This study focuses on the effects of an adhesive defect and adherend type and material on stress distribution in laminated composite tubular joints sustaining axial tensile loads. The tubular joint comprised two hollow tubes joined by a layer of adhesive to form a simple lap joint, hosting a cylindrical void or debond. The adherends were assumed to be either isotropic, quasi-isotropic, orthotropic, or transversely isotropic. Applying linear elasticity, the equilibrium equations were derived and solved using the differential quadrature method. Furthermore, finite element models of the joint were prepared and solved to support the semi-analytical solutions. Good agreements were observed between the results of both methods. Based on the results, for a defect-free joint with a bond length of 30 mm, nearly 80% of the bond length experienced zero peel stress (σr), while this value was about 20% for the peak interfacial shear stress (τrx)max. Additionally, among the selected types of glass/epoxy outer tubes, the [08] lamination setup minimized (τrx)max while (σr)max was the least for the quasi-isotropic arrangement of [0/90/-45/45]S. Moreover, replacing the aluminum inner tube with steel, reduced the tensile peak peel stress by 38% and increased the peak shear stresses by 12%. However, compared to a defect-free joint, a void/debond in the adhesive layer highly affected the magnitudes and locations of the adhesive peak interfacial shear and the tensile peel stresses. Additional results showed that in a defective adhesive hosting a void, the application of [08] transversely isotropic carbon/epoxy can reduce the adhesive peak shear stresses by 200% compared to glass/epoxy.

In this article, the influence of various vacancy defects on the Young’s modulus of carbon nanotube (CNT) - reinforcement polymer composite in the axial direction is investigated via a structural model in ANSYS software. Their high strength can be affected by the presence of defects in the nanotubes used as reinforcements in practical nanocomposites. Molecular structural mechanics (MSM) /finite element (FE) Multiscale modeling of carbon nanotube/polymer composites with linear elastic polymer matrix is used to study the effect of CNT vacancy defects on the mechanical properties. The nanotube is modeled at the atomistic scale using MSM, whereas the interface we assumed to be bonded by Vander Waals interactions based on the Lennar- Jonze potential at the interface and polymer matrix. A nonlinear spring is used for modeling of interactions. It is studied for zigzag and armchair Nanotubes with various aspect ratios (Length/Diameter). Finally, results of the present structural model show good agreement between our model and the experimental work.

Zebrafish (Danio rerio) early-life stages of larvae were used to investigate behavioral, genetical and neurochemical changes promoted by the aquatic toxicity associated with the widely used medicines including naproxen (NPX) and titanium dioxide (TiO2), individually or in combination. Zebrafish as a biological model system genetically very similar to human. This study was carried out with a control (C) group and six treatments including TiO2 at 2 (2T) and 4 mg/L (T4), 50 µg/L (50N) and 100 µg/L (100N) of NPX, 2 mg/L TiO2+50 µg/L NPX (2T50N) and 4 mg/L TiO2 + and 100 µg/L NPX, (4T100N). Approximately 48 hours post-fertilization (hpf), the groups exposed to 4 mg/L TiO2 individually or in combination of 100 µg/L NPX induced large suites of symptoms in zebrafish (D. rerio) early-life stage, including hatching inhibition particularly in 50 and 100 µg/L exposed groups (10. 0% and 10. 3%, respectively), increased mortality specially in the group 4T100N (39. 6%), high heart-beat, and few morphological abnormalities. At approximately 168 hpf, severing of the yolk sac and pericardium oedema, severe swim bladder inflation, short tail with axial malformation, and small eyes were other significant occurrences in D. rerio exposed particularly to 100 µg/L NPX, which can be collectively referred to as pigeon chest deformity. The results of mRNA expression of neurogenesis-and growth-associated genes of the targeted ones presented that gfap mitigated exception for 2T group compared to the control group. For mbp, fish of all groups showed downward gene expression, except for 100N group exhibited a normal expression compared to the control as well as the situation observed for AChE, although the fish showed relatively downward gene expression compared to the control group. The brain showed apoptosis as vacuoles in 4T and 50N groups. It is concluded that TiO2 had low acute toxicity to the embryos and larvae of D. rerio compared to NPX and could be used in different industries with low-risk rate, while it was used at low concentration (2 mg/L or less). although exposure to higher concentrations (4 mg/L or more) resulted in the increase of susceptibility risk of diseases.

Chromosomal defects are one of the commonest congenital defects responsible for fetal and neonatal death and handicap. The traditional method of screening for Down’s syndrome has been maternal age where amniocentesis or chorionic villous sampling is offered to women aged 35 years or more. This results in the need for an invasive test in 15-20% of pregnant women with a detection of less than half of the fetuses with Down’s syndrome, because the majority of affected fetuses come from the younger age group. A more effective method of screening is based in the combination of: maternal age, a maternal blood sample for the measurement of the placental products of free b-hCG and PAPP-A and an ultrasound scan at 11-13 weeks; to measure the collection of fluid behind the fetal neck (nuchal translucency), to examine the fetal nose and palate, to measure the fetal heart rate and to assess the flow of blood across the tricuspid valve of the fetal heart and the ductus venosus.This new method of screening reduces dramatically the number of women requiring an invasive test from about 20% to less than 3% and at the same time increases the detection rate of Down’s syndrome and other major chromosomal abnormalities from less than 50% to more than 95%.There are several other benefits of the 11–13 weeks scan as well including: accurate dating of the pregnancy, early diagnosis of many major fetal abnormalities, and the detection of multiple pregnancies with reliable diagnosis of chorionicity, which is the main determinant of the outcome in multiple pregnancies Although there are some markers at second trimester (sonographic and biochemical) to assess risk of chromosomal abnormalities but detection rate is less than first trimester and also early diagnosis ( in first trimester) and early termination is much better regarding patient’s preferences, less complications and less psychological stress.

Axial slot CTs were designed and applied on Rotor 67 to understand the physical mechanisms responsible for the improvement of the stall margin. Unsteady Reynolds-averaged Navier-Stokes was applied in addition to steady Reynolds-averaged Navier-Stokes to simulate the flow field of the rotor. The results show that aerodynamic performance and the rotor stability were improved. Stall margin improvement (SMI) improved by 26. 85% after the CT covering 50% of the axial tip chord was applied, whereas peak efficiency (PE) decreased the least. The main reason for the rotor stall in the solid casing is the blockage caused by tip leakage flow. After axial slot CTs were applied, the tip leakage flow in the front part of the chord was obviously reduced, and the majority of the blockages in the tip region were removed. The absolute value of the axial momentum before 45% axial chord in CT_50 was reduced by 50%, whereas the maximum tangential momentum value of CT_50 was decreased by 70% relative to the solid casing. CT_50 configuration was located across the shock wave; thus, it can fully utilize the pressure gradient to bleed and remove the blockage region, and the across flow is considerably depressed.