Fabrication of Multifunctional Nanostructured Porous Materials

Nanostructured porous materials generally, and nanoporous noble metals specifically, have received considerable attention due to their superior chemical and physical properties over nanoparticles and bulk counterparts. This dissertation work aims to develop well-established strategies for the preparation of multifunctional nanostructured porous materials based on the combination of inorganic-chemistry, organic-chemistry and electrochemistry. The preparation strategies involved one or more of the following processes: sol-gel synthesis, co-electrodeposition, metal ions reduction, electropolymerization and dealloying or chemical etching. The study did not stop at the preparation limits but extended to investigate the reaction mechanism behind the formation of these multifunctional nanoporous structures in order to determine the different factors controlling the nanoporous structures formation. First, gold-silica nanocomposites were prepared and used as a building blocks for the fabrication of high surface area gold coral electrodes. Well-controlled surface area enhancement, film thickness and morphology were achieved. An enhancement in the electrode’s surface area up to 57 times relative to the geometric area was achieved. A critical sol-gel monomer concentration was also noted at which the deposited silica around the gold coral was able to stabilize the gold corals and below which the deposited coral structures are not stable. Second, free-standing and transferable strata-like 3D porous polypyrrole nanostructures were obtained from chemical etching of the electrodeposited polypyrrole-silica nanocomposite films. A new reaction mechanism was developed and a new structural directing factor has been discovered for the first time. Finally, silver-rich platinum alloys were prepared and dealloyed in acidic medium to produce 3D bicontinuous nanoporous platinum nanorods and films with a nanoporous gold-like structure. The 3D-BC-NP-Pt displayed high surface area, typical electrochemical sensing properties in an aqueous medium, and exceptional electrochemical sensing capability in a complex biofouling environment containing fibrinogen. The 3D-BC-NP-Pt displayed high catalytic activity toward the methanol electro-oxidation that is 30 times higher that of planar platinum and high volumetric capacitance of 400 F/cm3. These findings will pave the way toward the development of high performance and reliable electrodes for catalysis, sensing, high power outputs fuel cells, battery-like supercapacitors and miniaturized device applications

STR-829: BEHAVIOR OF GFRP-REINFORCED CONCRETE SQUAT WALLS UNDER SIMULATED EARTHQUAKE LOADING

Steel-reinforced squat walls are used as the main component for earthquake resistance in low-rise structures. Deterioration due to corrosion of steel reinforcement is one of the major challenges facing the construction industry. Furthermore, given the low aspect ratio of squat walls, their behavior is dominated by inelastic shear deformations activated by the yielding of flexural reinforcement. These deformations degrade strength and stiffness with subsequent shear failure, preventing the wall from achieving its flexural capacity, which is a prerequisite for adequate seismic design. Using noncorrodible glass-fiber-reinforced-polymer (GFRP) bars represents an effective method for overcoming corrosion problems. In addition, the available experimental studies on mid-rise shear walls show that GFRP reinforcement can control shear deformation, which is a major problem with steel-reinforced squat walls. Our study was experimentally conducted to investigate the shear-deformation behavior of GFRP-reinforced squat walls. Two full-scale squat walls with an aspect ratio of 1.3 were constructed and tested to failure under quasi-static reversed cyclic lateral loading: one was reinforced with steel bars; the other with GFRP bars. The experimental results show that the GFRP-reinforced wall evidenced significantly enhanced behavior related to ultimate strength, drift ratio, control shear distortion, and mode of failure compared to the steel-reinforced wall

Skeletonized versus pedicled left internal mammary artery harvesting and risk of sternal wound infection after coronary artery bypass surgery

Background: The left internal mammary artery (LIMA) is the gold standard conduit for coronary artery bypass grafting (CABG). There are two harvesting methods, either pedicled or skeletonized. The choice of any technique must consider its complication profile, especially sternal wound infections (SWI). This study aims to evaluate and compare the occurrence of SWI after pedicled and skeletonized LIMA harvesting techniques for CABG. Methods: This prospective observational study included 300 patients who had CABG between 2016 and 2019. We included patients who had pedicled LIMA (n=200) in group 1 and who had skeletonized LIMA (n=100) in group 2. All patients completed a follow-up period of 3 months after CABG. The evaluation during follow-up included: sternal instability, signs of wound infection, temperature, the microbiological study of wound discharge, and chest computed tomography scan. Results: There was no significant differences in age (p = 0.20), male to female ratio (p = 0.43), body mass index (p = 0.12), NYHA I/II (p = 0.50), diabetes mellitus (p = 0.28), ejection  fraction (p= 0.14), and EuroSCORE II (p= 0.09) between groups. No significant difference in cardiopulmonary bypass time (p = 0.24), and cross-clamp time (p= 0.19) between groups. There was a significant increase in the total operating time in skeletonized LIMA group (212.77±75.25 min vs. 190.78±55 minutes, p= 0.004). Skeletonized LIMA was significantly associated lower incidence of SWI than that with pedicled LIMA (4% vs 15.5%, p= 0.003), and non-significantly lower incidence of deep SWI (1% vs 4.5%, p= 0.11). The risk factors for SWI in patients who had pedicled IMA were obesity (OR: 13.06, 95%CI: 3.98-42.89), diabetes mellitus (OR: 10.51, 95%CI: 2.35-46.84), and excessive diathermy (OR: 12.62, 95%CI: 3.93-40.54). Conclusion: Obesity, diabetes, and the use of excessive diathermy for hemostasis may increase the risk of sternal wound infection with pedicled LIMA harvest compared to skeletonized LIMA in patients undergoing CABG

Combined Effect of Seismic-Induced Collision and Soil Stress Irregularity on Seismic Response of Adjacent High-Rise Buildings: Evaluation and Mitigation

Unequal distribution of stresses in the soil underneath the foundations of adjacent buildings represents a great challenge in structural engineering, especially for buildings prone to earthquakes. Another serious problem facing earthquake-prone adjacent buildings is collision, which severely affects the behavior of the buildings and changes the distribution of the soil stresses under the foundations of the buildings. This research investigates seismic responses of adjacent High-Rise Buildings (HRBs) exposed to seismic-induced pounding and impose irregular soil stress distribution considering the Soil-Structure Interaction (SSI) effect. For this purpose, numerical nonlinear dynamic analysis of three-dimensional models of adjacent four HRBs is conducted. To mitigate the exaggerated effect of seismic-induced collision and soil stress irregularity on the seismic response of the adjacent HRBs, three approaches are proposed; improving soil bearing capacity in the highly stressed zone, joining the adjacent HRBs by means of Fluid Viscous Links (FVLs), and combining the two previous approaches. Three-dimensional models of the adjacent 4HRBs group are studied under different earthquakes to examine the above-mentioned three approaches. The combination approach shows promising results in moderating the collision effects; it considerably mitigates the pounding effects between the adjacent HRBs in terms of reducing straining actions and displacements of buildings as well as controlling stresses irregularity in soil under the foundations of such buildings

STR-830: ENHANCING THE DEFORMATION CAPACITY OF CONCRETE SHEAR WALLS REINFORCED WITH GFRP BARS

An experimental study was recently conducted to address the applicability of concrete shear walls entirely reinforced with glass-fiber-reinforced polymer (GFRP) bars and subjected to quasi-static reversed cyclic lateral loading in attaining reasonable strength and drift requirements specified in different codes. The reported test results clearly show that properly designed and detailed GFRP-reinforced concrete (RC) walls could reach their flexural capacities with no strength degradation. The results also demonstrate that the tested walls were able to achieve recoverable and self-centering behavior up to allowable drift limits before experiencing moderate damage and attain a maximum drift comparable to steel-RC walls. The promising results provide impetus for constructing shear walls with GFRP bars and constitute a step toward using GFRP bars in lateral-resisting systems. Since enhancing concrete confinement at the boundary might be a solution in attempting to increase the deformation capacity of GFRP-RC shear walls without significant loss of strength, a series of shear walls were constructed with different reinforcement confinement configurations at the boundary zone. This paper compares the first tested shear wall to a previously reported shear wall (Mohamed et al 2014a). The results show a significant increase in lateral drift and strength of almost 79% and 27%, respectively, by doubling the confinement reinforcement ratio of the boundary. The seismic behavior of the wall was obviously improved, and the deformability level was significantly enhanced

STR-864: PROPOSED STRUT-AND-TIE MODEL FOR CONCRETE DEEP BEAMS REINFORCED WITH FRP BARS

A compiled database of 53 tests of FRP-reinforced concrete deep beams with shear span–depth ratios of less than two was used to evaluate the strut-and-tie models (STM) provided in ACI 318 (2014), CSA S806 (2012), CEB-fib (1999), and JSCE (2007). All provisions were found to be inadequate in calculating the capacity of FRP-reinforced deep beams due to inherent shortcomings in each provision. Hence, a new STM-based procedure for FRP-reinforced deep beams was proposed. The new model incorporates the effect of shear span–depth ratio (a/d), concrete compressive strength (fc’), and tensile strain in the adjoining tie (ε1). The contribution of the web reinforcement on the strut efficiency factor was found to be insignificant. The new model was capable of predicting the ultimate capacity of the compiled FRP-reinforced concrete deep beams with satisfactory conservatism

Mitigation of train-induced vibrations on nearby high-rise buildings by open or geofoam-filled trenches

The vibrations induced by moving trains especially in close distances with high-rise buildings can be destructive. The high technology of wilding rails induced a high train velocity which is associated with high vibrations. The buildings near the railways suffer from the train-induced vibrations. In this paper, a 3D FEM model was constructed to study the train-induced vibrations on a nearby high-rise building (HRB), show its response and investigate the most suitable technique to mitigate the effect of the train-induced vibrations by an open trench or a geofoam-filled trench. Three trench parameters were investigated to enhance the mitigation performance, the distance from the trench to the HRB, the trench depth and the use of either open (empty) trench or geofoam-filled trench. The geofoam-filled trench technique improved the dynamic response of the structure. Thus, trenches filled with geofoam can be considered a protection technique for high-rise buildings constructed near moving trains

Synergistic Physic-Chemical Pretreatment of Lignocellulosic Sugarcane Bagasse via Freezing and Alkaline Processes

This study focuses on employing a hybrid pretreatment approach for lignocellulosic Sugarcane Bagasse (SCB) as a major problematic solid waste. The applied technique depended on SCB physical pretreatment via freezing, followed by chemical hydrolysis using alkaline hydrogen peroxide (AHP) and enzymatic hydrolysis. The changes occurred in macrostructure and the entire lignocellulosic compounds during the pretreatment stages were evaluated. Freezing pretreatment resulted in relatively low glucose yield and saccharification ratio at -20 °C for 2 h of 307.52 mg/gm native SCB and 48.5%, respectively. Further AHP pretreatment was performed for the frozen-pretreated SCB at -20 °C and 2 h with assistance of Box–Behnken Design response surface methodology (RSM). The investigated key parameters were H2O2 concentration (3, 5.5 and 8 %v/v), temperature (25, 42.5 and 60 °C) and pretreatment duration (1, 3 and 5 h). The results revealed that the statistical modelling was able to predict the response of glucose yield and TRS production with R2 = 0.8221 and 0.8814, respectively. Applying the optimization tool of RSM, the optimum predicted values of glucose yield and TRS production were (886.51 mg/gm native SCB and 1.44 mg/mL), respectively; confirmed by the experimental analysis (898.5 mg/gm native SCB and 1.32 mg/mL), respectively. The coincided saccharification ratio was 97.5%. These results were obtained at H2O2 of 3 % (v/v), 56.93 °C and 1 h which were 4.32 and 2.01 times higher than that obtained during the freezing pretreatment phase for glucose yield and saccharification ratio, respectively

Prevalence of cesarean section on demand in Assiut Governorate, Egypt

Background: The current study aims to evaluate the prevalence of CS on demand in Women's health hospital, Assiut University and Abnob Central Hospital in Assiut Governorate, Egypt.Methods: A cross sectional study conducted in Assiut Women Health Hospital and Abnob central hospital from January 2017 to December 2017. The total number of cesarean section done was 180 cases and the number of CS on demand was 64 (35.6%). The demographic data were collected by one of the study investigators. Women were asked about the causes of requesting CS before surgery.Results: The study group was 64 women with age ranging from 18-40 years old, 40 primipara and 24 multipara. Of those 24 women, 21 of them previously delivered vaginally and only 3 women delivered by emergency CS. Twenty- six women had a history of previous abortion. Fear of pain was the main cause for CS on demand in the whole study participants (57.8%). In primipara, the main cause for requesting CS is fear of pain in 62.5% of participants followed by fear on the baby in 45 % of women. On the other hand, in multipara, the main cause for CS on demand was bad history of previous experience (60%) followed by fear of pain in 50% of cases. There was statistical significant difference between both groups in only two causes; fear of pelvic floor injuries (50% in multipara vs. 20% in primipara, p=0.02) and bad history of previous experience (60% in multipara vs. 0% in primipara, p=0.001). Other causes were not statistically different.Conclusions: The incidence of cesarean sections performed on request without medical indications is rising. The reasons for this are not only for perceived medical benefit, but also due to social, cultural, and psychological factors

Effect of salinity and sodicity stresses on physiological response and productivity in Helianthus annuus

Soil salinity and sodicity (alkalinity) are serious land degradation issues worldwide that are predicted to increase in the future. The objective of the present study is to distinguish the effects of NaCl and Na2CO3 salinity in two concentrations on the growth, lipoxygenase (LOX) activity, membrane integrity, total lipids, yield parameters and fatty acids (FAs) composition of seeds of sunflower cultivar Sakha 53. Plant growth, LOX activity and malondialdehyde (MDA) content were reduced by salts stresses. On the contrary, salinity and alkalinity stress induced stimulatory effects on membrane permeability, leakage of UV-metabolites from leaves and total lipids of sunflower shoots and roots. Crop yield (plant height, head diameter, seed index and number of seeds for each head) that is known as a hallmark of plant stress was decreased by increasing concentrations of NaCl and Na2CO3 in the growth media. Fatty acid methyl esters (FAME) composition of salt-stressed sunflower seeds varied with different levels of NaCl and Na2CO3