scholarly journals Influence of Environmental Factors on the Swelling Capacities of Superabsorbent Polymers Used in Concrete

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2185
Author(s):  
Andre Jung ◽  
Manuel B. Endres ◽  
Oliver Weichold
Keyword(s):  
Water Uptake ◽  
Uv Irradiation ◽  
Standard Procedure ◽  
Strong Dependence ◽  
Bound Water ◽  
Water Vapor Sorption ◽  
Rilem Technical Committee ◽  
Superabsorbent Polymers ◽  
Actual Weight ◽  
Major Interest

Superabsorbent polymers (SAP) are of major interest as materials to control the cement hydration process. The swelling behavior of the SAPs significantly influences the performance of the resulting concrete by slowly releasing polymer-bound water in order to maintain a consistent w/c value. A round-robin test conducted by the RILEM Technical Committee 260-RSC showed that the same batch of polymer can lead to large deviations in concrete performance and this was assumed to originate in different storage conditions of the SAP. In this contribution the change in the performance of two SAPs, a crosslinked poly(acrylate) and a crosslinked poly(acrylate-co-acrylamide), was assessed after ageing in standard climate, at 50 °C, and under UV irradiation. During storage in standard climate or 50 °C, ageing led to dehydration of the SAP, and this subsequently led to a higher water uptake during swelling. By contrast, UV irradiation reduced the water uptake, most likely as a result of photo-crosslinking. Dynamic water vapor sorption experiments indicated a strong dependence of the water uptake on both the ambient humidity and the temperature. As a result, cement mixtures containing SAP must be calculated on the dry mass of the SAP rather than the actual weight on site. A standard procedure of how to pack and handle SAP to be used in concrete is also provided.

scholarly journals A thermodynamic formulation of root water uptake

2016 ◽  
Vol 20 (8) ◽  
pp. 3441-3454 ◽  
Author(s):  
Anke Hildebrandt ◽  
Axel Kleidon ◽  
Marcel Bechmann
Keyword(s):  
Soil Water ◽  
Water Uptake ◽  
Water Distribution ◽  
Bound Water ◽  
Root Water Uptake ◽  
Flow Path ◽  
Thermodynamic Evaluation ◽  
Entire Flow ◽  
Soil Water Distribution

Abstract. By extracting bound water from the soil and lifting it to the canopy, root systems of vegetation perform work. Here we describe how root water uptake can be evaluated thermodynamically and demonstrate that this evaluation provides additional insights into the factors that impede root water uptake. We derive an expression that relates the energy export at the base of the root system to a sum of terms that reflect all fluxes and storage changes along the flow path in thermodynamic terms. We illustrate this thermodynamic formulation using an idealized setup of scenarios with a simple model. In these scenarios, we demonstrate why heterogeneity in soil water distribution and rooting properties affect the impediment of water flow even though the mean soil water content and rooting properties are the same across the scenarios. The effects of heterogeneity can clearly be identified in the thermodynamics of the system in terms of differences in dissipative losses and hydraulic energy, resulting in an earlier start of water limitation in the drying cycle. We conclude that this thermodynamic evaluation of root water uptake conveniently provides insights into the impediments of different processes along the entire flow path, which goes beyond resistances and also accounts for the role of heterogeneity in soil water distribution.

Two-Phase Hygrothermal Diffusion in an Epoxy Adhesive

2006 ◽  
Vol 258-260 ◽  
pp. 453-460
Author(s):  
Sylvain Popineau ◽  
C. Rondeau-Mouro ◽  
Christine Sulpice-Gaillet ◽  
Martin E.R. Shanahan
Keyword(s):  
Water Uptake ◽  
Bound Water ◽  
Epoxy Adhesive ◽  
Mathematical Treatment ◽  
Water Decomposition ◽  
Two Phase ◽  
Gravimetric Data ◽  
Diffusion In Polymers ◽  
Two Phases ◽  
Mass Increase

Water diffusion in polymers can often be approximated by a Fickian description, but a 2- phase model was proposed some years ago by Carter and Kibler (C&K), often referred to as “Langmuirtype” diffusion, by analogy with the Langmuir theory of adsorption. The two phases in question correspond to “mobile” and “bound” diffusant molecules. In this study, we have considered water uptake in an epoxy resin (an adhesive), employing gravimetry. A good, overall, empirical agreement with the C&K mathematical description of total mass increase with time has been obtained. In many applications of the C&K theory when used to quantify diffusion of water in polymers, only total water uptake is considered as a datum. However, a simple mathematical treatment of the theory enables the separate mobile and bound contributions to be isolated. These supplementary data have been used to try to get a better understanding of the meaning of the terms “mobile” and “bound” phases. Deuterium NMR analysis has been employed to study the mobility of the absorbed water. Decomposition of spectra has permitted us to assign two signals to the fractions of “mobile” and “bound” water. Analysis of peak evolution and a comparison with gravimetric data lead us to suggest that the “mobile” phase corresponds to diffusing molecules, whereas the “bound” phase corresponds to “clusters”.

scholarly journals A thermodynamic formulation of root water uptake

2015 ◽  
Vol 12 (12) ◽  
pp. 13383-13413
Author(s):  
A. Hildebrandt ◽  
A. Kleidon ◽  
M. Bechmann
Keyword(s):  
Root System ◽  
Water Uptake ◽  
Water Distribution ◽  
Bound Water ◽  
Root Water Uptake ◽  
Flow Path ◽  
Thermodynamic Evaluation ◽  
Flux Boundary Condition ◽  
Physically Based ◽  
Energy Domain

Abstract. By extracting bound water from the soil and lifting it to the canopy, root systems of vegetation perform work. Here we describe how the energetics involved in root water uptake can be quantified. The illustration is done using a simple, four-box model of the soil-root system to represent heterogeneity and a parameterization in which root water uptake is driven by the xylem potential of the plant with a fixed flux boundary condition. We use this approach to evaluate the effects of soil moisture heterogeneity and root system properties on the dissipative losses and export of energy involved in root water uptake. For this, we derive an expression that relates the energy export at the root collar to a sum of terms that reflect all fluxes and storage changes along the flow path in thermodynamic terms. We conclude that such a thermodynamic evaluation of root water uptake conveniently provides insights into the impediments of different processes along the entire flow path and explicitly accounting not only for the resistances along the flow path and those imposed by soil drying but especially the role of heterogenous soil water distribution. The results show that least energy needs to be exported and dissipative losses are minimized by a root system if it extracts water uniformly from the soil. This has implications for plant water relations in forests where canopies generate heterogenous input patterns. Our diagnostic in the energy domain should be useful in future model applications for quantifying how plants can evolve towards greater efficiency in their structure and function, particularly in heterogenous soil environments. Generally, this approach may help to better describe heterogeneous processes in the soil in a simple, yet physically-based way.

scholarly journals Comparison Between Phenotypic Confirmatory Test & Double Disc Synergy Test in Detection of Extended Spectrum b-Lactamases Producers Among Gram-Negative Bacilli

2017 ◽  
Vol 15 (2) ◽  
pp. 3-8
Author(s):  
Abu Hena Md Saiful Karim Chowdhury ◽  
Sukumar Nandi ◽  
Mahbubur Rahman ◽  
ASM Ashanul Karim ◽  
Syeda Shanoor Hasina Mamtaz ◽  
...  
Keyword(s):  
Predictive Value ◽  
Low Cost ◽  
Standard Procedure ◽  
Confirmatory Test ◽  
Gram Negative Bacteria ◽  
Bacterial Strains ◽  
Gram Negative ◽  
Extended Spectrum ◽  
Major Interest ◽  
Synergy Test

Background: Extended-Spectrum b-Lactamases (ESBLs) producing bacteria are increasing in number and causing more severe infections because of their continuous mutation and multidrug resistance property which make its treatment difficult. Thus reliable, sensitive and low cost method to detect ESBLs producers, therefore, is of major interest. The present study was undertaken to compare the sensitivity between double disc synergy test & phenotypic confirmatory test to detect ESBLs producing bacteria.Methods: All the isolates were identified by standard procedure of identification & isolated gram-negative bacteria initially screened by Minimum Inhibitory Concentration (MIC) ESBLs breakpoints. Then suspected ESBLs producers are confirmed by double disc synergy test & phenotypic confirmatory test.Results: In the present study, total 176(74.89%) bacterial strains were isolated from 235 samples of wound swab & pus, and urine. Among the isolates, 150(85.23%) were gram-negative and 26(14.77%) were gram-positive bacteria. The gram-negative bacteria were screened for suspected ESBLs & then subjected to confirmatory test where Phenotypic Confirmatory Test (PCT) detected 89(62.68%) and Double Disc Synergy Test (DDST) detected 74(52.11%) ESBL producers. So 15(10.57%) isolates were missed by double disc synergy test. In this study, we determined sensitivity, specificity, positive predictive value & negative predictive value of Phenotypic Confirmatory Test (PCT) were 100%, 77.9%, 83.1% & 100% respectively and those of Double Disc Synergy Test (DDST) were 83.1%, 100%, 100%, and 77.9% respectively.Conclusion: Between these two tests, phenotypic confirmatory test found to be more sensitive procedure than double disc synergy test for the detection of ESBLs producing organisms.Chatt Maa Shi Hosp Med Coll J; Vol.15 (2); Jul 2016; Page 3-8

Bacillus subtilis biofilms characterized as hydrogels. Insights on water uptake and water binding in biofilms

Soft Matter ◽  
2020 ◽  
Vol 16 (26) ◽  
pp. 6180-6190 ◽  
Author(s):  
Nir Ido ◽  
Amir Lybman ◽  
Shahar Hayet ◽  
David N. Azulay ◽  
Mnar Ghrayeb ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Water Uptake ◽  
Bound Water ◽  
Swelling Properties ◽  
Water Binding

Bacillus subtilis biofilms resemble cross-linked hydrogels in their morphology and swelling properties. All the water in these biofilms is bound water. Water binding is mostly related with accumulated solutes.

scholarly journals THE STRUCTURE OF THE COLLODION MEMBRANE AND ITS ELECTRICAL BEHAVIOR

1943 ◽  
Vol 27 (2) ◽  
pp. 77-89 ◽  
Author(s):  
Charles W. Carr ◽  
Karl Sollner
Keyword(s):  
Water Uptake ◽  
Pore Space ◽  
Bound Water ◽  
Weight Increase ◽  
Porous Membranes ◽  
Electrical Behavior ◽  
Volume Changes ◽  
Volume Increase ◽  
Considerable Uncertainty ◽  
Strong Electrolytes

1. The assumption, has generally been made that collodion membranes are rigid and non-swelling in water and aqueous solutions of strong electrolytes, and considerable uncertainty exists as to the manner in which water is taken up by "dried" collodion membranes. In approaching these problems experimentally, the weight and volume changes of collodion membranes when placed in water and when transferred from water to solutions of strong electrolytes were determined. 2. Dried collodion membranes swell reversibly to an appreciable extent when placed in water, the swelling varying from 5 to 11 per cent depending on the brand of collodion. The water uptake and swelling of oxidized collodion is the same as the original unoxidized preparation. 3. The water uptake as determined by the weight increase is larger than could be accounted for by the volume increase, swelling accounting for only 60 to 70 per cent of the water taken up by the membranes. 4. When the "water-wetted dried" collodion membranes were transferred from water to solutions of various strong electrolytes, there was no detectable change in volume. Similarly, when the "porous" membranes were transferred from water to solutions of strong electrolytes, there was no significant volume change. 5. When dried collodion membranes swell in water, some of the water becomes "bound" water, and both intramicellar and intermicellar swelling seem to occur. Therefore, neither the weight increase nor the volume increase nor their difference can be taken as a measure of the true pore space of the membrane. It is concluded that the important problem is not the absolute water content, but how much water in the water-wet membranes is available in useful pathways for the different solutes.

scholarly journals Statistical Structure and Deviations from Equilibrium in Wavy Channel Turbulence

Fluids ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 161 ◽  
Author(s):  
Saadbin Khan ◽  
Balaji Jayaraman
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Outer Layer ◽  
Strong Dependence ◽  
Surface Topology ◽  
Intermittent Flow ◽  
Turbulence Structure ◽  
Near Surface ◽  
Practical Applications ◽  
Major Interest

The structure of turbulent flow over non-flat surfaces is a topic of major interest in practical applications in both engineering and geophysical settings. A lot of work has been done in the fully rough regime at high Reynolds numbers where the effect on the outer layer turbulence structure and the resulting friction drag is well documented. It turns out that surface topology plays a significant role on the flow drag especially in the transitional roughness regime and therefore, is hard to characterize. Survey of literature shows that roughness function depends on the interaction of roughness height, flow Reynolds number, and topology shape. In addition, if the surface topology contains large enough scales then it can impact the outer layer dynamics and in turn modulate the total frictional force. Therefore, it is important to understand the mechanisms underlying drag increase from systematically varied surface undulations in order to better interpret quantifications based on mean statistics such as roughness function. In this study, we explore the mechanisms that modulate the turbulence structure over a two-dimensional (2D) sinusoidal wavy surface with a fixed amplitude, but varying slopes that are sufficiently small to generate only intermittent flow separation. To accomplish this, we perform a set of highly resolved direct numerical simulations (DNS) to model the turbulent flow between two infinitely wide 2D wavy plates at a friction Reynolds number, R e τ = 180 , which represents modest scale separation. We pursue two different but related flavors of analysis. The first one adopts a roughness characterization flavor of such wavy surfaces. The second one focuses on understanding the nonequilibrium near-surface turbulence structure and their impact on roughness characterization. Analysis of the different statistical quantifications show strong dependence on wave slope for the roughness function indicating drag increase due to enhanced turbulent stresses resulting from increased production of vertical velocity variance from the surface undulations.

BOUND WATER, INOSITOL, AND THE INDUCTION OF LAMBDA PROPHAGES BY ULTRAVIOLET LIGHT

1967 ◽  
Vol 13 (3) ◽  
pp. 303-312 ◽  
Author(s):  
S. J. Webb ◽  
M. D. Dumasia
Keyword(s):  
Escherichia Coli ◽  
Ultraviolet Light ◽  
Uv Irradiation ◽  
Maximum Rate ◽  
Bound Water ◽  
Water Molecules ◽  
Prophage Induction ◽  
E Coli ◽  
Escherichia Coli K12 ◽  
Uv Dose

Lysogenic cells of Escherichia coli K12 (λ+) and Escherichia coli M3 (λ59) were held in atmospheres having relative humidities (R.H.) from 30% to 80% and irradiated with 2537 Å ultraviolet light (uv.). The colony-forming ability of both types of cell was destroyed more rapidly at 55% R.H. than at any other level of R.H. With E. coli K12 (λ+) the percentage of cells in which prophage induction occurred increased as the dose of ultraviolet light increased and the maximum number of inductions occurred at 55% R.H. Inositol prevented (λ+) prophage induction but was less effective in doing so at 55% R.H. Desiccation alone induced the (λ59) prophage and subsequent uv. irradiation resulted in the destruction of the prophage. The maximum rate of destruction was found at 55% R.H. Inositol prevented the uv. inactivation of the (λ59) prophage, resulting in an increase in inductions with uv. dose at 30% R.H. The free phages were found to have the same sensitivity to ultraviolet light as the induced prophages but were less protected by inositol.It is proposed that water molecules hold the prophage to or in the host DNA and that ultraviolet light induces the prophage and destroys its integrity by reorientating these water molecules.

scholarly journals Statistical Structure and Deviations from Equilibrium in Wavy Channel Turbulence

2019 ◽  
Author(s):  
Saadbin Khan ◽  
Balaji Jayaraman
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Outer Layer ◽  
Strong Dependence ◽  
Surface Topology ◽  
Turbulence Structure ◽  
Near Surface ◽  
Practical Applications ◽  
Flat Surfaces ◽  
Major Interest

The structure of turbulent flow over non-flat surfaces is a topic of major interest in practical applications in both engineering and geophysical settings. A lot of work has been done in the fully rough regime at high Reynolds numbers where the effect on the outer layer turbulence structure and the resulting friction drag is well documented. It turns out that surface topology plays a significant role on the flow drag especially in the transitional roughness regime and therefore, hard to characterize. Survey of literature shows that roughness function depends on the interaction of roughness height, flow Reynolds number and topology shape. In addition, if the surface topology contains large enough scales then it can impact the outer layer dynamics and in turn modulate the total frictional force. Therefore, it is important to understand the mechanisms underlying drag increase from systematically varied surface undulations in order to better interpret quantifications based on mean statistics such as roughness function. In this study, we explore the mechanisms that modulate the turbulence structure over a two-dimensional (2D) sinusoidal wavy surface with a fixed amplitude, but varying slope. To accomplish this, we model the turbulent flow between two infinitely wide 2D wavy plates at a friction Reynolds number, $Re_{\tau}=180$. We pursue two different but related flavors of analysis. The first one adopts a roughness characterization flavor of such wavy surfaces. The second one focuses on understanding the non-equilibrium near surface turbulence structure and their impact on roughness characterization. Analysis of the different statistical quantifications show strong dependence on wave slope for the roughness function indicating drag increase due to enhanced turbulent stresses resulting from increased production of vertical velocity variance from the surface undulations.

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