Analysis of Solid State Bonding in the Extrusion Process of Magnesium Alloys -Numerical Prediction and Experimental Verification

The automotive industry developments focused on increasing fuel efficiency are accomplished by weight reduction of vehicles, which consequently results in less negative environmental impact. Usage of low density materials such as Magnesium alloys is an approach to replace heavier structural components. One of the challenges in deformation processing of Magnesium is its low formability attributed to the hexagonal close packed (hcp) crystal structure. The extrusion process is one of the most promising forming processes for Magnesium because it applies a hydrostatic compression state of stress during deformation resulting in improved workability. Many researchers have attempted to fully understand solid state bonding during deformation in different structural materials such as Aluminum, Copper and other metals and alloys. There is a lack of sufficient understanding of the extrusion welding in these materials as well as very limited knowledge on this subject for hollow profiles made from Magnesium alloys. The weld integrity and the characteristic of the welding microstructure are generally unknown. In this dissertation three related research projects are investigated by using different tools such as microstructure characterization, mechanical testing, thermo-mechanical physical simulation and finite element numerical modeling. Project 1: Microstructure characterization supported by mechanical testing of the extrusion welding regions in Magnesium alloy AM30 extrudate. The microstructure characterization was conducted using Light Optical Microscopy (LOM), in addition to LOM the electron backscattered diffraction (EBSD) technique was implemented to characterize in depth the deformed and welded microstructure. Project 2: Finite element numerical simulation of AM30 extrudate to model different process parameters and their influence on localized state variables such as strain, strain rate, temperature and normal pressure within the weld zone. Project 3: Physical simulation of the extrusion welding by using Gleeble 3500 thermo-mechanical simulator to create deformation welds in Magnesium alloy AM30 samples in compression test under various temperatures and strain rates conditions.Based on the obtained results from the performed research projects and literature review, a new qualitative criterion of extrusion welding has been introduced as contribution to the field. The criterion and its analysis have provided better understanding of material response to processing parameters and assisted in selecting the processing windows for good practices in the extrusion process. In addition, the new approach contributed to better understanding and evaluating the quality of the solid state bonding of Mg alloy. Accordingly, the criteria help to avoiding formation of potential mechanical and metallurgical imperfections

Intestinal, Airway, and Cardiovascular Relaxant Activities of Thymoquinone

Thymoquinone (TQ) is a bioactive component found in many medicinal herbs. In this study, we report the smooth and cardiac muscle relaxant activities of this compound. TQ concentration dependently suppressed spontaneously contracting rabbit jejunum while also relaxed high K+-(80 mM) induced contractions in jejunum and guinea-pig ileum, indicating activity at voltage-operated Ca++ channels (VOCC). Further, TQ displaced Ca++ concentration-response curves, obtained in a Ca++-free environment, to the right, showing blockade of VOCC. Similar activity was observed with verapamil, a standard VOCC blocker. TQ also exhibited nonadrenergic relaxation of agonist-induced contractions in guinea-pig trachea. When tested in fluo-4-loaded mouse lung slices, TQ inhibited ACh-induced airway narrowing and Ca++ signalling in airway smooth muscle cells. In endothelium-intact and endothelium-denuded rat aorta, TQ inhibited high K+-induced contractions at significantly lower concentrations than phenylephrine-(PE-) (1 microM) induced contractions. Relaxation of PE-induced contractions was resistant to blockade by L-NAME and atropine. In guinea-pig atria, TQ showed noncholinergic relaxation of atrial force and rate of contractions. These data suggest smooth and cardiac muscle relaxant activity of TQ possibly mediated, in part, via blockade of VOCC. The results also justify the use of TQ containing plants in related health disorders like colic, diarrhoea, cough, and asthma

Extremely low profile flexible antenna for medical body area networks

Medical Body Area Networks (MBAN) are widely used in healthcare systems employing in- and on-body applications. An extremely low profile patch antenna for the MBANs is presented in this paper. The antenna consists of two flexible printed circuit boards (FPCB) separated by an air gap and uses a rectangular radiating patch with four slots. Two variants of the antenna having single and dual band operation are discussed. The single band antenna operates at 2.4 GHz while the dual band antenna works at frequencies of 2.4 GHz and 4.3 GHz. Both versions of the proposed antenna offer good bandwidth, high gain and radiation coverage for the MBAN applications

Nanoparticulate Iron Oxide Minerals for Arsenic Removal from Contaminated Water

Groundwater contamination with arsenic (As) is a global environmental and human health problem affecting over 200 million people worldwide, with low to high concentrations of As via drinking well water. Therefore, remediation of As-contaminated water has been under discussion over the last 3 to 4 decades given its highly toxic and carcinogenic properties of As compounds, particularly inorganic arsenite and arsenate species. Several types of sorption techniques have been used to remove As from water such as clay minerals, biochars, metal oxides (e.g., iron oxide minerals), microbes and algae. This chapter provides: (1) insights on the significance of nanoparticulate iron (Fe) oxide minerals (such as nano-ferrihydrite, nano-goethite, nano-magnetite) for their efficiency in the removal of As from contaminated water; (2) develops critical understanding for several As removal methods, compares their potential for As remediation, and critically examines the properties and effectiveness of nanoparticulate Fe oxide minerals to remove As in drinking water or wastewater; and (3) implication of the nanotechnology in remediation of As-rich water. This chapter also elucidated the mechanism of As removal using Fe-oxide nanoparticles in detail

A Low Profile Antenna for Millimeter-Wave Body-Centric Applications

Millimeter-Wave (mm-Wave) frequencies are a front runner contender for the next generation body-centric wireless communications. In this paper, the design of a very low-profile antenna is presented for body-centric applications operating in the mm-Wave frequency band centered at 60 GHz. The antenna has an overall size of 14 × 10.5 × 1.15 mm 3 and is printed on a flexible printed circuit board. The performance of the antenna is evaluated in off-body, on-body, and bodyto-body communication scenarios using a realistic numerical phantom and verified through measurements. The antenna has a bandwidth of 9.8 GHz and offers a gain of 10.6 dBi in off-body (free space) configuration, while 12.1 dBi in on-body configuration. It also achieves an efficiency of 74% in off-body and 63% in on-body scenario. The small and flexible structure of the antenna along with excellent impedance matching, broad bandwidth, high gain, and good efficiency makes it a suitable candidate to attain simultaneous data transmission/reception at mm-Wave frequencies for the 5G body-centric applications

Effects of bomb blast injury on the ears: The Aga Khan University Hospital experience

Abstract Objective: To evaluate the frequency and effects of blast-related otologic injuries. Methods: This retrospective study was conducted at the Aga Khan University Hospital, Karachi, and comprised charts of patients who were victims of bomb explosions between January 2011 and July 2013. Frequency and percentages were reported using cross tabulation with size of bomb, distance of person from blast and the presence of victim in open or closed space. Association of associated variables were also analysed. Results: Of the 100 patients, 81(81%) were men and 19(19%) were women. Besides, 68(68%) patients were aged \u3c30 years. Also, 78(78%) subjects were exposed to \u3c 80kg of explosives and 68(68%) were at a distance of\u3e10m. Furthermore, 61(61%) patients were exposed to explosion in openspace. The prevalence of ear injuries was 21(21%). The odds of experiencing various symptoms of ears was high in those who were exposed to \u3e80 kg of explosives (odds ratio: 3.38; 95% confidence interval, 1.16, 9.91). The odds of hearing loss in those who were within 10m was 8.62 (95% confidence interval: 2.72, 27.28) times than those who were \u3e10 m from the site of explosion. Conclusion: Otologic injuries were frequently associated with large blasts

Preparation, characterization and therapeutic properties of gum Arabic-stabilized gallic acid nanoparticles

Gallic acid (GA) is a natural phenolic compound with therapeutic effects that are often challenged by its rapid metabolism and clearance. Therefore, GA was encapsulated using gum arabic into nanoparticles to increase its bioavailability. The formulated nanoparticles (GANPs) were characterized for physicochemical properties and size and were then evaluated for antioxidant and antihypertensive effects using various established in vitro assays, including 1,1-diphenyl-2-picrylhydrazyl (DPPH), nitric oxide scavenging (NO), β-carotene bleaching and angiotensin-converting enzyme (ACE) inhibitory assays. The GANPs were further evaluated for the in vitro cytotoxicity, cell uptake and cell migration in four types of human cancer cell lines including (MCF-7, MDA-MB231) breast adenocarcinoma, HepG2 hepatocellular cancer, HT-29 colorectal adenocarcinoma, and MCF-10A breast epithelial cell lines. The GANPs demonstrated potent antioxidant effects and have shown promising anti-cancer properties in a dose-dependent manner with a predilection toward HepG2 and MCF7 cancer cells. The uptake of GANPs was successful in the majority of cancer cells with a propensity to accumulate in the nuclear region of the cells. The HepG2 and MCF7 cancer cells also had a significantly higher percentage of apoptosis and were more sensitive to gallic acid nanoparticle treatment in the cell migration assay. This study is the first to confirm the synergistic effects of gum Arabic in the encapsulation of gallic acid by increasing the selectivity towards cancer cells and enhancing the antioxidant properties. The formulated nanoparticles also had remarkably low toxicity in normal cells. Based on these findings, GANPs may have promising therapeutic applications towards the development of more effective treatments with a probable targeting precision in cancer cells