Fatigue Failure from Inner Surfaces of Additive Manufactured Ti-6Al-4V Components

Selective laser melting (SLM) is an additive manufacturing process for producing metallic components with complex geometries. A drawback of this process is the process-inherent poor surface finish, which is highly detrimental in materials submitted to fatigue loading situations. The goal of this work is to analyze the fatigue behavior of Ti-6Al-4V specimens with internal axial channels under the following different conditions: hole drilled, hole as manufactured, and hole threaded M4 × 0.7. All the cases studied showed a lower fatigue performance as compared with solid samples due to the surface roughness and geometry effect that produced a surface stress concentration leading to a reduction in fatigue strength. The fractography revealed that crack initiation occurred from the internal surface in all specimens with internal channel mostly from defects as unfused particles and lack of fusion zones, while for the solid specimens crack initiation was observed from the external surface due to insufficient fusion defect. The application of the Smith-Watson-Topper energy-based parameter was revealed to be a good tool for fatigue life prediction of the different series studied.

X-ray Micro Tomography Study of Internal Defects of Electron Beam Melted Ti6Al4V and Their Effect on Fatigue Behavior

In this work, the fatigue behaviour of Ti6Al4V manufactured using electron beam melting, its dependency on porosity, distance from the base plate and build layer height were investigated. XCT scans of the fatigue sample gauge lengths were correlated to SEM investigations of the fracture surfaces. A comparison between the top and bottom halves of the builds in terms of defect population and fatigue behaviour was also made. Larger pores were detected in samples with a larger build layer height and lower position in the build chamber. Results also indicate that part geometry and pore location, specifically closeness to the surface, are important factors regarding the initiation location of fatigue fractures at 1 % strain. Furthermore, a fatigue critical lack of fusion defect was undetectable in the XCT scan.

Capping protein insulates Arp2/3-assembled actin patches from formins

How actin structures of distinct identities and functions co-exist within the same environment is a critical self-organization question. Fission yeast cells have a simple actin cytoskeleton made of four structures: Arp2/3 assembles actin patches around endocytic pits; the formins For3, Cdc12 and Fus1 assemble actin cables, the cytokinetic ring during division, and the fusion focus during sexual reproduction, respectively. The focus concentrates the delivery of hydrolases by myosin V to digest the cell wall for cell fusion. We discovered that cells lacking capping protein (CP), a heterodimer that blocks barbed-end dynamics and associates with actin patches, exhibit a delay in fusion. Consistent with CP-formin competition for barbed-end binding, Fus1, F-actin and the linear filament marker tropomyosin hyper-accumulate at the fusion focus in absence of CP. However, myosin V and exocytic cargoes are diverted to ectopic foci and reduced at the fusion focus, which underlies the fusion defect. Remarkably, ectopic foci coincide with actin patches, which now contain low levels of Fus1. During mitotic growth, actin patches lacking CP similarly display a dual identity, as they accumulate the formins For3 and Cdc12 and are co-decorated by tropomyosin and the patch marker fimbrin. Thus, CP serves to protect Arp2/3-nucleated structures from formin activity.

Prevalence and possible causes of hypospadias

Hypospadias is the most common congenital malformation of the male external genitalia. After the heart and circulatory system, it is the second most common developmental disorder in males. It is due to a midline fusion defect of the male urethra, which results in a misplaced urethral meatus. Hypospadias may be distal, medial and proximal. It may occur as an isolated defect or it may develop together with other genital disorders (retention of testes in one or both sides, microphallus, bifid scrotum) or with malformation of other organs. In some cases syndromic forms may also occur. Genetic factors play a crucial role in the occurrence of early developmental defect, but endocrine and environmental factors may also be important in the aetiology of hypospadias. It may be associated with various sex and autosomal chromosomal abnormalities. Monogenic and chromosomal causes of hypospadias accounts for about in 30% of all cases, while genetic factors remain unknown in 70% of cases. The authors summarize the development of the male external genitalia, the prevalence and possible causes of hypospadias. They propose that better understanding of the pathogenesis of the disease may contribute to the prevention and decreased prevalence of the disease. Orv. Hetil., 2014, 155(25), 978–985.

A Case Report of Recurrent Fibrosis in Case of Transverse Vaginal Septum

ABSTRACT Transverse vaginal septum is a rare mullerian duct anomaly due to vertical fusion defect. A 21-year-old female presented with secondary amenorrhea and lower abdominal pain for 6 years. She had past history of hematocolpos due to transverse vaginal septum 6 years back and was operated twice for the same. First, the hematocolpos was aspirated, the tract was dilated and evacuation of hematocolpos was done. Fibrosis occurred after 2 months and amenorrhea persisted for 6 years. Second, incomplete resection of the fibrosed transverse vaginal septum was done and a mold was kept for 1 year. On examination, recurrent fibrosis of transverse vaginal septum leading to hematometra and hematocolpos was found. Complete resection of septum with double breasting of vaginal mucosa was done. Drain was kept in vagina for 7 days. Patient was advised to keep the mold for 1 and half year. How to cite this article Paryani D, Desai A, Shah K, Patel SN. A Case Report of Recurrent Fibrosis in Case of Transverse Vaginal Septum. J South Asian Feder Menopause Soc 2014;2(1):42-43.

Congenital Epidermoid Cyst Results in Muscle Fusion Defect in the Upper Lip

Epidermoid cysts are rarely detected malformations in the oral cavity. Their development sites are the sublingual, submaxillary, and submandibular spaces. In this paper, we report a three-month-old infant who was admitted to our hospital due upper lip swelling. Magnetic resonance imaging showed that she had a two-centimeter cystic lesion and fusion defects of orbicularis oris muscle. The cyst was surgically removed and histopathological diagnosis was “epidermoid cyst.” In recent literature, we could not find reports related to orbicularis oris muscle fusion defects because of epidermoid cyst.