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Improving the Performance of Superabsorbent Polymers as Internal Curing Agents in Concrete: Effects of Novel Composite Hydrogels on Microstructure and Hydration of Cementitious SystemsBaishakhi Bose (11199993) 29 July 2021 (has links)
<p>Superabsorbent polymer (SAP)
hydrogel particles have been used as internal curing agents in concrete mixes
as they are capable of absorbing and subsequently releasing large amounts of
water. This reduces autogenous shrinkage during early stages of hydration. The
size, shape, and composition of the hydrogel particles can be controlled during
the synthesis, hence providing the opportunity to custom synthesize these internal
curing agents to elicit desired structure-property relationships. Utilization
of optimized dosage and formulation of SAP has the potential to improve the
microstructure, durability, and strength of internally cured concrete. </p>
<p>The first study focuses on the
synthesis and application of novel composite hydrogel particles as internal
curing agents in cementitious mixes. Composite polyacrylamide hydrogel
particles containing two different amorphous silica–either nanosilica or silica
fume–were used to investigate whether the internal curing performance of
hydrogel particles could be enhanced. The dosage and type of silica,
crosslinker amount were varied to identify the composite polyacrylamide
hydrogel particle composition that provides optimum benefits to internally
cured cementitious systems. The synthesized hydrogels were characterized by
means of absorption capacity tests, compositional and size analysis. The
beneficial impacts of the addition of composite hydrogels on cement paste
microstructure are highlighted, including the preferential formation of cement
hydration products (such as portlandite) within the hydrogel-induced voids that
appeared to be influenced by the composition of the hydrogel particles. The
interrelationship between extent of hydration, size of hydrogel voids, and
void-filling with hydration products was found to strongly influence mechanical
strength and is thus an important structure-property relationship to consider
when selecting hydrogels for internal curing purposes. This study informs the
design of composite hydrogel particles to optimize performance in cementitious
mixes. Additionally, it provides a novel means of incorporating other commonly
used admixtures in concrete without facing common challenges related to
dispersion and health hazards.</p>
<p>The second study focuses on the
utilization of two retarding admixture-citric acid and sucrose-to custom
synthesize composite polyacrylamides to investigate whether the composite
hydrogels could delay hydration of cement paste. Isothermal calorimetry
analysis results showed that composite sucrose-containing polyacrylamide
hydrogel particles were successfully able to retard main hydration peak of
cement paste, beyond the retardation capabilities of the pure polyacrylamide
hydrogels. Thus, this study provides avenues of exploring the utilization of
common admixtures to formulate novel composite hydrogels that imparts specific
properties to cementitious systems.</p>
<p>In another study, SAP formulated
by admixture industries were used to investigate the feasibility of internal
curing of bridge decks and pavement patches with SAP particles. The
microstructure and early age hydration properties of SAP-cured cementitious
systems were studied. Mitigation of microcracks in the matrix, along with
portlandite growth in SAP voids, were observed in SAP-cured mortars. Presence
of SAP also mitigated autogenous shrinkage and improved early age hydration as
observed by isothermal calorimetry analysis. This thesis highlights some of the
beneficial impacts of SAP-cured cementitious systems, and the potential to
harness those benefits in large-scale applications of SAP-cured concrete.</p>
<br>
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Ultrafast Collective Dynamics of Water-Protein InteractionsHouston, Patrick R. January 2020 (has links)
No description available.
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Secondary Dormancy and Summer Conditions Influence Outcomes in the Pyrenophora semeniperda - Bromus tectorum PathosystemHawkins, Katie Karen 08 July 2014 (has links) (PDF)
Variable mortality of Pyrenophora semeniperda–infected Bromus tectorum seeds has been referred to as a “race for survival.” Dormant seeds are highly susceptible to P. semeniperda infection. While much is known about primary dormancy little is known about secondary dormancy in B. tectorum seeds. Dormancy status is not the only variable determining outcomes within the Bromus - Pyrenophora pathosystem. Varying temperature and intermittent hydration may strongly influence germination outcomes of B. tectorum in the presence of P. semeniperda. While it has long been assumed that B. tectorum seeds are infected by P. semeniperda in the fall it was recently suggested that seeds may be infected in the summer; however, there is little evidence to support this. To further characterize the Pyrenophora semeniperda - Bromus tectorum pathosystem two studies were conducted to address the following: (1) characterization of secondary dormancy in B. tectorum seeds and (2) summer interactions between host and pathogen after summer inoculation. Studies were conducted using dormant and/or non-dormant B. tectorum (along with B. rubens in one study) seeds and two strains of P. semeniperda. Study one used laboratory and field experiments to characterize secondary dormancy in B. tectorum seeds in terms of temperature (0.5-20°C), and water potential (-2.0-0 MPa). Data was used in repeated probit regression analysis to determine hydrothermal parameters (ψb(50), σψb, θHT) for secondary dormancy induction and loss. In the second study seeds were inoculated with one of two strains of P. semeniperda then exposed to intermittent hydration or dry storage at warm temperatures (30-60°C). After treatment seeds were rehydrated and outcomes observed. Optimum conditions for secondary dormancy induction were incubation at -1.0 MPa at 5°C. Seeds were likely to enter secondary dormancy through the cold winter months indicated by an increase or more positive ψb(50), while a decrease or more negative ψb(50) is associated with dormancy loss which is generally observed in the hot, dry summer months. When seeds were inoculated in the summer they only escaped death when summer conditions were ideal for after-ripening which allowed them to germinate rapidly under favorable autumn conditions. However, the pathogen caused high seed mortality no matter the treatment when disease progression advanced enough to inhibit seed germination. Thus this research shows that in areas with frequent summer rain storms, it would be highly advantageous to apply P. semeniperda as a biocontrol on seeds at maturity.
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Effects of Various Molecules on the Structure and Dynamics of Lipid Membranes / Molecules in membranes: Where they are, what they doToppozini, Laura 11 1900 (has links)
In my time at the Laboratory of Membrane and Protein Dynamics at McMaster University, it has been our goal to investigate the fundamental properties of model membranes and how some common membrane molecules, namely water, ethanol, and cholesterol, interact with the bilayer. Our studies employ highly-oriented, solid-supported membranes in order to extract unambiguous structural information perpendicular to and in the plane of the membranes, with the exception of the hydrated powder samples used in probing the effects on ethanol. Both X-ray and neutron scattering were employed to investigate the structural properties of the membranes and neutron scattering was used to infer the dynamical properties.
A variety of neutron scattering techniques were used to determine the properties of hydrated
lipid bilayers, as described in the first two publications listed. Instruments including a neutron
backscattering spectrometer, reflectometer, and time-of-flight spectrometer were used to observe bilayer structure, lipid/water coupling, and water diffusion. We found that hydrated, solid-supported single-bilayers showed no strong coupling between hydration water and lipid tails and the out-of-plane structure of stacked fluid bilayers as well as the anisotropic and anomalous behaviour of hydration water compared to bulk water.
Both X-ray and neutron scattering experiments were done to determine the effect of a 2mol%
concentration of ethanol on a hydrated lipid powder. X-ray scattering was used to determine
the structural changes due to the addition of ethanol and the location of ethanol within the bilayer.
This was accomplished by determining areas of increased electron density in the head group and among the acyl tails. The presence of ethanol also attributed to a decrease in lateral lipid diffusion constant in the gel phase, while no significant change was found in fluid bilayers. In the final study outlined in this thesis, the result of a 32.5% concentration of cholesterol in
a hydrated, fluid phospholipid membrane is discussed. Coarse-grained molecular simulations and measurements of the lateral structure of the membrane via neutron spectrometry were able to determine the heterogeneous nature of the liquid-ordered phase and the structure of each of the domains in the membrane.
The following thesis will introduce model membranes, their relevant components and the scattering of X-rays and neutrons from such matter. Next, experimental techniques, sample constituents, sample preparations, and instruments used in experiments will be described. Then, each study will be introduced and discussed which will showcase the progress made in the field of model membranes.
Lastly, an overview of the studies will lead in to future directions for each model system in terms of suggested experiments and general path. / Thesis / Doctor of Philosophy (PhD)
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Study of Effective Use of Sugarcane Residue as Eco-friendly Construction Materials for Disaster Prevention Structures / 環境に優しい建設材料としてのサトウキビ廃材の防災構造物への利用Ribeiro, Bruno 23 March 2021 (has links)
学位プログラム名: 京都大学大学院思修館 / 京都大学 / 新制・課程博士 / 博士(総合学術) / 甲第23347号 / 総総博第20号 / 新制||総総||4(附属図書館) / 京都大学大学院総合生存学館総合生存学専攻 / (主査)教授 山敷 庸亮, 教授 山本 貴士, 教授 寶 馨, 教授 齋藤 敬 / 学位規則第4条第1項該当 / Doctor of Philosophy / Kyoto University / DFAM
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APPLICATION OF PROCESS ANALYTICAL TECHNOLOGY TO PHARMACEUTICAL PROCESSESHAUSMAN-MANNING, DEBRA SUE 23 May 2005 (has links)
No description available.
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Ultrafast Protein Hydration Dynamics and Water-Protein InteractionsYang, Jin January 2016 (has links)
No description available.
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Reactivation Mechanism Studies on Calcium-Based Sorbents and its Applications for Clean Fossil Energy Conversion SystemsYu, Fu-Chen 17 March 2011 (has links)
No description available.
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Ultrafast Spectroscopic Study of Hydration and Conformational Dynamics in CalmodulinCraigo, Kevin Alan 13 September 2011 (has links)
No description available.
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Short-term effects of selected barrier creams on skin barrier function / Amanda VermaakVermaak, Amanda January 2014 (has links)
Background: Barrier creams are applied to the surface of the skin to form a barrier that aims to prevent the penetration of irritants and allergens through the skin surface. Several inconsistencies and controversies exist in literature regarding the effect that barrier creams may have on skin barrier function. Various skin surface parameters are used to evaluate the effect that the barrier creams have on skin barrier function. These parameters include transepidermal water loss (TEWL), skin hydration and skin surface pH. Total skin thickness may be assessed as a variable on its own. Differences may exist in skin surface parameters when comparing African participants with Caucasian participants.
Aim: The specific aim of this research was to evaluate the short-term1 effects of selected barrier creams on skin barrier function.
Note 1: The words short-term are used in this study as each barrier cream is only tested over a period of 8 hours and not tested over a long term period of months or years.
Method: Forty two non-smoking participants were included and tested in this study, of which 21 were African and the rest Caucasian. TEWL, skin hydration and skin surface pH were used to evaluate the differences in the effect of two different barrier creams (Reinol Solvgard and Momar Chex) on skin barrier function. TEWL was measured by making use of a closed chamber Vapometer (Deflin Technology Ltd., Kuopio, Finland), skin hydration using a Corneometer® CM 825 and skin surface pH using a pH meter probe (Courage and Khazaka Electronic Kӧln, Germany). A micro-pipette was used to drip a standard volume of 20 μl of ultrapure water on the skin surface before the researcher placed the pH meter probe onto the skin surface. Total skin thickness was measured by making use of ultrasound (Ultrascan 22 - TBS0061B) (Courage and Khazaka Electronic Kӧln, Germany). Three consecutive measurements were taken on the mid-forearm and the palm of the experimental arm. After baseline values were measured, 5 ml of the selected barrier cream was applied to the experimental arm. The barrier cream (selected for the day) was reapplied after 2, 4 and 6 hours and measurements were taken every 2, 4, 6 and 8 hours. The total skin thickness was measured at time zero and at 8 hours.
Results:
TEWL: For both barrier creams, statistical significant differences (p ≤ 0.05) were found between TEWL on the palms of African participants and Caucasian participants.
Skin hydration: Statistically significant differences (p ≤ 0.05) were obtained with regard to mid-forearm skin hydration when comparing Reinol Solvgard with Momar Chex (this was applicable to both racial groups). A statistically significant difference (p ≤ 0.05) was obtained with regard to mid-forearm skin hydration when comparing African participants with Caucasian participants (this was only applicable to Reinol Solvgard). Statistical significant differences (p ≤ 0.05) were obtained with regard to skin hydration palm when comparing Reinol Solvgard with Momar Chex (this was applicable to both racial groups). Statistically significant differences (p ≤ 0.05) were obtained with regards to skin hydration palm when comparing African participants with Caucasian participants (this was applicable to both barrier creams).
Skin surface pH: A statistically significant difference (p ≤ 0.05) was obtained with regard to pH of the mid-forearm when comparing Reinol Solvgard with Momar Chex (this was applicable to only the African participants). A statistical significance (p ≤ 0.05) was obtained with regards to skin surface pH mid-forearm when comparing African participants with Caucasian participants (this was applicable to Momar Chex barrier cream only). A statistically significant difference (p ≤ 0.05) was obtained with regards to the pH of the palm when comparing Reinol Solvgard with Momar Chex (this was only applicable to the African racial group).
Conclusion: Using skin surface parameters, it can be concluded that Momar Chex barrier cream elicited more positive effects on skin barrier function than Reinol Solvgard barrier cream. This may be ascribed to the fact that both barrier creams lowered TEWL (positive effect), Reinol Solvgard lowered skin hydration (negative effect) whereas, Momar Chex increased the skin hydration (positive effect) and both barrier creams increased skin surface pH (negative effect). Furthermore, the objectives of this study were reached as (a) short-term effects on skin surface parameters were identified between African versus Caucasian participants, (b) significances were observed between the two barrier creams (Momar Chex and Reinol Solvgard) by making use of skin surface parameters and (c) general increases and or decreases were observed in skin surface parameters over a short term period of 8 hours. / MSc (Occupational Hygiene), North-West University, Potchefstroom Campus, 2015
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