micro structuring of titanium collectors by laser ablation technique a promising approach to produce micro patterned scaffolds for tissue engineering applications

Abstract Multi-scale micro-structured scaffolds can sustain attachment and orientation of different cells phenotypes. An innovative use of laser ablation technique to build micro-structured titanium surfaces to be used as collectors in both electrophoretic deposition and electrospinning processes was investigated. To produce micro-patterned scaffolds, a negative replica patterning was exploited by designing specific patterns to be laser ablated on titanium plates. This method allows the deposition of the scaffolds on the mold, thus reproducing the micro-features on the scaffold surface. The titanium surface morphology depending on ablation parameters was studied and the capability of the process in replicating the micro-pattern was characterized

SWARM Optimization of Force Model Parameters in Micromilling

Because of the improvement of machine-tool and tool performances in micro cutting field, the interest on these processes is increasing. Therefore, researchers involved in micro manufacturing processes focused their attention on these types of processes with the aim of improving the knowledge on the phenomena occurring during micro cutting operations. The objective of this work is to develop a modelling procedure for forecasting cutting forces in micromilling considering the tool run-out and the cutting tool geometry. The designed modelling procedure combines information coming from a force model, an optimization strategy and some experimental tests. The implemented force model is based on specific cutting pressure and actual instantaneous chip section. The tool run-out and the cutting tool geometry were considered in the analytical model. The adopted optimization strategy was based on the Particles Swarm strategy due to its suitability in solving analytical non-linear models. The experimental tests consisted in realizing micro slots on a sample made of Ti6Al4V. The comparison between experimental and analytical data demonstrates the good ability of the proposed procedure in correctly defining the model parameters

Finite element simulation of high speed micro milling in the presence of tool run-out with experimental validations

Micro milling process of CuZn37 brass is considered important due to applications in tool production for micro moulding and micro replication technology. The variations in material properties, work material adhesion to tool surfaces, burr formation, and tool wear result in loss of productivity. The deformed chip shapes together with localized temperature, plastic strain, and cutting forces during micro milling process can be predicted using finite element (FE) modeling and simulation. However, toolworkpiece engagement suffers from tool run-out affecting process performance in surface generation. This work provides experimental investigations on effects of tool run-out as well as process insight obtained from simulation of chip flow, with and without considering tool run-out. Scanning electron microscope (SEM) observation of the 3D chip shapes demonstrates ductile deformed surfaces together with localized serration behavior. FE simulations are utilized to investigate the effects of micro milling operation, cutting speed, and feed rate on forces, chip flow, and shapes. Predicted cutting forces and chip flow results from simulations are compared with force measurements, tool run-out, and chip morphology revealing reasonable agreements

Multi-layered Scaffolds Production via Fused Deposition Modeling (FDM) Using an Open Source 3D Printer: Process Parameters Optimization for Dimensional Accuracy and Design Reproducibility

Abstract One of the most applied strategies in tissue engineering consists in the development of 3D porous scaffolds with similar composition to the specific tissue. In fact, the microstructure of the scaffolds influences the final structure of the in growing tissue. In this study, multi-layered PCL scaffolds were produced with modified Fab@home FDM printer in order to analyze the influence of the extrusion technology (filament or powder extrusion head) and of the process parameters on the deposited material. In particular, dimensions and uniformity of both deposited filament and grid of the scaffolds were analyzed to understand the influence of the process parameters so as to optimize the FDM production technology

The spectrum of small-bowel lesions of AL-type amyloidosis at capsule endoscopy

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Laparoscopic splenectomy for splenic hamartoma : a case report

Hamartoma is a rare splenic benign tumor usually accidentally detected as a radiologic finding. Preoperative diagnosis poses a challenge and thus surgery becomes necessary to confirm the clinical suspicion. Laparoscopic splenectomy has gained consensus as a standard surgical procedure particularly for autoimmune hematological diseases. This former experience has allowed this technique to be extended to other splenic pathologies. Here we report a case of total laparoscopic splenectomy for a bulky splenic hamartoma in a young male patien

Study of void closure in hot rolling of stainless steel slabs

Continuous casting products contain void defects due to the shrinkage occurring during solidification. These defects, having different and irregular shapes and sizes, are located and distributed within the material depending on casting conditions. In order to deliver safe and sound products, these voids must be reduced during the subsequent hot forming processes, but it becomes very difficult when slabs are directly hot rolled without any previous forming processes (i.e., cogging), so obtaining a cheaper and more sustainable process chain. Many studies on voids closure present in literature are based on the evaluation of a process parameter called "stress triaxiality ratio". Aim of this research is to optimize the hot rolling process performed to reduce shrinkage voids of the billet due to casting. In particular, the results of a study on voids closure during hot rolling of stainless steel slabs (AISI 316L) coming from continuous casting process are reported. A FE analysis of the effects of the main process parameters of hot rolling on the "voids closure index" were investigated. Afterwards, experimental tests were performed to validate the research from an industrial point of view. A correlation between the void closure index and the final residual void percentage along the rolled slabs was found

The Great Pretender : Rectal Syphilis Mimic a Cancer

Rectal syphilis is a rare expression of the widely recognised sexual transmitted disease, also known as the great imitator for its peculiarity of being confused with mild anorectal diseases because of its vague symptoms or believed rectal malignancy, with the concrete risk of overtreatment. We present the case of a male patient with primary rectal syphilis, firstly diagnosed as rectal cancer; the medical, radiological, and endoscopic features are discussed below

Valutazione della formabilità di lamiere di titanio a freddo e a tiepido

Il lavoro descrive i risultati di prove di trazione e di prove di formabilità limite Nakazima effettuatea temperatura ambiente e a tiepido (300°C) utili per lo sviluppo di un modello simulativo per la valutazionedella fattibilità di un elemento di geometria complessa per l’industria automobilistica, da realizzare in lamieradi titanio commercialmente puro. Si dimostra come le caratteristiche del materiale considerato, espressein termini di legge di flusso e di formabilità, cambino al variare della temperatura di lavorazione rendendofattibile o meno il prodotto. Il modello FEM e l’applicazione delle curve di flow stress e di formabilità limite(FLC) sono state validate tramite simulazione preliminare delle prove Nakazima stesse.L’approccio proposto è particolarmente adatto per definire, in ambiente virtuale, geometria e parametridi processo per operazioni di stampaggio su materiali innovativi difficilmente deformabili a temperaturaambiente e consente notevoli risparmi di tempo e di costo, evitando operazioni di “trial-and-error”normalmente utilizzate nella fase di setup del processo produttivo