Laser cutting of different polymeric plastics (PE, PP and PC) by a CO2 laser beam

Thiswork investigates the application of theCO2 laser cutting process to three thermoplastic polymers, polyethylene (PE), polypropylene (PP), polycarbonate (PC) in different thicknesses ranging from 2 to 10 mm. The process parameters examined were: laser power, range of cutting speed, type of focusing lens, pressure and flow of the covering gas, thickness of the samples. Furthermore, the values of kerf widths on top (Lsup) and bottom (Linf ) thicknesses, the melted transverse area, the melted volume per unit time and surface roughness values (Ra) on cut edges were also measured

On the welding of different materials by diode laser

In technical literature, there are few papers about the use of diode lasers in material processing and particularly in metal welding. In this paper, different materials, according to specific and particular industrial needs and requests, have been tested with a welding process by a diode laser, emitting a 808 nm laser radiation. Beads on plate have been studied. The goal was to evaluate the maximum weldable thickness and define the best process parameters for each material. The experimental evaluation has been carried out considering the following parameters: power level, welding speed (WS), shielding gas, gas nozzle and orientation of the focused elliptical spot as to the welding direction

Small fragments sodium sulfated hyaluronate, more than hyaluronic acid, reduces LPS-induced cytokine/chemokine levels in HaCaT cells

Hyaluronic acid (HA) is a linear non-sulphated glycosaminoglycan, used in dermatology as a biomaterial for bioengineering purposes, temporary dermal filler, stimulation of wound healing as well as drug vehicle in topical formulations. In addition to the well-characterized structural properties, extensive research on HA has revealed a range of vastly immunemodulatory effects, dependent on its size. In this in vitro study we investigated the ability of HA-S3, a small fragment HA (MW, molecular weight: 68 kDa) with degree of sulphatation of 3 and of HA fraction (MW:210 kDa) to reduce the bacterial induced inflammatory response in spontaneous immortalized keratinocytes. To this purpose, HaCaT cells were treated for 24 hours with 25 µg/ml of E. Coli derived bacterial lipopolysaccharide (LPS) in absence or presence of small fragment HA-S3 or HA. Cell viability was thereafter assessed using trypan blue stain and interleukin (IL)-8, IL-1β and tumor necrosis factor alpha (TNF-α) concentrations were determined in cell supernatants by single enzyme-linked immunoadsorbent assay (ELISA). Our results showed that cell viability was not affected either by HA-S3 or HA which in turn were able to reduce LPS-induced mortality. HA and especially HA-S3 were able to significantly reduce LPS-induced pro-inflammatory cytokines. Our observation might suggest new perspectives in the development of HA-S3 containing topical products able to modulate cutaneous inflammatory response

redesign and manufacturing of a metal towing hook via laser additive manufacturing with powder bed

Abstract An approach to redesign and manufacture a metal towing hook via Selective Laser Melting is discussed. Some reference criteria and general guidelines are considered step-by-step to concurrently address lightening, manufacturability and job planning. Grounds are given for the application of Additive Manufacturing for complex components to the purpose of material saving and increased safety factor

Fatigue assessment of Ti-6Al-4V titanium alloy laser welded joints in absence of filler material by means of full-field techniques

The aim of this research activity was to study the fatigue behavior of laser welded joints of titanium alloy, in which the welding was performed using a laser source and in the absence of filler material, by means of unconventional full field techniques: Digital Image Correlation (DIC), and Infrared Thermography (IRT). The DIC technique allowed evaluating the strain gradients around the welded zone. The IRT technique allowed analyzing the thermal evolution of the welded surface during all the fatigue tests. The fatigue limit estimated using the Thermographic Method corresponds with good approximation to the value obtained from the experimental fatigue tests. The obtained results provided useful information for the development of methods and models to predict the fatigue behavior of welded T-joints in titanium alloy

A Modular Regularized Variational Multiscale Proper Orthogonal Decomposition for Incompressible Flows

In this paper, we propose, analyze and test a post-processing implementation of a projection-based variational multiscale (VMS) method with proper orthogonal decomposition (POD) for the incompressible Navier-Stokes equations. The projection-based VMS stabilization is added as a separate post-processing step to the standard POD approximation, and since the stabilization step is completely decoupled, the method can easily be incorporated into existing codes, and stabilization parameters can be tuned independent from the time evolution step. We present a theoretical analysis of the method, and give results for several numerical tests on benchmark problems which both illustrate the theory and show the proposed method's effectiveness

Coronary covered stents

Covered stents offer an effective bail-out strategy in vessel perforations, are an alternative to surgery for the exclusion of coronary aneurysms, and have a potential role in the treatment of friable embolisation-prone plaques. The aim of this manuscript is to offer an overview of currently available platforms and to report results obtained in prior studies

Optical coherence tomography guidance for percutaneous coronary intervention with bioresorbable scaffolds

Background The effect of optical coherence tomography (OCT) guidance on the implantation strategy during all phases of percutaneous coronary intervention (PCI) with bioresorbable vascular scaffolds (BVSs) in a real-world scenario has been poorly investigated. Methods Consecutive patients undergoing BVS implantation at our institution were included in this registry. Frequency-domain OCT pullbacks were performed at the operator's discretion during all phases of BVS implantation procedures to optimize preparation of lesions, confirm BVS size, and optimize expansion and apposition of scaffolds. Results Between September 2012 and July 2015, 203 BVSs were implanted in 101 consecutive patients at our institution (2.01 BVSs/patient). In 66 patients, the procedure was performed under OCT guidance. In the OCT subgroup, 66 (77.6%) of the 85 treated lesions were complex (B2/C AHA/ACC type). Overall, 147 OCT pullbacks were performed and 72/147 (49.0%) pullbacks indicated the need for changing strategy. After angiography-only-guided optimisation of BVS in 27 (31.8%) lesions, an OCT examination prompted performance of a second post-expansion. This resulted in an increase in the minimal scaffold area (5.5 to 6.3\ua0mm2, p\ua0=\ua00.004) and a decrease in the incomplete scaffold apposition area (1.1 to 0.6\ua0mm2, p\ua0=\ua00.082), with no new stent fractures. When the population was divided according to the time of BVS implantation, an initial learning adaptation became evident, with the number of OCT-guided changes in strategy significantly decreasing between the initial and final time periods (p\ua0=\ua00.017). Conclusions OCT guidance for BVS implantation significantly affects the procedural strategy, with favourable effects on acute results and the learning curve