Anti-Freeze Double Network Hydrogels

Three polyethylene glycol (PEG) based crosslinkers with repeat unit nominal weights of 62.1, 200, and 400 g/mol in agar/PAM double network (DN) hydrogels were used to study the effect of different crosslinkers on thermal and mechanical properties. Using the one-pot synthesis method, hydrogels with the PEG crosslinkers or methylene-bis-acrylamide (MBAA) were made via sol-gel transition for formation of agar network, and photopolymerization of the PAM network using Irgacure 2959 as photo initiator. Tensile and compression tests were performed on as prepared, swollen, and swollen & cooled specimens of each hydrogel. Freezing time and thermal imaging were performed in -20 °C freezer, and thawing at room temperature followed freezing in -60 °C freezer. MBAA then PEG based crosslinkers with increasing molecular weight increased freezing time (normalized 1 hr, 1.9 hr, 2.9 hr, 3.8 hr) and decreased heat conductivity which may result from London dispersion forces, crosslinker hydrogen bonds with water, and porosity. Under tension and compression, PEG400-INA and EGINA based crosslinker experienced better trends from colder temperatures on mechanical properties than MBAA. They also experienced decreased swelling ratios of 6.11, 5.65, 5.20, 5.75 from MBAA to PEG400-INA when compared to that of PAM SN 11.69. This is work will inspire researchers to optimize PEG based crosslinkers in as prepared hydrogels, understand their anti-freezing mechanisms, and find applications in low temperature environments such as supercapacitors, and deep ocean

Field Armies and Fortifications in the Civil War: The Eastern Campaigns, 1861-1864

Effective earthworks Proper fortifications multiplied force If you don\u27t know what is meant by mamelon\u27 and ravelin\u27 then immediately refer to the Glossary of this book before proceeding. It is the best place to start if you are not conversant with the terms of field fortificatio...

Shanks: The Life and Wars of General Nathan G. Evans, CSA

Military man West Point cadet becomes outstanding Confederate officer Shanks is a well-researched book about General Nathaniel G. Evans, a lesser known Confederate leader. The text covers not only his years of service as a combat leader in the service of his home state and...

Bridging Deep South Rivers: The Life and Legend of Horace King

Many rivers to cross Slave pioneers architectural design and social equality The book\u27s title is a little misleading. Picking it up I expected to find a volume on the design and construction of bridges in the Southern United States during the period centered on the War Between th...

Effect of Vertically Heterogeneous Soil on Simulated Water Storage and Surface Energy

The global effects of climate change and policy decisions are simulated, in part, by land surface models; yet, the models often use incomplete soil information that may result in unreliable estimates of soil water storage and surface energy fluxes. The objectives of this study were to: 1) quantify the impact of better representation of vertical heterogeneity of soil characterization on simulated soil water storage and surface energy fluxes; and 2) to simulate the effect of abrupt soil textural change from sandy to clayey (i.e. presence of argillic horizons) on patterns of simulated surface energy fluxes. In this study, the Root Zone and Water Quality Model: Version 2 (RZWQM2) and measurements of soil moisture from soil in Palestine, TX (loamy, siliceous, semiactive, thermic Arenic Plinthic Paleudult) and Bronte, TX (fine loamy, mixed, superactive, thermic Typic Paleustalf) were used. The results showed that more accurate representation of vertical soil textural heterogeneity and hydraulic parameters improved the predictions of soil water storage compared to measurements. Simulations under an abrupt texture discontinuity, such as sandy over clayey soil, increased the magnitude of differences in latent and sensible heat partitioning. Additionally, accounting for a simulated argillic horizon revealed a predictable pattern of simulated latent heat fluxes as a function of claypan and rooting depths, where the interquartile range of latent heat fluxes: 1) shift to a maximum for claypans above the rooting depth, 2) plateau until the rooting depth, 3) shift to a minimum for claypans below the rooting depth, and 4) steadily increase shift with diminishing returns after the minimum has been reached. This study showed that accurately simulating vertical changes in soil texture with depth changed estimates of plant available water and improved soil water prediction accuracy. Subsequently, simulated ranges of latent heat fluxes were also affected. Given improved reliability in simulation of soil water and latent heat fluxes in land surface models, the representation of soil vertical heterogeneity and hydraulic parameters are anticipated to improve the performance of land surface models

Balks And Stringers: A Look At The Technology And Terminology Of Floating Bridges

The mission of combat engineers in today\u27s army encompasses four tasks: mobility, counter-mobility, survivability, and general engineering. When undertaking offensive operations, engineers sustain mobility by ensuring that the force in the field can maneuver as its commander desires even in the face...

Engineering Combat: The Battlefield As Showcase For New Technology

In Trial by Fire, Charles Ross presents an interesting book covering the applications of science and technology in the Civil War. Ross addresses the applications of existing technology to support combat forces and the applications of new technology to combat. While the book is not an exhausti...