Preparation of superhydrophobic and self-cleaning polysulfone non-wovens by electrospinning: influence of process parameters on morphology and hydrophobicity

Electrospinning is used to prepare hydrophobic and self-cleaning polysulfone (PSf) surfaces. The effects of PSf concentration in Dimethylformamide (DMF) solvent and electrospinning process parameters on the surface structure and hydrophobicity are investigated. The experimental results show that depending on PSf concentration, three types of morphologies are obtained: beads, beads-on-strings, and free-beads fibers. The surface hydrophobicity depends mainly on the resultant surface morphology, and the existence of beads increases hydrophobicity. The contact angle (CA) is found to increase from 73° for smooth PSf surface to more than 160° for surfaces formed by electrospinning. Moreover, the contact angle hysteresis (CAH) was generally less than 10° for all the chemistries. It is noted that increasing the PSf concentration leads to the formation of beads-on-string and free-beads fiber structures; this morphological change is accompanied by a reduction in the contact angle. Surface structures are found to be more sensitive to electrospinning feed rate than to electrospinning voltage; however, these two parameters have a negligible influence on the hydrophobicity. Porosity measurements of different chemistries show an average pore size in the range 3–8 microns. The thickness of PSf mats was variable, from as low as 10 μm to as high as 70 μm.King Fahd University of Petroleum and Minerals (KFUPM-MIT Project No. R16-DMN-11)King Abdulaziz City of Science and Technology (Saudia Arabia) (Project No. 11-ADV2134- 04

Hypoglycemic and antihyperglycemic effects of Anabasis articulata (Forssk) Moq (Chenopodiaceae), an Algerian medicinal plant

Anabasis articulata leaves decoction is widely used by Algerian traditional medicine practitioners as a remedy for the treatment of diabetes. The aqueous extract was found to be non-toxic at 1000 mg/kg, asno deaths or hazardous signs were recorded during treatment or the observation period (24 and 72 h) in either control or treated groups of mice. Experiments were performed in non-diabetic mice, and inhyperglycemic mice (glucose treated and alloxan treated mice) to confirm the antidiabetic potential of A. articulata. Our results showed that the orally administration at a dose of 400 mg/kg decreased the glycaemia by 29.89% after 6 h (p < 0.05), corresponding to the greatest decrease of blood glucose in normoglycaemic mice. This dose also lowered blood glucose concentrations in diabetic mice revealing antihyperglycemic effect of A. articulata leaves. The class of phytochemical responsible for antidiabetic effects in aqueous leaf extract was also investigated. Phytochemical screening showed that the aqueous extract contains alkaloids (1.25%) and saponin (1.30%). Our findings showed that saponin (5 mg/Kg) was the active fraction, since it restores the normal blood glucose levels after 21 days of treatment. The alkaloid fraction did not significantly reduce the blood glucose level. The present studyconfirms the antidiabetic proprieties of A. articulata leaves previously reported by Algerian healers

FINITE ELEMENT INVESTIGATION OF INITIAL CLEARANCE EFFECT ON TUBE-TO-TUBESHEET JOINT STRENGTH

The tube-to-tubesheet joint strength is measured in terms of residual contact pressure between the tube’s outer surface and tubesheet hole surfaces. The joint integrity is affected by several design parameters, including the type of material and the initial radial clearance. To avoid weakening of joints due to excessive initial radial clearances Tubular Exchanger Manufacturer Association (TEMA) has set standards in which maximum over-tolerances are spelled out. The present work complements the experimental program on the effect of over-tolerance on heat exchangers tube-to-tubesheet joint strength. The finite element analysis first addressed the ligament effect on the residual stress in order to select a satisfactory sleeve diameter. Second, the initial clearance effect on contact pressure and percent tube wall reduction is performed. Results show that for low strain hardening materials the initial clearance effect is negligible. However, higher levels of strain hardening have a significant effect on residual stress and percent wall reduction. For low clearances, the finite element estimated residual contact pressure compared well with the analytical result and that inferred from the experimentally measured pull-out force. The variation of the percent wall reduction with initial clearance is found to be similar to that of the measured one

FATIGUE DAMAGE IN WOVEN CARBON FABRIC/EPOXY LAMINATES AT NON-AMBIENT TEMPERATURES

The mechanisms involved in initiation and development of non-ambient temperature fatigue damage in Plain Weave-Woven Carbon fabric/epoxy Composite laminates is explored. Laminates obtained from prepreg woven carbon fabric layers were subjected to tension-tension cyclic loading at –20oC, 0oC, 24oC 100oC and 150oC. Two different stacking sequences, a unidirectional [0]8, and an angle plied [0,0,45,-45]s sequence were studied. Optical microscopy, enhanced-dye penetrant X-ray radiography, and scanning electron fractography were employed to examine the fatigue damage mechanisms operative at various temperatures. Temperature was found to have a significant effect on the fiber/matrix bonding and interply delamination characteristics of these woven carbon fabric/epoxy laminates

A Global Collaborative Effort to Enhance Design in a Mechanical Engineering Curriculum in Saudi Arabia

In 2008, King Fahd University of Petroleum and Minerals (KFUPM) in Saudi Arabia and the Massachusetts Institute of Technology (MIT) partnered together to develop project-based curricular material to be tested out in a new undergraduate course offering in KFUPM’s Department of Mechanical Engineering. This paper details some of the unique challenges to collaborating across countries and time zones, and the approaches the KFUPM-MIT team used to address these. These approaches have so far included the establishment of a shared vision for the project and the use of an array of technologies to facilitate distance communication. The paper concludes with a description of lessons learned that might be useful for future programs that plan to engage in international collaboration on design education.Jāmiʻat al-Malik Fahd lil-Batrūl wa-al-Maʻādi

What can crop stable isotopes ever do for us? An experimental perspective on using crop carbon stable isotope values for reconstructing water availability in semi-arid and arid environments

This study re-assesses and refines the use of crop carbon stable isotopes (Δ13C) to reconstruct past water availability. Durum wheat, six-row barley, and sorghum were experimentally grown at three crop growing stations in Jordan for up to three years under five different irrigation regimes: 0% (rainfall only), 40%, 80%, 100%, and 120% of the crops’ optimum water requirements. Results show large variation in carbon stable isotopes for crops that received similar amounts of water, either as absolute water input or as percentage of crop requirements. We conclude that C3 crop carbon stable isotope composition can therefore be best interpreted in terms of extremely high values showing an abundance of water versus low values indicating water-stress. Values in between these extremes are problematic and best interpreted in conjunction with other proxies. C4 crop isotopes were not found to be useful for the reconstruction of water availability