CHARACTERIZATION OF THE INTERFACIAL BEHAVIOR OF HYBRID FIBER-STEEL LAP CONNECTIONS FASTENED BY STEEL ON FRP ANCHORS

Fiber reinforced polymers (FRP) are extensively used in several engineering fields due to their superior properties. In structural engineering applications, fiber polymers have been recently used for retrofitting and strengthening of existing structures. A common technique for strengthening steel structures involves bonding FRP composites to targeted steel elements. However, bonding practices and researches revealed undesirable brittle failure of the adhesive at the FRP-steel interface. A recent research program conducted at UAE University validated the effectiveness of using mechanically fastened hybrid FRP (HFRP) laminates in strengthening steel beams. Outcomes of the research program revealed that the fastening technique could provide a good alternative to overcome the unfavorable brittle failure of bonded FRP composites. In addition, the study was enlightening and showed promising results in terms of both yield and ultimate load capacities of the strengthened steel beams. However, a limited range of fastening parameters was examined in the above mentioned research program. The current research study is motivated by the need to investigate the influence of wider range of fastening parameters and geometrical configurations on the interfacial behavior of fastened HFRP-steel connections. An extensive experimental program was carried out on 62 fastened connections on two phases. In the first phase, the effect of different number of washers-per-bolt, clamping torque, bolt-hole diameter and bolt spacing were investigated on connections formed using steel bolts. While the second phase was conducted using FRP anchors to examine the effect of fastener type and diameter along with the sheared edge distance on the performance of the connections. Test results recommended to snug-tight the steel bolts after placing them in standard hole-diameters with the use of 2 washers-per-bolt. Bolt spacing was proven to have insignificant effect on both failure modes and load carrying capacity of the HFRP-steel connections. The study also suggested the use of FRP anchors with 13 mm diameter with a sheared edge distance that is three times the hole-diameter for optimal performance in terms of ductility and load carrying capacity. Recorded experimental measurements were utilized to develop nonlinear load-slip models which were integrated in developing nonlinear 3D finite element (FE) models using ANSYS software. FE models were used to simulate the behavior of the fastened connections and to accurately predict their load carrying capacity. Numerical predictions were in excellent agreement with the experimental findings which verified the accuracy of the proposed nonlinear load-slip models

Analytical and experimental study of electrical conductivity in the lithium tantalate nonstoichiometric structure

We have been interested to experimental and analytical studies of ionic conductivity of nonstoichiometric LiTaO3 solid solutions. Theoretical approach combined with lithium and tantalate vacancy models has been performed. A comparative study between the calculated and measured values is presented taking into account the temperature and composition effects on the conductivity.We have been interested to experimental and analytical studies of ionic conductivity of nonstoichiometric LiTaO3 solid solutions. Theoretical approach combined with lithium and tantalate vacancy models has been performed. A comparative study between the calculated and measured values is presented taking into account the temperature and composition effects on the conductivity

Glibenclamide Mini-tablets with an Enhanced Pharmacokinetic and Pharmacodynamic Performance.

In an attempt to decrease the dose, anticipated side effects, and the cost of production of glibenclamide, GLC, a potent oral hypoglycemic drug, the enhancement of the dissolution and hence the oral bioavailability were investigated. Adsorption and co-adsorption techniques using carriers having a very large surface area and surface active agents were utilized to enhance the drug dissolution. Moreover, the Langmuir adsorption isotherms were constructed to identify the type and mechanism of adsorption. The optimized formulation showing the highest in vitro release was compressed into mini-tablet to facilitate drug administration to elderly patients and those having swallowing difficulties. The produced mini-tablets were tested for their mechanical strength and in vitro release pattern. In addition, the pharmacodynamic and pharmacokinetic studies in New Zealand rabbits were performed using the optimized mini-tablet formulation. Mini-tablets containing GLC co-adsorbate with Pluronic F-68 and Laponite RD showed 100 ± 1.88% of GLC released after 20 min. Pharmacodynamic studies in rabbits revealed significantly higher (p ≤ 0.05) hypoglycemic effect with the optimized mini-tablets at a lower GLC dose compared to mini-tablets containing the commercial GLC dose. Moreover, pharmacokinetic analysis showed significantly higher (p ≤ 0.05) AUC, Cmax, and shorter Tmax. The optimized mini-tablet formulation showed 1.5-fold enhancement of the oral bioavailability compared to mini-tablets containing untreated GLC. It could be concluded that the co-adsorption technique successfully enhanced the oral bioavailability of GLC. Furthermore, the produced mini-tablets have a higher oral bioavailability with a lower GLC dose, which could offer economic benefit for industry as well as acceptability for patients

Electronic Absorption Spectra of New y-Keto-dimethine Cyanine Dyes and Apocyanines

New asymmetrical y-keto-dimethine cyanines (2.-f) were prepared through the condensation of phenyl glycosal derivatives (l.-e) with 2-methyl pyridinium (quinolinium)- 2yl salts. Such dyes were converted into the corresponding dyes (3a-g and 4a-d) by cyclocondensation with hydrazines or hydroxylamine hydrochloride under suitable conditions. The new synthesized cyanines were identified by elemental and spectral analyses. The U\u27V-visible absorption spectra of some selected dyes were investigated in pure and mixed solvents as well as in aqueous buffer solutions. Molecular complex formation with ethanol was verified by mixed solvent studies. Electronic transitions were attributed to either locally excited or predominantly charge transfer states. The spectral shifts were discussed in relation to molecular structure and in terms of medium effects. The variation of absorbance with pR was utilized for the determination of the pK. value for aselected compound (2e). The photostability of some selected đyes (2e, 3g and 4d) was investigated

Effect of Tadalafil on Penile Duplex parameters in Erectile Dysfunction Patients

Background: Tadalafil is a PDE-5 (phosphodiesterase inhibitor) inhibitor that supports endogenous nitric oxide's vasodilatory actions and aids in erection maintenance. The penile duplex has proven to be very useful for imaging superficial structures and for determining the reasons of erectile dysfunction (ED). Objectives: To assess the effect of daily oral tadalafil 5mg for 3 months on penile duplex parameters in erectile dysfunction patients. Patients and Methods: A case control study involved 30 Egyptian patients ED. Appropriate clinical history and penile duplex examination before and after treatment with daily oral tadalafil mg for 3 months were performed. Results: The mean age of the patients was 53.17 ± 7.8 years. We founded that there was significant (p < 0.001) improvement in the level of erection after treatment. The rate of erection E1 and E2 was decreased from 53.3% to 3.3%. Likewise, the rate of E3-E5 was increased from 46.7% to 96.7%. Moreover, the mean duration of erection was elongated from 24.7 ± 5.3 to become 37.4 ± 3.8 and this was statistically significant (p < 0.001). Also, the mean peak systolic volume (PSV) was significantly (p = 0.001) increased after treatment (38.4 ± 9.1 cm/s) compared with the pre-treatment levels (23.9 ± 6.1 cm/s). Unlikely, the mean end diastolic volume (EDV) was insignificantly (p = 0.340) lower in post-treatment (2.25 ± 0.5 mL) compared with pre-treatment levels (2.97 ± 0.4 mL). Likely, the mean resistant index (RI) showed insignificant difference (p = 0.965) after treatment (0.9 ± 0.02) compared with before treatment (0.9 ± 0.08). For penile artery diameter, there was significant (p = 0.009) increase in the diameter after treatment (0.9 ± 0.1 mm) compared with before treatment (0.8 ± 0.1 mm). Conclusion: Oral daily tadalafil 5mg for 3 months is considered an effective treatment for ED according to penile duplex parameters