Effect of Morphologically Controlled Hematite Nanoparticles on the Properties of Fly Ash Blended Cement

Several types of hematite nanoparticles (α-Fe2O3) have been investigated for their effects on the structure and properties of fly ash (FA) blended cement. All synthesized nanoparticles were found to be of spherical shape, but of different particle sizes ranging from 10 to 195 nm depending on the surfactant used in their preparation. The cement hydration with time showed 1.0% α-Fe2O3 nanoparticles are effective accelerators for FA blended cement. Moreover, adding α-Fe2O3 nanoparticles in FA blended cement enhanced the compressive strength and workability of cement. Nanoparticle size and size distribution were important for optimal filling of various size of pores within the cement structure.This research was funded by The Thailand Science Research and Innovation (TSRI) cooperated with Siam Research and Innovation Co., Ltd., Thailand, for the “Research and Researcher for Industry (RRI) Fund”, contract number PHD 59I0071, which provides for Pantharee Kongsat for her Ph.D. study and research. Open Access fees paid for in whole or in part by the University of Oklahoma Libraries.Ye

Elongational Stresses and Cells

Fluid forces and their effects on cells have been researched for quite some time, especially in the realm of biology and medicine. Shear forces have been the primary emphasis, often attributed as being the main source of cell deformation/damage in devices like prosthetic heart valves and artificial organs. Less well understood and studied are extensional stresses which are often found in such devices, in bioreactors, and in normal blood circulation. Several microfluidic channels utilizing hyperbolic, abrupt, or tapered constrictions and cross-flow geometries, have been used to isolate the effects of extensional flow. Under such flow cell deformations, erythrocytes, leukocytes, and a variety of other cell types have been examined. Results suggest that extensional stresses cause larger deformation than shear stresses of the same magnitude. This has further implications in assessing cell injury from mechanical forces in artificial organs and bioreactors. The cells’ greater sensitivity to extensional stress has found utility in mechanophenotyping devices, which have been successfully used to identify pathologies that affect cell deformability. Further application outside of biology includes disrupting cells for increased food product stability and harvesting macromolecules for biofuel. The effects of extensional stresses on cells remains an area meriting further study.Open Access fees paid for in whole or in part by the University of Oklahoma Libraries.Ye

Effect of Injection Rate and Post-Fill Cure Pressure on Properties of Resin Transfer Molded Disks

The effects of flow rate andpost-fill cure pressure, i.e., packing pressure, on the mechanical properties of resin transfer molded disks are experimentally investigated. An experimental molding setup is constructed to fabricate fiber-reinforced, center-gated, disk-shaped composite parts. Disks are molded at different flow rates and packing pressures in order to observe the effects of these parameters on the mechanical properties andvoidcontent of the final parts. Specimens are cut from three different locations in the molded disks for testing. Specimens from the first two locations are tensile testedto obtain strength and stiffness properties, and the third location is usedfor microscopic analysis to determine void content and void properties. Increased injection rate is found to reduce both the strength and stiffness of the molded parts due to more voids induced by the faster moving fluidfront. Packing pressure is also foundto have a significant effect on specimen properties. At higher packing pressures fewer voids and improved strength andstiffness are observed. Mechanical properties are correlatedwith total void fraction for disks molded at different packing pressures. Exponential decrease in both tensile strength andelastic modulus is observedwith increasing voidfraction. Doubling the voidvolume fraction from 0.35 to 0.72% results in a 15% decrease in strength and a 14% decrease in stiffness. The results demonstrate that selection of suitable injection rate and addition of packing pressure to resin transfer molding (RTM) process can improve mechanical properties of molded parts considerably.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline

Performance of Glass Woven Fabric Composites with Admicellar-Coated Thin Elastomeric Interphase

Adequate stress transfer between the inorganic reinforcement and surrounding polymeric matrix is essential for achieving enhanced structural integrity and extended lifetime performance of fiber-reinforced composites. The insertion of an elastomeric interlayer helps increase the stress-transfer capabilities across the fiber/matrix interface and considerably reduces crack initiation phenomena at the fiber ends. In this study, admicellar polymerization is used to modify the fiber/matrix interface in glass woven fabric composites by forming thickness-controlled poly(styrene-co-isoprene) coatings. These admicellar interphases have distinct characteristics (e.g., topology and surface coverage) depending on the surfactant/monomer (S/M) ratios used during the polymerization reaction. Overall, the admicellar coatings have a positive effect on the mechanical response of resin transfer molded (RTM), E-glass/epoxy parts. For instance, ultimate tensile strength (UTS) of composites with admicellar sizings improved 50 to 55% over the control desized samples. Interlaminar shear strength (ILSS) also showed increases ranging from 18 to 38% over the same control group. Interestingly, the flexural properties of these composites proved sensitive to the type of interphase formed for various admicellar polymerization conditions. Higher surface coverage and film connectedness in admicellar polymeric sizings are observed to enhance stress transfer at the interfacial region.Ye

Porosity Reduction in the High-Speed Processing of Glass-Fiber Composites by Resin Transfer Molding (RTM)

High-speed processing is essential to achieve lower production cost in the fabrication of fiber-reinforced composites with the current liquid molding practices. A major consequence of increasing the resin injection velocity is the formation of defects such as voids and dry regions that decrease the load-bearing capability of the composite. Void formation mechanisms and analytical predictions of the detrimental effect of porosity on the structural integrity of molded parts have been studied extensively. In contrast, knowledge of void removal strategies is very limited. In this investigation, various postfill pressure levels were applied to disk-shaped random-mat glass/epoxy parts molded at high volumetric flow rates as a method to reduce their voidage content. Quantitative image analysis over cross-sections cut from these composites revealed that significant changes in porosity concentration take place with the postfill pressure. For instance, overall void content dropped more than 70% with the application of a postfill pressure as low as 300 kPa. Other important void morphometry characteristics such as void shape, size, and spatial distribution could also be manipulated by this method. As the packing pressure increases, large voids gradually disappear, and at the same time, the small circular voids are mobilized towards radial locations near the vents. In addition to this spatial voidage gradient in the radial direction, voidage gradient also exists through the specimen thickness. It seems that higher front velocities promote the appearance of secondary flow phenomena inside the mold cavity (e.g. microfountain flow), which may explain why more voids tend to concentrate at the surface of the specimen irrespective of the postfill pressure level reached inside the mold.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline

Reynolds Stresses and Hemolysis in Turbulent Flow Examined by Threshold Analysis

Use of laminar flow-derived power law models to predict hemolysis with turbulence remains problematical. Flows in a Couette viscometer and a capillary tube have been simulated to investigate various combinations of Reynolds and/or viscous stresses power law models for hemolysis prediction. A finite volume-based computational method provided Reynolds and viscous stresses so that the effects of area-averaged and time-averaged Reynolds stresses, as well as total, viscous, and wall shear on hemolysis prediction could be assessed. The flow computations were conducted by using Reynolds-Averaged Navier-Stokes models of turbulence (k-ε and k-ω SST) to simulate four different experimental conditions in a capillary tube and seven experimental conditions in a Couette viscometer taken from the literature. Power law models were compared by calculating standard errors between measured hemolysis values and those derived from power law models with data from the simulations. In addition, suitability of Reynolds and viscous stresses was studied by threshold analysis. Results showed there was no evidence of a threshold value for hemolysis in terms of Reynolds and viscous stresses. Therefore, Reynolds and viscous stresses are not good predictors of hemolysis. Of power law models, the Zhang power law model (Artificial Organs, 2011, 35, 1180–1186) gives the lowest error overall for the hemolysis index and Reynolds stress (0.05570), while Giersiepen’s model (The International journal of Artificial Organs, 1990, 13, 300–306) yields the highest (6.6658), and intermediate errors are found through use of Heuser’s (Biorheology, 1980, 17, 17–24) model (0.3861) and Fraser’s (Journal of Biomechanical Engineering, 2012, 134, 081002) model (0.3947)

Stain Resistance of Cotton Fabrics before and after Finishing with Admicellar Polymerization

Environmental concerns related to perfluoroctanoic acid (PFOA) led to a re-examination of the methods for imparting stain resistance and stain repellency to textiles. Non-PFOA fluoropolymer finishes have been formed on cotton knits by admicellar polymerization, a surface analogue of emulsion polymerization. Fabric samples were characterized by a drop test, contact angle measurements, SEM, elemental analysis and durability studies. Stain resistance and stain release properties were assessed by reflectance and AATCC tests with results comparing favorably with swatches from commercially available garments. Admicellar polymerization enabled the formation of durable finishes that exhibited high performance in stain resistance and stain repellency

Sublethal Damage to Erythrocytes during Blood Flow

Mechanical circulatory support (MCS) devices are designed to perform the functional needs of organs and to meet clinical hemocompability criteria. Critical complications have been reported with their long-term use such as thrombosis, anemia and gastrointestinal bleeding. Damage to red blood cells (RBCs), which occurs with nonphysiological blood flow conditions such as contact with foreign surfaces, high shear stress, and turbulence, is a major problem for the design and development of these systems. Even in the absence of hemolysis, cardiovascular devices (CAD) still cause cell injury and shortened RBC lifespans. This review summarizes various effects that occur to erythrocytes exposed to supraphysiological but sublethal stresses

Sublethal Damage to Erythrocytes during Blood Flow

Mechanical circulatory support (MCS) devices are designed to perform the functional needs of organs and to meet clinical hemocompability criteria. Critical complications have been reported with their long-term use such as thrombosis, anemia and gastrointestinal bleeding. Damage to red blood cells (RBCs), which occurs with nonphysiological blood flow conditions such as contact with foreign surfaces, high shear stress, and turbulence, is a major problem for the design and development of these systems. Even in the absence of hemolysis, cardiovascular devices (CAD) still cause cell injury and shortened RBC lifespans. This review summarizes various effects that occur to erythrocytes exposed to supraphysiological but sublethal stresses

The Applicability of a Drop Penetration Method to Measure Contact Angles on TiO2 and ZnO Nanoparticles

In this study, six solvents (water, diiodomethane, bromonaphthalene, formamide, ethanol and ethylene glycol) were examined for three nanoparticle substrates, zinc oxide and titanium dioxide (21 nm and 100 nm), with the goal of assessing the suitability of a modified drop penetration method (DPM) for orders of magnitude smaller particles. Nanoparticles were compressed into flat discs and the solvent dropped on the surface while the image with time was recorded. Contact angles were in reasonable agreement with literature over the range of 20–80°, but failed to provide acceptable results for surface energy components. It was necessary to eliminate certain solvents and substrates not meeting the selection criteria