Void nucleation and growth from heterophases and the exploitation of new toughening mechanisms in metals

Heterophases, such as precipitates, inclusions, second phases, or reinforcement particles, often drive void nucleation due to local incompatibilities in stresses/strains. This results in a significant life-limiting condition, as voids or their coalescence can lead to microcracks that reduce the ductility and fatigue life of engineering components. Continuum-mechanics-based analytical models have historically gained momentum due to their relative ease in predicting failure strain. The momentum of such treatment has far outpaced the development of theories at the atomic and micron scales, resulting in an insufficient understanding of the physical processes of void nucleation and growth. Evidence from the recent developments in void growth theories indicates that the evolution of voids is intrinsically linked to dislocation activity at the void–matrix interface. This physical growth mechanism opens up a new methodology for improving mechanical properties using hydrostatic pressurization. According to the limited literature, with a hydrostatic pressure close to 1 GPa, aluminium matrix composites can be made 70 times more ductile. This significant ductility enhancement arises from the formation of dislocation shells that encapsulate the heterophases and inhibit the void growth and coalescence. With further investigations into the underlying theories and developments of methods for industrial implementations, hydrostatic pressurization has the potential to evolve into an effective new method for improving the ductility and fatigue life of engineering components with further development

In vitro synergistic cytoreductive effects of zoledronic acid and radiation on breast cancer cells

INTRODUCTION: Bisphosphonates are mostly used in the treatment of bone metastases. They have been shown to act synergistically with other chemotherapeutic agents. It is not known, however, whether similar synergistic effects exist with radiation on breast cancer cells. METHODS: Human MCF-7 breast cancer cells were treated with up to 100 μM zoledronic acid, were irradiated with up to 800 cGy or were exposed to combinations of both treatments to determine the antiproliferative effects of zoledronic acid and radiation. RESULTS: Zoledronic acid and radiation caused a dose-dependent and time-dependent decrease in cell viability (approximate 50% growth inhibition values were 48 μM and 20 μM for 24 hours and 72 hours, respectively, for zoledronic acid and 500 cGy for radiation). A synergistic cytotoxic effect of the combination of zoledronic acid and radiation was confirmed by isobologram analysis. CONCLUSION: These data constitute the first in vitro evidence for synergistic effects between zoledronic acid and radiation. This combination therapy might thus be expected to be more effective than either treatment alone in patients with metastatic breast carcinoma

Evaluation of Oral Mucosal Lesions in 598 Referred Iranian Patients

The mucosal membrane of the oral cavity displays at times classical developmental lesions considered to be variations of normal structures rather than having disease characteristics. Of these lesions leukoedema, Fordyce granules, geographic-, fissured- and hairy tongue, median rhomboid glossitis and lingual varices were studied in 598 patients referred to the School of Dentistry, Tehran, Iran. The prevalence was studied in relation to age, gender, occupation, education, smoking habits, general health, addictions and or drug therapies. Oral developmental lesions were seen in 295 patients (49.3%). Only Fordyce granules (27,9%), fissured tongue (12,9%), leukoedema (12,5%) and hairy tongue (8,9%) had enough cases for statistical analysis. Three of these lesions increased with age but not fissured tongue. All were more common in men. After adjusting for age, the parameters education, occupation and complaints upon referral had little influence on the prevalence of the lesions. Fewer Fordyce granules were seen in oral mucosa of smoking men. Leukoedema and hairy tongue were significantly associated with smoking, leukoedema with diabetes mellitus. We conclude that there was a highly significant association between these oral lesions and age, gender and smoking. Few significant associations were found between oral lesions and general diseases

Electrophoretic co-deposition of PEEK-hydroxyapatite composite coatings for biomedical applications

PMID = 2977247

Electrochemical Impedance of Sn Nanowire Arrays

In this study, Sn nanowires were produced electrochemically in anodic aluminum oxide membranes. During the deposition process some parameters such as ion content, pH, deposition time, and temperature of solution were kept constant. The scanning electron microscope results showed that the diameters of produced tin nanowires were approximately 300 nm and their lengths were about 8-10 μm. Electrochemical impedance studies of Sn nanowire arrays were also studied by Iviumstat galvanostat/potentiostat system

Optimization of Surface Properties of Shot Peened TI6AL4V Alloy

As an important surface treatment method, shot peening (SP) is widely used in automotive and aerospace industries in order to improve surface properties. In the present study SP was performed on the α-β titanium alloy Ti6Al4V under various parameters (particle impingement angle, particle acceleration pressure and particle size) by using a specially designed shot peening test rig. It is aimed to optimize surface roughness and hardness of the shot peened Ti6Al4V alloy under various parameters. In order to achieve this goal shot peened samples were investigated in detail by using a non-contact laser optical profilometer and surface hardness of the samples was measured by using a micro-hardness instrument. The surface roughness values, 3D surface morphologies and micro-hardness of the samples were obtained and examined. The results show that particle impingement angle, particle acceleration pressure and particle size dramatically affect the surface properties of the Ti6Al4V alloy

Investigation of the Effects of Erosion Test Parameters on the Particle Impengement Velocity by Using CFD Analysis

Particle impingement velocity is one of the most important parameters in solid particle erosion. Particle impingement velocity depends on erosion test parameters such as particle acceleration pressure, erodent particle size and standoff distance. Over the past decades many experimental studies have been conducted to examine the effects of these parameters on the particle impingement velocity. In this study, the effects of particle acceleration pressure, erodent particle size and standoff distance on the particle impingement velocity have been investigated by using a computational fluid dynamics (CFD) program, FLUENT. In order to achieve these goals solid particle erosion tests are simulated under various test parameters and the effects of these parameters are examined in detail. The effect of particle velocity on the flow field is characterized with method geometrics. Two-dimensional plane symmetrical models are utilized to reduce the computation time. Plots of gas pressure and particle velocity contours at the XY symmetrical plane from nozzle inlet to substrate were given. CFD analysis showed that all erosion test parameters have dramatically affected particle impingement velocity. Particle impingement velocity was increased with increases in acceleration pressure while it was decreased with increases in both erodent particle size and standoff distance

Electrophoretic deposition of chitosan-based composite coatings for biomedical applications:A review

Chitosan is one of the most widely used natural biopolymers for a great variety of biomedical applications owing to its biocompatibility, biodegradability, and antibacterial activity, being generally regarded as a safe material. It can be employed as a dispersant, binder, and surface charge agent for particles in suspension. Electrophoretic deposition (EPD) of chitosan, especially in combination with other materials, is receiving increasing attention for biomedical applications. This article presents a comprehensive review of the field of EPD of chitosan-based composite coatings by highlighting their microstructural, mechanical, surface, and biological properties. Since suspension characteristics have significant influences on the deposition mechanisms, kinetics, and on the overall properties of the electrophoretically deposited coatings, suspension parameters such as concentration, viscosity, and zeta potential are discussed, including chitosanbased suspensions with hydroxyapatite, bioactive glass particles, carbonaceous materials and other inorganic and organic materials. The deposition mechanisms proposed for each composite system are highlighted. Moreover, the effects of key EPD process parameters on the micro structural homogeneity, mechanical properties as well as surface and biological characteristics of the coatings are emphasised, and specific approaches for future research are proposed based on the state-of-the-art and considering EPD produced chitosan-based coatings in applications such as tissue engineering and drug delivery systems