming task. In this paper, we present a concept for a sub-micrometer accurate multi-fiber array, where fibers are actively aligned with respect to each other and fixated to a flat carrier using ultraviolet-curable adhesive. Adhesives are prone to shrinkage, which can disturb the fiber alignment. As a result, especially, the fixation process forms the bottleneck in reaching the required alignment and not the alignment process itself. Simulations are performed to investigate the sensitivity of process variables on the adhesive bond geometry, which is important for the shrinkage amplitude. Furthermore, an experimental setup has been designed and fabricated to measure the shrinkage-induced fiber displacement for three selected types of adhesives. The results show a controllable adhesive shrinkage, where fibers can be aligned with a position reproducibility of $\pm {\text{40}}$ nm, which is more than sufficient for the most critical fiber alignment applications. With this concept, an important step can be made in enabling sub-micrometer accurate photonic interconnects in a cost-effective way, which is suitable for automated production.

Chemical shrinkage of cement pastes and mortars at very early age: Effect of limestone filler and granular inclusions

This article presents a study on the influence of limestone filler and granular inclusions on the chemical shrinkage of cementitious matrices at very early age (⩽24 h). Measurements of chemical shrinkage and hydration degree are carried out on cement pastes and mortars. During this study, two cement types (CEM 1 and CEM 2), two water-to-cement ratios (W/C = 0.30 and 0.40) and three substitution rates of cement by limestone filler (LF/C = 0; 0.25 and 0.67) are used. The effects of aggregate shape (glass beads and natural sand), aggregate-to-cement mass ratio (A/C = 0.5 and 1) and particle size distribution (D = 1 and 2 mm) on the chemical shrinkage and the hydration rate are quantified. The results obtained show that limestone filler causes an acceleration of both Le Chatelier’s contraction and hydration process since the very first hours of hydration. In addition, the chemical shrinkage amplitude is not significantly influenced by the presence of aggregates. Finally, the presence of limestone filler and granular inclusions does not cause significant modification of the quasi-linear relation observed at early age between the chemical shrinkage and the hydration degree of the cementitious matrices.

Apoptosis in serum-deprived vascular smooth muscle cells: evidence for cell volume-independent mechanism.

Shrinkage is the earliest hallmark of cells undergoing apoptosis. This study examines the role of this phenomenon in the onset of vascular smooth muscle cell (VSMC) apoptosis triggered by growth factor withdrawal. In hyperosmotic media, VSMC showed the same amplitude of shrinkage but were more resistant to apoptosis than endothelial, epithelial and immune system cells. As with growth factor withdrawal, apoptosis in hyperosmotically-shrunken VSMC was sharply potentiated by transfection with E1A-adenoviral protein and was suppressed by activation of cAMP signaling as well as by the pan-caspase inhibitor z-VAD.fmk. Both cell shrinkage and apoptosis in VSMC-E1A treated with hyperosmotic medium were potentiated under sustained Na+, K+ pump inhibition with ouabain that was in contrast to inhibition of apoptosis documented in ouabain-treated, serum-deprived cells. After 1-hr incubation in serum-deprived medium, VSMC-E1A volume declined by approximately 15%. Transfer from hypotonic to control medium decreased VSMC-E1A volume by approximately 25% without any induction of apoptosis. Neither swelling in hyposmotic medium nor dissipation of the transmembrane gradient of K+ and major organic osmolytes protected serum-deprived VSMC-E1A from apoptosis. Thus, our results show that similarly to immune system, endothelial and epithelial cells, extensive VSMC shrinkage in hyperosmotic medium leads to the development of apoptosis. In contrast to hyperosmotic medium, the modest cell volume decrease occurring in serum-deprived VSMC does not contribute to triggering of the apoptotic machinery.

A new approach to determine autogenous shrinkage of mortar at an early age considering temperature history

Shrinkage, settlement, and thermal deformations of concrete start to develop as soon as the casting is finished. The majority of standard tests currently used to measure free deformations are carried out on hardened concrete. Therefore, the prediction of thermal and other stresses at an early age cannot be determined. This article describes the design and the operation of an experimental device used for measuring the volume change of mortar in relation to the real temperature history. Measurements are carried out on a mortar having a water/cement (W/C) ratio of 0.35 and started approximately 20 min after the addition of water in the mixture up to 24 h of hydration. The measured deformation includes autogenous shrinkage and thermal expansion or contraction caused by the temperature changes induced by the heat of cement hydration. An experimental method is proposed to uncouple these deformations. The investigations show that the autogenous shrinkage amplitude is strongly affected by the temperature history of mortar. Therefore, for a good estimate of the shrinkage amplitudes of cement-based material, temperature must be taken into account in testing.

Interpreting changes in stem diameter in rose plants

Sixteen adult rose plants (Rosa hybrida cv. Sweet Promise) were grown in rockwool in a phytotron. Water uptake was estimated by computing the difference between the rate of nutrient solution supply and the rate of leaching, continuously measured using a high‐precision flowmeter. Transpiration was measured using a balance continuously recording the loss of weight in the entire system. Changes in stem diameter were recorded using linear variable differential transducers placed at the base of four developing shoots and on their corresponding basal stems. Changes in stem diameter were related to changes in the water content of 16 plants. The amplitude of shrinkage in daytime stem diameter and daily increase in stem diameter was lower in basal stems. Radial hydraulic resistance to water diffusion in stems seems to be very low and stem reservoirs appear to be very early sensors of water depletion. When the nutrient solution supply was suppressed, the amplitude of the daily increase in stem diameter and transpiration rates were reduced one and one‐and‐a‐half days later, respectively. When water depletion became more severe, stem diameter decreased from one day to another. The amplitude of daily stem shrinkage increased sharply for 6 days after watering was stopped, while the bulk modulus of elasticity of leaves decreased, probably as a result of damage to the cell wall.

Effect of cold bending and welding on buckling of ring-stiffened cylinders

The BOSOR5 computer program for elastic plastic buckling of shells of revolution is used for calculation of bifurcation buckling of cold bent and welded ring-stiffened cylinders under external pressure. Residual stresses and deformations from cold bending and welding are included in the model for buckling under service loads by introduction of these manufacturing processes as functions of a time-like parameter which ensures that the material in the analytical model experiences the proper sequence of loading prior to and during application of the service loads. The cold bending process is first simulated by a thermal loading cycle in which the temperature varies linearly through the shell wall thickness, initially increasing in time to simulate cold bending around a die and then decreasing in time to simulate springback to a final somewhat larger design radius. The welding process is subsequently simulated by the assumption that the material in the immediate neighborhoods of the welds is cooled below the ambient temperature by an amount that leads to weld shrinkage amplitudes typical of those observed in tests. Buckling loads are calculated for a configuration including and neglecting the cold bending and welding processes. These predictions are compared to values obtained from tests on two nominally identical specimens, one carefully machined and the other fabricated by cold bending the shell and then welding machined ring stiffeners to it.