Entrained defects and mechanical properties of aluminium castings

The presence of entrained double oxide films, known as bifilms, has been identified as a contributing factor to the variability in mechanical properties observed in aluminium castings. These bifilms consist of folded-over oxide films containing gas-filled crevices and are formed due to turbulence on the liquid metal's surface during handling and pouring. Additionally, it has been suggested that hydrogen dissolved in the aluminium melt can permeate these defects, causing them to expand and leading to the formation of hydrogen porosity. This, in turn, exacerbates the detrimental effects on the mechanical properties of the castings. In this study, the ultimate tensile strength (UTS) and percentage elongation of sand cast bars were compared under various casting conditions. These parameters were chosen as indicators of casting reliability, which was expected to be influenced by the presence of oxide films. The results indicated that incorporating filters in the gating system and reducing the runner height led to a noticeable improvement in tensile strength and elongation. This improvement was attributed to enhanced mold filling conditions, which reduced the likelihood of oxide film entrainment. The findings of this research provide valuable insights into the factors that affect the properties of light metal alloy castings. By understanding these influences, it becomes possible to develop improved practices that result in healthier castings with enhanced mechanical properties

Influence of bifilm defects generated during mould filling on the tensile properties of Al–Si–Mg cast alloys

Entrapped double oxide film defects are known to be the most detrimental defects during the casting of aluminium alloys. In addition, hydrogen dissolved in the aluminium melt was suggested to pass into the defects to expand them and cause hydrogen porosity. In this work, the effect of two important casting parameters (the filtration and hydrogen content) on the properties of Al–7 Si–0.3 Mg alloy castings was studied using a full factorial design of experiments approach. Casting properties such as the Weibull modulus and position parameter of the elongation and the tensile strength were considered as response parameters. The results suggested that adopting 10 PPI filters in the gating system resulted in a considerable boost of the Weibull moduli of the tensile strength and elongation due to the enhanced mould filling conditions that minimised the possibility of oxide film entrainment. In addition, the results showed that reducing the hydrogen content in the castings samples from 0.257 to 0.132 cm3/100 g Al was associated with a noticeable decrease in the size of bifilm defects with a corresponding improvement in the mechanical properties. Such significant effect of the process parameters studied on the casting properties suggests that the more careful and quiescent mould filling practice and the lower the hydrogen level of the casting, the higher the quality and reliability of the castings produced

Effect of runner thickness and hydrogen content on the mechanical properties of A356 alloy castings

Earlier studies demonstrated the detrimental effect of entrained bifilm defects on aluminum cast alloys’ tensile and fatigue properties. It was suggested that hydrogen has a contributing role as it diffuses into the bifilms and swells them out to form hydrogen porosity. In this study, the effect of the runner height and hydrogen content on the properties of A356 alloy castings was investigated using a two-level full factorial design of experiments. Four responses, the Weibull modulus and position parameter of both the ultimate tensile strength (UTS) and % elongation, were assessed. The results suggested that decreasing the runner height and adopting procedures intended to decrease the hydrogen content of the casting caused a considerable enhancement of the Weibull moduli and position parameters of the UTS and % elongation. This was reasoned to the more quiescent practice during mold filling, eliminating the possibility of bifilm formation as well as the decreased hydrogen level that eliminated the amount of hydrogen diffused into the bifilms and accordingly decreased the size of the entrained defects. This, in turn, would allow the production of A356 cast alloys with better and more reproducible properties

Prognostic significance of COX-2 and b-catenin in colorectal carcinoma

Background: The high prevalence of colorectal carcinoma (CRC) is a driver to understand the underlying molecular mechanisms. Chemoprevention strategy using non-steroidal antiinflammatory drugs (NSAIDs) revealed that these drugs suppress colorectal carcinoma. The best known targets of NSAIDs are cyclooxygenase (COX) enzymes. The function of prostaglandins and cyclooxygenase in cancer pathogenesis is unclear. COX-2 regulation of proliferation, apoptosis, and tumor-blood vessel interaction has been suggested. b-Catenin is a component of the WNT (wingless type) signaling pathway, increased protein concentrations promote transcription of genes important in regulating the cell cycle.Aim: To determine the significance of COX-2 and b-catenin expression in colorectal carcinogenesis and prognosis.Patients and methods: Thirty patients with colorectal carcinomas treated by colonic resection were studied for the expression of both COX-2 and b-catenin by immunohistochemistry. Their expression was interpreted in relation to adjacent normal colonic mucosa and analyzed in correlation with various clinicopathologic parameters and patient’s survival after a follow up period of 24 months.Results: Our results showed that in normal adjacent colonic mucosa, COX-2 was completely absent, whereas b-catenin was specifically located in the plasma membranes. Both proteins were expressed in tumorous tissues, COX-2 showed diffuse cytoplasmic positivity, whereas b-catenin accumulated in both the cytoplasm and nuclei. We established statistically significant relationships between pathological grade and both b-catenin, and COX-2 positivity scores, being at the higher end for poorly-differentiated tumors. b-Catenin expression also correlated significantly with higher tumor stage and LN metastasis. Both COX-2 and b-catenin expression correlated with a higher incidence of shorter disease free survival.Conclusion: Both b-catenin and COX-2 expression may play an important role in the evolution of colon carcinogenesis. Increased expression of both could be used as a marker of tumor progression and poor prognosis. This might be of therapeutic value for allocating patients with colorectal carcinoma to different treatment modalities.Keywords: b-Catenin COX-2 Colorectal carcinoma Immunohistochemistry Prognosi

Design optimisation of additively manufactured titanium lattice structures for biomedical implants

A key advantage of additive manufacturing (AM) is that it allows the fabrication of lattice structures for customised biomedical implants with high performance. This paper presents the use of statistical approaches in design optimisation of additively manufactured titanium lattice structures for biomedical implants. Design of experiments using response surface and analysis of variance were carried out to study the effect design parameters on the properties of the AM lattice structures such as ultimate compression strength, specific compressive strength, elastic modulus, and porosity. In addition, the lattice dimensions were optimized to fabricate a diamond cellular structure with properties that match human bones. The study found that the length of a diamond-shaped unit cell strut is the most significant design parameter. In particular, the porosity of the unit cell increases as the strut length increases, while it had a significant reverse effect on the specific compressive strength, elastic modulus and ultimate compression strength. On the other hands, increasing the orientation angle was found to reduce both the specific compressive strength and modulus of elasticity of the lattice structure. An optimised lattice structure with strut diameter of 0.84 mm, length of 3.29 mm and orientation angle of 47° was shown to have specific compressive strength, elastic modulus, ultimate compression strength and porosity of 37.8 kN.m/kg, 1 GPa, 49.5 MPa and 85.7%, respectively. A cellular structure with the obtained properties could be effectively applied for trabecular bones replacement surgeries

Optical signatures of intrinsic electron localization in amorphous SiO2

We measure and analyse the optical absorption spectra of three silica glass samples irradiated with 1 MeV electrons at 80 K, where self-trapped holes are stable, and use ab initio calculations to demonstrate that these spectra contain a signature of intrinsic electron traps created as counterparts to the holes. In particular, we argue that optical absorption bands peaking at 3.7, 4.7, and 6.4 eV belong to strongly localised electrons trapped at precursor sites in amorphous structure characterized by strained Si–O bonds and O–Si–O angles greater than 132°. These results are important for our understanding of the properties of silica glass and other silicates as well as the reliability of electronic and optical devices and for luminescence dating

ABO BLOOD GROUPS IN CORRELATION WITH HYPERLIPIDEMIA, DIABETES MELLITUS TYPE II AND ESSENTIAL HYPERTENSION

Objectives: There are associations between ABO blood groups and systemic diseases. So we aim to explore any associations among ABO blood groupwith hyperlipidemia; diabetes mellitus (DM) type II, and essential hypertension.Methods: A total of 800 subjects were recruited. Patients groups were subdivided into hyperlipidemia group (n=100), DM type II group (n=160),and hypertension group (n=166). Fasting blood sample was collected and plasma samples used for measuring of 2, 3-dinor-6-keto-prostaglandinF1α (PGF1α), 11-dehydro-thromboxane (TX) B2, insulin, triglycerides (TGs), total cholesterol (Tc), high-density lipoprotein cholesterol (HDL-C),prothrombin time (PT), activated partial PT (aPPT), blood group type, random blood glucose level, and body mass index (BMI) were also determined.Results: Blood Group A demonstrates a significant elevation in insulin, random blood sugar (RBS), Tc, TGs, and low-density lipoprotein (LDL)/HDLratio and shows a significant decrease in prostacyclin. Blood group B demonstrates a significant elevation in TXB, Tc, TGs, and LDL/HDL ratio andshows a significant decrease in PT. Blood group AB demonstrates a significant elevation in PT, and prostacyclin and shows a significant decrease ininsulin, RBS, Tc, TGs, and LDL/HDL. Blood group O demonstrates a significant elevation in PT, and prostacyclin and shows a significant decrease inTXB2, Tc, TGs, and LDL/HDL ratio.2Conclusions: Blood group AB is protective against hyperlipidemia, diabetes, thrombosis, and hypertension, blood group O is protective againstcardiovascular diseases while blood group B followed by A are risk factors for hypertension and blood group A is a risk factor for diabetes. Thesefindings are establishing the ethnic-dependent correlation of ABO groups and studied diseases.Keywords: Hyperlipidemia, DM type II, Hypertension, Thrombosis, ABO blood groups

Shear Behavior of Steel I-Beams Strengthened With CFRP Strips

This paper studies the behavior of simply supported steel I-beams strengthened with carbon fiber reinforced polymers (CFRP) strips on the web as shear reinforcement. The experimental program contains seven simply supported steel beams. One of them was considered as a control beam and the other specimens were strengthened with different schemes; varying the position of CFRP strips to the web, its number of layers and its angle of orientation. The results show that applying CFRP strips on the web of the steel I-beams was an effective strengthening method for increasing the load bearing capacity and decreasing the deformations. Using two layers of diagonal CFRP strips on both sides of the web realized the highest increasing in the load capacity. Moreover, finite element analysis method has been utilized to analyze the tested specimens using ANSYS. A great convergence between the experimental results and the corresponding ones obtained from finite element simulation

Simulation: Early Detection of Brain Vessels Stroke by Applying Electromagnetic Waves Non-Invasively

Introduction: Early recognition of stroke with its two types Ischemic and Hemorrhagic, is one of the most crucial research points, commonly used methods are CT- (computerized tomography), and MRI- (Magnetic resonance imaging). These techniques cause a delay in the detection of the condition, which causes permanent disability. The main reason behind the fatal consequences of stroke is the delay of detection. Therefore, this research paper aims to early detection of the type of stroke without delay until the appropriate diagnosis of each type is made, and then the appropriate treatment without delay. Method: Using a non-invasive and fast technique to determine the stroke type by wave, we simulate and design a vessel containing a liquid as a laminar flow with the same density and velocity of blood, and it was surrounded by a Homogenized multi-turn coil consisting of (n) turns to represent the magnetic field, using specific frequency (HZ) with Electrical field in coil current (A) to see the changing in magnetic flux density (MFD), Depending on the changes in MFD, the flow of blood in laminar flow can be affected by clotting (Ischemic) or Hemorrhagic (cutting) in our vessel designed. We have built three different scenarios to apply the technique which are: First: Normal Scenario (where the blood in vessel has no problem), second: clotting (ischemic, where the vessel blocked in specific three position) and Third: Cutting (Hemorrhagic, where the vessel cut in certain nine positions). Results: This paper presents-through our own design-the studying of applying the electromagnetic waves on blood inside the vessel to detect the stroke type in our three scenarios (normal, ischemic three positions or hemorrhagic nine positions), Studying the magnetic field and laminar flow. This study covered in three areas. First: coil geometry analysis, Second: stationary, and Third: frequency domain. through the changes in Magnetic Flux Density -MFD- waves. The results were promising and distinct for distinguishing between the three scenarios which are normal, ischemic (3 positions) and hemorrhagic (9 positions) the results of MFD are: 0.09 to 3.3*10^-3, 0.08 to 3.15*10^-4, 0.15 to 6.2*10^-3 respectively