Process study of the formation of biodegradable polymer microspheres for tissue engineering

A series of polymer microspheres was prepared via solvent evaporation by dispersing dichloromethane solutions of polylactic-co-glycolic acid (PLGA) in water. The dimensions of the final dry particles were measured by laser diffraction and correlated to the main fluid-dynamic parameters of the dispersion process, namely viscosity ratio, volume fraction of dispersed phase, intensity of stirring, and Weber number (We). Data analysis indicated that the system under study can be quantitatively well described by empirical models present in the literature and concerning the dispersion of liquid-liquid immiscible systems. The PLGA microspheres obtained in this way may be employed for fabrication of biodegradable scaffolds for tissue engineering

Thermo-Hydrodynamic Analysis of Plain and Tilting Pad Bearings

Abstract The demand for higher efficiency and increased equipment compactness is pushing industrial compressors' designers towards the choice of higher rotor peripheral speed. As a consequence, modern bearing-rotor systems are subject to complex thermal phenomena inducing a renewed interest on their real working conditions. This work is about the validation of the in-house numerical code TILTPAD developed at the Department of Industrial Engineering of the University of Florence for the thermo-hydrodynamic analysis of both plain and tilting pad journal bearings performance. TILTPAD is a steady-state code based on a 2D thin-film approach able to find either the resulting hydrodynamic load using the shaft equilibrium position and the rotational speed (i.e., direct problem) or the shaft equilibrium position once the load and the rotational speed are prescribed (i.e., inverse problem). In order to calculate pads' pressure distribution a finite element approach is used to solve the Reynolds equation together with a mixed procedure to evaluate pads equilibrium positions. Two steady-state energy equations based on a Petroff-type simplification are implemented in the code. The first one is proposed in the work of Balbahadur and Kirk [1] while the second one is based on an improved mixing model and a temperature dependent viscosity. An iterative procedure is used between Reynolds and energy equations to account for the dependence of the dynamic viscosity on the temperature field. Super-laminar flow regimes are also modeled in the code by means of a simplified approach able to represents, with reasonable accuracy, the effects of Taylor-Couette vortex flows and of the transitional regimes up to the onset of a fully turbulent state. Under these hypotheses, the pressure field is slightly affected by the viscosity variation while dissipative effects are enhanced. The code has been validated by means of comparison with available experimental data. Particular attention is devoted to static working parameters (i.e., equilibrium position and frictional power loss), reproducing the global behavior of the bearing, although some local characteristic is also considered

On the development of an efficient regenerative compressor

AbstractRegenerative compressors are attractive machines used in several industrial processes. Their main characteristic is the highly three-dimensional development of the flow. Consequently, usual approach for axial or centrifugal compressors design are not an affordable strategy. The analysis of the rotor/stator coupling is the main issue in the design of regenerative compressors because of the vane-less nature of the stator and the characteristic trajectory of the flow. This paper describes the design of an efficient regenerative compressor based on a highly detailed Reynolds Averaged Navier-Stokes (RANS) analysis. The targets of the activity are defined in terms of expected mass-flow, pressure rise and compressor efficiency, and then a preliminary design is performed using an in-house mono-dimensional tool based on simplified assumptions for the nominal operating conditions. Once the model provided the most promising geometrical characteristics for the target operating point, three-dimensional steady RANS analyses are performed to evaluate the actual performance of the compressor for a wide range of mass-flow values. Special attention has been paid to the generation of the computational mesh and a specific solution for the rotor row has been developed. Compressibility effects are non-negligible since the flow Mach number is higher than 0.5 in several compressor sections, including the leakage zone regions where the losses are higher. The rotor and the full compressor efficiencies are evaluated and discussed to underline the importance of the rotor/volute coupling. The flow behaviour inside of the volute as well as the distribution of losses is also discussed and some guidelines for the efficient design of regenerative compressors are presented

Tocilizumab Effects on Coagulation Factor XIII in Patients with Rheumatoid Arthritis

Introduction: Rheumatoid arthritis (RA) is a chronic systemic auto-immune disease associated with a prothrombotic state. Tocilizumab, an interleukin-6 receptor inhibitor, is highly effective in controlling disease activity and thrombotic risk. Factor XIII (FXIII), involved in thrombotic complications, has been reported to be reduced in RA patients during maintenance treatment with tocilizumab, but no data are available before and after the drug administration. Thus, we investigated the effects of tocilizumab on FXIII, thrombin generation and inflammation in patients with RA na\uefve for the drug. Methods: We studied 15 consecutive adult patients with RA at baseline and 4 weeks after the onset of parenteral administration of tocilizumab, measuring disease activity and plasma levels of C-reactive protein (CRP), FXIII, and prothrombin fragments F1+2 by immunoenzymatic methods. Fifteen healthy subjects, sex-and age-matched with patients, served as normal controls for laboratory measurements. Results: At baseline, patients with established RA had a median DAS28 of 4.8 (3.2\u20138.3) and, compared to healthy controls, had higher plasma levels of CRP (p < 0.0001), FXIII (p = 0.017) and F1+2 (p < 0.0001). Four weeks after starting treatment with tocilizumab, based on the EULAR response criteria, eight patients were classifiable as responders and seven as non-responders. In responders, we observed a statistically significant reduction not only of the values of DAS28 and CRP (p = 0.012 for both), ut also of plasma levels of FXIII (p = 0.05) and F1+2 (p = 0.025). In non-responders, all the studied parameters were unchanged. Conclusion: The decrease of FXIII and F1+2 levels after tocilizumab treatment observed only in those patients who responded to the drug indicates that the effect of tocilizumab on the prothrombotic state is linked to the control of inflammation and disease activity and not to a direct effect of the drug, thus contributing to the reduction of the cardiovascular risk

Long-term thermal stability of high-efficiency polymer solar cells based on photocrosslinkable donor-acceptor conjugated polymers

Highly efficient polymer solar cells based on novel photocrosslinkable donor–acceptor conjugated polymers are fabricated and their long-term thermal stability is reported. After 72 h of thermal annealing at 150 °C, a stable power conversion efficiency as high as 4.7% is maintained. The control of active layer morphology and device performance through annealing is correlated with the synthetic design of the photocrosslinkable polymer

Thermoresponsive Host Polymer Matrix for Self-Healing Luminescent Solar Concentrators

© 2019 American Chemical Society. Luminescent solar concentrators (LSCs) are a promising solar energy technology for reducing architectural barriers to the integration of photovoltaic systems into the built environment. In this work, the first demonstration of thin-film LSCs based on a thermally reversible cross-linked host polymer is presented. This smart material is obtained via a dynamic-chemistry approach based on the Diels-Alder (DA) reaction between a furan-functionalized acrylic copolymer and an aliphatic bismaleimide to obtain optically clear, cross-linked systems capable of healing mechanical damage upon heat treatment. By carefully tuning the concentration of a perylene-based luminophore dopant, an optical efficiency as high as 4.9% can be achieved with this DA-based LSC. In addition, full recovery of device efficiency is demonstrated after complete thermal healing of mechanically induced surface damages as a result of the embedded DA functionality. The approach presented here paves the way to the development of highly efficient multifunctional thermoresponsive smart LSC systems.European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 818762

Development of a One-Dimensional Model for the Prediction of Leakage Flows in Regenerative Pumps

Regenerative pumps are characterized by a low specific speed that place them between rotary positive displacement pumps and purely radial centrifugal pumps. They are interesting for many industrial applications since, for a given flow rate and a specified head, they allow for a reduced size and can operate at a lower rotational speed with respect to purely radial pumps. The complexity of the flow within regenerative machines makes the theoretical performance estimation a challenging task. The prediction of the leakage flow rate between the rotating and the static disks is the one that more than others has an impact on the prediction of global performance. All the classical approaches to the disk clearance problem assume that there is no relevant circumferential pressure gradient. In the present case, the flow develops along the tangential direction and the pressure gradient is intrinsically non-zero. The aim of the present work is to develop a reliable approach for the prediction of leakage flows in regenerative pumps. The method assumes that the flow inside of the disk clearance can be decomposed into several stream-tubes. Energy balance is performed for each tube, thus generating a system that can be solved numerically. The new methodology has been tuned using data obtained from the numerical simulation of virtual prototypes of regenerative pumps where the disk clearance is part of the control volume. After that, the methodology has been integrated into an existing one-dimensional code called DART (developed at the University of Florence in cooperation with Pierburg Pump Technology Italy S.p.A.) and the new algorithm is verified using available experimental and numerical data. It is here demonstrated that an appropriate calibration of the leakage flow model allows for an improved reliability of the one-dimensional code

Perylenetetracarboxy-3,4:9,10-diimide derivatives with large two-photon absorption activity

Three new perylenetetracarboxy-3,4:9,10-diimides, bearing 2,6-diisopropylphenyl groups at the imide positions and 4-(R-ethynyl)phenoxy moieties (R = 4,7-di(2-thienyl)benzo[c][1,2,5]thiadiazole (P2), pyrene (P3) or pyrene-CH2OCH2 (P4)) at the four bay positions, were prepared, along with the known related derivative (R = phenyl (P1)), and well characterized. They have large two-photon absorption (TPA) cross-sections (sigma(2)), as determined by the Z-scan technique, the highest values being reached with P2 which bears a planar -delocalized donor moiety. P3 is characterized by higher sigma(2) values than both P1, as expected for the higher -conjugation of the donor pyrene moiety with respect to phenyl, and P4, due to the presence of the flexible and non-conjugated CH2OCH2 bridge between the pyrene and the ethynyl fragment in the latter compound. The molecular geometry of P1-P4 has been optimized by DFT modeling, showing that in P2 and P3 the bay substituents are stacked due to the - interactions of both pyrene and thiophene groups. The LUMO of P1-P4 lies at the same energy and is essentially delocalized on the perylene core whereas the HOMO and HOMO-1 of both P2 and P3 are degenerate and do not show contribution from the perylene core contrarily to that of P1 and P4. The HOMO-LUMO gap is therefore essentially influenced by the HOMO which reflects the electronic charge delocalization on the bay substituents, the lower gaps being observed for P2 and P3, which are characterized by the best TPA properties

Cardanol-Derived Epoxy Resins as Biobased Gel Polymer Electrolytes for Potassium-Ion Conduction

In this study, biobased gel polymer electrolyte (GPE) membranes were developed via the esterification reaction of a cardanol-based epoxy resin with glutaric anhydride, succinic anhydride, and hexahydro-4-methylphthalic anhydride. Nonisothermal differential scanning calorimetry was used to assess the optimal curing time and temperature of the formulations, evidencing a process activation energy of ∼65–70 kJ mol–1. A rubbery plateau modulus of 0.65–0.78 MPa and a crosslinking density of 2 × 10–4 mol cm–3 were found through dynamic mechanical analysis. Based on these characteristics, such biobased membranes were tested for applicability as GPEs for potassium-ion batteries (KIBs), showing an excellent electrochemical stability toward potassium metal in the −0.2–5 V voltage range and suitable ionic conductivity (10–3 S cm–1) at room temperature. This study demonstrates the practical viability of these biobased materials as efficient GPEs for the fabrication of KIBs, paving the path to increased sustainability in the field of next-generation battery technologies

Lignin as polymer electrolyte precursor for stable and sustainable potassium batteries

Potassium batteries show interesting peculiarities as large-scale energy storage systems and, in this scenario, the formulation of polymer electrolytes obtained from sustainable resources or waste-derived products represents a milestone activity. In this study, a lignin-based membrane is designed by crosslinking a pre-oxidized Kraft lignin matrix with an ethoxylated difunctional oligomer, leading to self-standing membranes that are able to incorporate solvated potassium salts. The in-depth electrochemical characterization highlights a wide stability window (up to 4 V) and an ionic conductivity exceeding 10−3 S cm−1 at ambient temperature. When potassium metal cell prototypes are assembled, the lignin-based electrolyte attains significant electrochemical performances, with an initial specific capacity of 168 mAh g−1 at 0.05 A g−1 and an excellent operation for more than 200 cycles, which is an unprecedented outcome for biosourced systems in potassium batteries