Towards a numerical simulation of direct manufacturing of thermoplastic parts by powder laser sintering COMPLAS XI

Direct manufacturing technology using Selective Laser Sintering (SLS) on thermoplastic powders allows obtaining final parts in a short time, with classical polymer density and a high flexibility of shape and evolution of parts. The physical base of this process is the coalescence of grains, which initiates the densification of powder during SLS. This study presents a 2D C-NEM simulation of the whole process. We firstly focus on the chosen method and its advantages. We present the simulation details and validate the modeling through a 2D infinite cylinders coalescence simulation. The mesh of the grain interface is continuously adapted to the local curvature to better capture the coalescence phenomenon. We are able to simulate the sintering of twelve particles laying on a support within some hours

In situ generation of coronal Alfvén waves by jets

Within the framework of 3D resistive magnetohydrodynamic, we simulate the formation of a plasma jet with the morphology, upward velocity up to 130 km s−1, and time-scale formation between 60 and 90 s after beginning of simulation, similar to those expected for type II spicules. Initial results of this simulation were published in paper by, e.g. González-Avilés et al. (2018), and present paper is devoted to the analysis of transverse displacements and rotational-type motion of the jet. Our results suggest that 3D magnetic reconnection may be responsible for the formation of the jet in paper by González-Avilés et al. (2018). In this paper, by calculating times series of the velocity components vx and vy in different points near to the jet for various heights we find transverse oscillations in agreement with spicule observations. We also obtain a time-distance plot of the temperature in a cross-cut at the plane x = 0.1 Mm and find significant transverse displacements of the jet. By analysing temperature isosurfaces of 104 K with the distribution of vx, we find that if the line-of-sight (LOS) is approximately perpendicular to the jet axis then there is both motion towards and away from the observer across the width of the jet. This red–blue shift pattern of the jet is caused by rotational motion, initially clockwise and anti-clockwise afterwards, which could be interpreted as torsional motion and may generate torsional Alfvén waves in the corona region. From a nearly vertical perspective of the jet the LOS velocity component shows a central blue-shift region surrounded by red-shifted plasma

A novel human skin chamber model to study wound infection ex vivo

Wound infections with multi-drug resistant bacteria increase morbidity and mortality and have considerable socioeconomic impact. They can lead to impaired wound healing, resulting in rising treatment costs. The aim of this study was to investigate an ex vivo human wound infection model. Human full-thickness skin from the operating room (OR) was placed into the Bo-Drum® and cultivated for 7 days in an air–liquid interphase. On day 8, the skin was inoculated with either (1) Pseudomonas aeruginosa, (2) Staphylococcus aureus (105 CFU, n = 3) or (3) carrier control. 1, 3 and 7 days after inoculation colony forming units in the tissue/media were determined and cytokine expression was quantified. A reliable and reproducible wound infection could be established for 7 days. At this timepoint, 1.8 × 108 CFU/g tissue of P. aeruginosa and 2 × 107 CFU/g tissue of S. aureus were detected. Immunohistochemical analysis demonstrated bacterial infection and epidermolysis in infected skin. RT-PCR analysis exhibited a significant induction of proinflammatory cytokines after infection. The BO-drum® is a robust, easy-to-use, sterilizable and reusable ex vivo full-skin culture system. For investigation of wound infection, treatment and healing, the BO-drum® presents a convenient model and may help to standardize wound research

Triggered crustal earthquake swarm across subduction segment boundary after the 2016 Pedernales, Ecuador megathrust earthquake

Megathrust ruptures and the ensuing postseismic deformation cause stress changes that may induce seismicity on upper plate crustal faults far from the coseismic rupture area. In this study, we analyze seismic swarms that occurred in the north Ecuador area of Esmeraldas, beginning two months after the 2016 M$_{w}$ 7.8 Pedernales, Ecuador megathrust earthquake. The Esmeraldas region is 70 km from the Pedernales rupture area in a separate segment of the subduction zone. We characterize the Esmeraldas sequence, relocating the events using manual arrival time picks and a local a-priori 3D velocity model. The earthquake locations from the Esmeraldas sequence outline an upper plate fault or shear zone. The sequence contains one major swarm and several smaller swarms. Moment tensor solutions of several events include normal and strike-slip motion and non-double-couple components. During the main swarm, earthquake hypocenters increase in distance from the first event over time, at a rate of a few hundred meters per day, consistent with fluid diffusion. Events with similar waveforms occur within the sequence, and a transient is seen in time series of nearby GPS stations concurrent with the seismicity. The events with similar waveforms and the transient in GPS time series suggest that slow aseismic slip took place along a crustal normal fault during the sequence. Coulomb stress calculations show a positive Coulomb stress change in the Esmeraldas region, consistent with seismicity being triggered by the Pedernales mainshock and large aftershocks. The characteristics of the seismicity indicate that postseismic deformation involving fluid flow and slow slip activated upper plate faults in the Esmeraldas area. These findings suggest the need for further investigation into the seismic hazard potential of shallow upper plate faults and the potential for megathrust earthquakes to trigger slow-slip and shallow seismicity across separate segments of subduction zones