Effects of Curing on Photosensitive Resins in {SLA} Additive Manufacturing

Different mechanical properties characterise the materials of 3D printed components, depending on the specific additive manufacturing (AM) process, its parameters, and the post-treatment adopted. Specifically, stereolithography (SLA) uses a photopolymerisation technique that creates solid components through selective solidification. In this study, 72 specimens were 3D printed using 12 commercial-grade methacrylate resins and tested under uniaxial tensile loads. The resin specimens were evaluated before and after curing. The recommended cure temperature and time were followed for all materials. The stress-strain curves measured during the testing campaign were evaluated in terms of maximum tensile strength, Young’s modulus, ductility, resilience, and toughness. The results reveal that the curing process increases the material stiffness and resistance to tensile loads. However, it was found that the curing process generally reduces the plasticity of the resins, causing a more or less marked brittle behaviour. This represents a potential limitation to the use of SLA 3D printing for structural elements which require some plasticity to avoid dangerous sudden failures

Reactive oxygen intermediates mediate angiotensin II-induced c-Jun.c-Fos heterodimer DNA binding activity and proliferative hypertrophic responses in myogenic cells

Angiotensin II (Ang-II) receptor engagement activates many immediate early response genes in both vascular smooth muscle cells and cardiomyocytes whether a hyperplastic or hypertrophic response is taking place. Although the signaling pathways stimulated by Ang-II in different cell lines have been widely characterized, the correlation between the generation of different second messengers and specific physiological responses remains relatively unexplored. In this study, we report how in both C2C12 quiescent myoblasts and differentiated myotubes Ang-II significantly stimulates AP1-driven transcription and c-Jun.c-Fos heterodimer DNA binding activity. Using a set of different protein kinase inhibitors, we could demonstrate that Ang-II-induced increase in AP1 binding is not mediated by the cAMP-dependent pathway and that both protein kinase C and tyrosine kinases are involved. The observation that in quiescent myoblasts Ang-II increase of AP1 binding and induction of DNA synthesis and, in differentiated myotubes, Ang-II stimulation of protein synthesis are abolished by the cysteine-derivative and glutathione precursor N-acetyl-L-cysteine strongly suggests a role for reactive oxygen intermediates in the intracellular transduction of Ang-II signals for immediate early gene induction, cell proliferation, and hypertrophic responses

Effects of Curing on Photosensitive Resins in {SLA} Additive Manufacturing

Different mechanical properties characterise the materials of 3D printed components, depending on the specific additive manufacturing (AM) process, its parameters, and the post-treatment adopted. Specifically, stereolithography (SLA) uses a photopolymerisation technique that creates solid components through selective solidification. In this study, 72 specimens were 3D printed using 12 commercial-grade methacrylate resins and tested under uniaxial tensile loads. The resin specimens were evaluated before and after curing. The recommended cure temperature and time were followed for all materials. The stress-strain curves measured during the testing campaign were evaluated in terms of maximum tensile strength, Young’s modulus, ductility, resilience, and toughness. The results reveal that the curing process increases the material stiffness and resistance to tensile loads. However, it was found that the curing process generally reduces the plasticity of the resins, causing a more or less marked brittle behaviour. This represents a potential limitation to the use of SLA 3D printing for structural elements which require some plasticity to avoid dangerous sudden failures

Effects of the Manufacturing Methods on the Mechanical Properties of a Medical-Grade Copolymer Poly(L-Lactide-co-D,L-Lactide) and Poly(L-Lactide-co-ɛ-Caprolactone) Blend

11openopenMariana Rodriguez Reinoso; Marco Civera; Vito Burgio; Annalisa Chiappone; Oliver Grimaldo Ruiz; Alessandra D'Anna; Carmela Riccio; Ignazio Roppolo; Alberto Frache; Paola Antonaci; Cecilia SuraceRODRIGUEZ REINOSO, Mariana; Civera, Marco; Burgio, Vito; Chiappone, Annalisa; GRIMALDO RUIZ, Oliver; D'Anna, Alessandra; Riccio, Carmela; Roppolo, Ignazio; Frache, Alberto; Antonaci, Paola; Surace, Cecili

Universal Behavior of Lyapunov Exponents in Unstable Systems

We calculate the Lyapunov exponents in a classical molecular dynamics framework. The system is composed of few hundreds particles interacting either through Yukawa (Nuclear) or Slater-Kirkwood (Atomic) forces. The forces are chosen to give an Equation of State that resembles the nuclear and the atomic $^4He$ Equation Of State respectively near the critical point for liquid-gas phase transition. We find the largest fluctuations for an initial "critical temperature". The largest Lyapunov exponents $\lambda$ are always positive and can be very well fitted near this "critical temperature" with a functional form $\lambda\propto |T-T_c|^{-\omega}$, where the exponent $\omega=0.15$ is independent of the system and mass number. At smaller temperatures we find that $\lambda\propto T~ ^{0.4498}$, a universal behavior characteristic of an order to chaos transition.Comment: 11 pages, RevTeX, 3 figures not included available upon reques

Chaos and Statistical Mechanics in the Hamiltonian Mean Field Model

We study the dynamical and statistical behavior of the Hamiltonian Mean Field (HMF) model in order to investigate the relation between microscopic chaos and phase transitions. HMF is a simple toy model of $N$ fully-coupled rotators which shows a second order phase transition. The canonical thermodynamical solution is briefly recalled and its predictions are tested numerically at finite $N$. The Vlasov stationary solution is shown to give the same consistency equation of the canonical solution and its predictions for rotator angle and momenta distribution functions agree very well with numerical simulations. A link is established between the behavior of the maximal Lyapunov exponent and that of thermodynamical fluctuations, expressed by kinetic energy fluctuations or specific heat. The extensivity of chaos in the $N \to \infty$ limit is tested through the scaling properties of Lyapunov spectra and of the Kolmogorov-Sinai entropy. Chaotic dynamics provides the mixing property in phase space necessary for obtaining equilibration; however, the relaxation time to equilibrium grows with $N$, at least near the critical point. Our results constitute an interesting bridge between Hamiltonian chaos in many degrees of freedom systems and equilibrium thermodynamics.Comment: 19 pages, 10 postscript figures included, Latex, Elsevier macros included. Invited talk at the conference ``Classical Chaos and its quantum manifestations'' in honour of Boris Chirikov, Sputnik conference of STATPHYS 20 - Toulouse, France - July 16-18, 1998. Revised version (added refs, changed part of the text and some figures) accepted for publication in Physica

Hsp60 Is Actively Secreted by Human Tumor Cells

Background: Hsp60, a Group I mitochondrial chaperonin, is classically considered an intracellular chaperone with residence in the mitochondria; nonetheless, in the last few years it has been found extracellularly as well as in the cell membrane. Important questions remain pertaining to extracellular Hsp60 such as how generalized is its occurrence outside cells, what are its extracellular functions and the translocation mechanisms that transport the chaperone outside of the cell. These questions are particularly relevant for cancer biology since it is believed that extracellular chaperones, like Hsp70, may play an active role in tumor growth and dissemination. Methodology/Principal Findings: Since cancer cells may undergo necrosis and apoptosis, it could be possible that extracellular Hsps are chiefly the result of cell destruction but not the product of an active, physiological process. In this work, we studied three tumor cells lines and found that they all release Hsp60 into the culture media by an active mechanism independently of cell death. Biochemical analyses of one of the cell lines revealed that Hsp60 secretion was significantly reduced, by inhibitors of exosomes and lipid rafts. Conclusions/Significance: Our data suggest that Hsp60 release is the result of an active secretion mechanism and, since extracellular release of the chaperone was demonstrated in all tumor cell lines investigated, our observations most likel

Cure indicators and prevalence by stage at diagnosis for breast and colorectal cancer patients: A population‐based study in Italy

People alive many years after breast (BC) or colorectal cancer (CRC) diagnoses are increasing. This paper aimed to estimate the indicators of cancer cure and complete prevalence for Italian patients with BC and CRC by stage and age. A total of 31 Italian Cancer Registries (47% of the population) data until 2017 were included. Mixture cure models allowed estimation of net survival (NS); cure fraction (CF); time to cure (TTC, 5-year conditional NS >95%); cure prevalence (who will not die of cancer); and already cured (prevalent patients living longer than TTC). 2.6% of all Italian women (806,410) were alive in 2018 after BC and 88% will not die of BC. For those diagnosed in 2010, CF was 73%, 99% when diagnosed at stage I, 81% at stage II, and 36% at stages III-IV. For all stages combined, TTC was >10 years under 45 and over 65 years and for women with advanced stages, but <= 1 year for all BC patients at stage I. The proportion of already cured prevalent BC women was 75% (94% at stage I). Prevalent CRC cases were 422,407 (0.7% of the Italian population), 90% will not die of CRC. For CRC patients, CF was 56%, 92% at stage I, 71% at stage II, and 35% at stages III-IV. TTC was <= 10 years for all age groups and stages. Already cured were 59% of all prevalent CRC patients (93% at stage I). Cancer cure indicators by stage may contribute to appropriate follow-up in the years after diagnosis, thus avoiding patients' discrimination