Distinctive class of dissipation-induced phase transitions and their universal characteristics

Coupling a system to a nonthermal environment can profoundly affect the phase diagram of the closed system, giving rise to a special class of dissipation-induced phase transitions. Such transitions take the system out of its ground state and stabilize a higher-energy stationary state, rendering it the sole attractor of the dissipative dynamics. In this paper, we present a unifying methodology, which we use to characterize this ubiquitous phenomenology and its implications for the open system dynamics. Specifically, we analyze the closed system's phase diagram, including symmetry-broken phases, and explore their corresponding excitations' spectra. Opening the system, the environment can overwhelm the system's symmetry-breaking tendencies, and changes its order parameter. As a result, isolated distinct phases of similar order become connected, and new phase-costability regions appear. Interestingly, the excitations differ in the newly connected regions through a change in their symplectic norm, which is robust to the introduction of dissipation. As a result, by tuning the system from one phase to the other across the dissipation-stabilized region, the open system fluctuations exhibit an exceptional pointlike scenario, where the fluctuations become overdamped, only to reappear with an opposite sign in the dynamical response function of the system. The overdamped region is also associated with squeezing of the fluctuations. We demonstrate the pervasive nature of such dissipation-induced phenomena in two prominent examples, namely, in parametric resonators and in light-matter systems. Our work draws a crucial distinction between quantum phase transitions and their zero-temperature open system counterparts.ISSN:2643-156

Gelatin/nano-hydroxyapatite hydrogel scaffold prepared by sol-gel technology as filler to repair bone defects

This study reports on the development of a scaffold with a gradient of bioactive solid signal embedded in the biodegradable polymer matrix by combining a sol–gel approach and freeze-drying technology. The chemical approach based on the sol–gel transition of calcium phosphates ensures the particles dispersion into the gelatin matrix and a direct control of interaction among COOHgelatin/Ca2+ ions. Morphological analysis demonstrated that on the basis of the amount of inorganic component and by using specific process conditions, it is possible to control the spatial distribution of nanoparticles around the gelatin helix. In fact, methodology and formulations were able to discriminate between the different hydroxyapatite concentrations and their respective morphology. The good biological response represented by good cell attachment, proliferation and increased levels of alkaline phosphatase as an indicator of osteoblastic differentiation of human mesenchymal stem cells toward the osteogenic lineage, demonstrating the effect of bioactive solid signals on cellular behavior. Furthermore, the inhibition of reactive oxygen species production by composite materials predicted potential anti-inflammatory properties of scaffolds thus confirming their biocompatibility. Indeed, these interesting biological results suggest good potential application of this scaffold as filler to repair bone defects. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2007–2019, 2018

Calixpyrrole Derivatives: “Multi Hydrogen Bond” Catalysts for γ-Butenolide Synthesis

Calix[4]pyrrole (1), calix[2]m-benzo[4]pyrrole (2), 10α,20β- and 10α,20α- bis(4-nitrophenyl)-calix[4]pyrroles 3 and 4, respectively, were found to exhibit various organocatalytic activities in the diastereoselective vinylogous addition reaction of 2-trimethylsilyloxyfuran (TMSOF, 7) to aldehydes. The γ-hydroxybutenolide products are obtained in fairly good yields and with moderate diastereoselectivity. The structures of the catalysts, as well as the reaction conditions, strongly influence the efficiency of the reaction

Osteoinductive and anti-inflammatory properties of chitosan-based scaffolds for bone regeneration

Current bone implants based on new biomaterials may cause a foreign body reaction (FBR) around the implant itself thus prolonging the healing time following bone fractures. In this paper, biomimetic chitosan-based scaffolds promoting bone tissue regeneration and controlling inflammatory response are proposed. First, the anti-inflammatory potential of scaffolds on hMSCs stimulated by lipopolysaccharide (LPS) was investigated by dosing the levels of some interleukins and oxidative stress metabolites (IL-1β, IL-10 and nitrites) involved in immune response. Then, to mimic the inflammation process at osteoporotic site, the effect of scaffolds was evaluated on in vitro co-culture model based on osteoblasts and macrophages stimulated by LPS. Results demonstrated that bioactivated scaffolds are able to i) inhibit synthesis of inflammatory mediators such as IL-1β; ii) reduce oxidative stress metabolites; and iii) promote anti-inflammatory markers generation (IL-10) in hMSCs. Finally, bioactivated scaffolds show an anti-inflammatory activity also on in vitro co-cultures, which better mimic in vivo damaged bone microenvironment