Thin-Walled Tube Made of AZ31 Magnesium Alloy Fabricated by New Compound Extrusion Including Direct Extrusion and Multi-pass Bending

A new severe plastic deformation for manufacturing thin-walled tube made of AZ31 magnesium alloy called TEB(Tube-Extrusion-Bending ) process, which combines direct extrusion with two step bending,has been developed to manufacture tube.The TEB process has been researched by using finite element modeling (FEM) method. The rules of extrusion temperatures and the extrusion forces varying with process parameters have been developed. A TEB process with installed containers and dies has been constructed to perform tests in order to validate the FEM model with different process conditions. And the microstructures evolution have been researched based on effective strains evolution. The results showed that refined and uniform microstructures can be achieved by TEB process. The research results showed that the TEB process would produce the serve plastic deformation and improve the recrystallization of the grains.The comparisons of FEM simulation and experimental results have been made to obtain the relative important principles of TEB process.

Numerical assessment of large hexagonal seamless steel tube extrusion feasibility

The study assesses feasibility of hot extrusion of a large seamless hexagonal 9%Cr-1%Mo steel tube. The manufacturing chain starts from a pierced cylindrical billet, hot extruded and to be further cold drawn in several passes. Preliminary industrial tests have shown thickness reduction in extrusion limited by a huge initial force peak (+25 %) reaching the press capacity. To understand this force peak, thermomechanical numerical simulation (ForgeNxt®) of the furnace-press transfer and extrusion stages is carried out. Constitutive model at high temperature, high strain and strain rate has been selected from literature. Surface properties, namely Heat Transfer Coefficient (HTC) and friction coefficient, have been made space- and time-dependent to represent glass lubrication. Numerical results are qualitatively compared to industrial experimental values to evaluate the prediction of the model. It suggests that the difficult start of the glass melting and flow along a cooled die affects the force peak. Practical improvements are suggested on this basis, together with possible refinements of the simulation for more precision and insight into extruded tube quality.

Factors Related to Ventilation Tube Extrusion Time in Children and Adults

Background and Objective: The aim of this study was to investigate the factors affecting extrusion time in both children and adults with ventilation tube (VT) insertion, providing useful information for clinicians for better decision-making, follow strategy, and potentially improve clinical outcomes for these patients. Methods: Data from patients receiving myringotomy with VT insertion from January 1, 2007, to June 30, 2012, were retrospectively collected and analyzed by the end of 2018. Various factors, including age, gender, history of VT insertion, tympanogram, size of VT used, local finding of tympanic membrane, hypertension, diabetes mellitus, hyperlipidemia, and postoperative ear infection, were included and analyzed to examine the effects of these factors on extrusion time. Results: A total of 447 patients were included in this study (Child group–Adult group = 237:210). The overall average extrusion time was 225.85 days. In the subgroup analysis, the average time was 221.3 days and 231.0 days for children and adults, respectively. The results showed that the VT extrusion time was significantly longer in participants without a history of VT insertion and in those where larger sized VTs were inserted in both age-groups. Male gender had an influence on extrusion time in children. In addition, a history of VT insertion and VT size were determined to be factors related to extrusion before 12 months in children. Conclusion: History of VT insertion and VT size were significantly related to VT extrusion time in both children and adults and defined as factors associated with extrusion before 12 months in children. The findings suggest avoiding VT with a diameter < 1 mm and considering an appropriately larger size in patients with a history of VT insertion to optimize VT retention.

Subannular Tubes in Children With Cleft Palate

Objective: To investigate subannular tube (SAT) placement as an alternative treatment of chronic middle ear disease in children with cleft palate. Design: Retrospective cohort study. Participants: All children with cleft palate with intractable otitis media with effusion and/or with tympanic membrane retraction, operated for insertion of 1 or more sets of transtympanic tubes followed by SAT in a tertiary center. Main Outcome Measures: Audiological outcomes, average duration of tubes, and postoperative complications were analyzed. Results: This study included 21 children with cleft palate, aged 3 to 14 years. A total of 38 ears was evaluated. The median time of follow-up was 42 months. During follow-up, 69.2% of the patients had no complications. Observed complications were otorrhea (13.5%) and tube obstruction (7.7%). In 7.9% of the cases, otitis media with effusion relapsed after tube extrusion. By the end of the study, 76.3% of the tubes remained in situ and 68.4% of the tympanic membranes had the SAT in place and had no significant alterations. The mean duration of SATs was 16 months, which was significantly superior to transtympanic tube duration. A significant sustained improvement in the hearing of children with SATs was observed. Conclusion: Subannular tube insertion results in hearing improvement to normal range and tympanic retraction pockets reversion in children with cleft palate with persistent otitis media with effusion and tympanic retraction/atelectasis. This surgery appears to be safe and provides long-term efficient middle ear aeration. Strict postoperative follow-up is crucial for the success of the treatment.

Dacryocystectomy with Lacrimal Silicone Intubation in Challenging Patients Affected by Recurrent Dacryocystitis and Epiphora: Expanding Minimally Invasive Approach Indications

Objective: In this study, we evaluated the feasibility and safety of dacryocystectomy associated with lacrimal intubation, for the treatment of recurrent dacryocystitis and epiphora secondary to lacrimal obstruction with compromised lacrimal sac, was evaluated. Subjects and Methods: 32 patients underwent dacryocystectomy with Crawford tubes canalicular insertion, performed by a single surgeon. Post-operative visits were scheduled at 1st and 10th day, 1, 3, and 6 months. At each follow-up visit, the prevalence of epiphora and dacryocystitis was evaluated and compared with baseline data. Also, we evaluated the prevalence of local and systemic post-operative adverse events during the follow-up period. Results: 11 patients (34.38%) reported persistent epiphora, which lasted for 30 days after surgery. Among them, 9 subjects (28.13%) complained occasional epiphora even at the six months follow-up. In the event of dacryocystitis or subacute phlogosis before surgery, patients reported a definitive symptom resolution. Other reported adverse events were epithelial corneal erosion due to Crawford tube protrusion (4 cases, 12.5%), a Crawford tube extrusion case (3.13%), 3 cases of surgical wound dehiscence (9.36%), and a case of mild local bleeding persisting for 15 days Conclusion: A significative epiphora reduction was observed after surgery with an acceptable safety profile, expanding dacryocystectomy indications. This procedure provides a satisfactory resolution of recurrent dacryocystitis. However, this approach should be performed only in well-selected cases: elderly/frail patients with altered lacrimal sacs, epiphora associated with recurrent infections, and failure after dacryocystectomy.

Influence of membrane-cortex linkers on the extrusion of membrane tubes

The cell membrane is an inhomogeneous system composed of phospholipids, sterols and proteins that can be directly attached to underlying cytoskeleton. The linkers between the membrane and the cytoskeleton are believed to have a profound effect on the mechanical properties of the cell membrane and its ability to reshape. Here we investigate the role of membrane-cortex linkers on the extrusion of membrane tubes using computer simulations and experiments. In simulations we find that the force for tube extrusion has a non-linear dependence on the density of membrane-cortex attachments: at a wide range of low and intermediate densities of linkers the force is not significantly influenced by the presence of membrane linking proteins and resembles that of the bare membrane. For large concentrations of linkers however the force substantially increases compared to the bare membrane. In both cases the linkers provided membrane tubes with increased stability against coalescence. We then pulled tubes from HEK cells using optical-tweezers for varying expression levels of the membrane-cortex attachment protein Ezrin. In line with simulations, we observed that overexpression of Ezrin led to an increased extrusion force, while Ezrin depletion had negligible effect on the force. Our results shed new light on the importance of local effects in membrane reshaping at the nanoscopic scales.