Mixing in convective thermal fluxes in unsteady nonhomogeneous flows generating complex three dimensional vorticity patterns

Diffusion and scaling of the velocity and vorticity in a thermoelectric driven heating and cooling experimental device is presented in order to map the different patterns and transitions between two and three dimensional convection in an enclosure with complex driven flows. The size of the water tank is of 0.2 x 0.2 x 0.1 m and the heat sources or sinks can be regulated both in power and sign [1-3]. The thermal convective driven flows are generated by means of Peltier effects in 4 wall extended positions of 0.05 x 0.05 cm each. The parameter range of convective cell array varies strongly with the Topology of the boundary conditions. Side heat and momentum fluxes are a function of Rayleigh, Peclet and Nusselt numbers, [4-6] Visualizations are performed by PIV, Particle tracking and shadowgraph. The structure of the flow is shown by setting up a convective flow generated by buoyant heat fluxes. The experiments described here investigate high Prandtl number mixing using brine and fresh water in order to form a density interface and low Prandtl number mixing with temperature gradients. The evolution of the mixing fronts are compared and the topological characteristics of the merging of the convective structures are examined for different configurations. Based on two dimensional Vorticity spectral analysis, new techniques can be very useful to determine the evolution of scales considering the multi-fractal structure of the convective flows.Peer ReviewedPostprint (published version

Fermi surface renormalization in Hubbard ladders

We derive the one-loop renormalization equations for the shift in the Fermi-wavevectors for one-dimensional interacting models with four Fermi-points (two left and two right movers) and two Fermi velocities v_1 and v_2. We find the shift to be proportional to (v_1-v_2)U^2, where U is the Hubbard-U. Our results apply to the Hubbard ladder and to the t_1-t_2 Hubbard model. The Fermi-sea with fewer particles tends to empty. The stability of a saddle point due to shifts of the Fermi-energy and the shift of the Fermi-wavevector at the Mott-Hubbard transition are discussed.Comment: 5 pages, 4 Postscript figure

Monitoring of evoked potentials during spinal cord ischaemia: Experimental evaluation in a rabbit model

Objectives:somatosensory evoked potentials (SEPs), spinal evoked potentials (Spinal-EPs), and motor-evoked potentials (MEPs) were monitored in a rabbit model of spinal cord ischaemia to evaluate their accuracy and relationship to clinical status.Methods:a modified rabbit spinal cord ischaemia model of infrarenal aortic occlusion for 21 min was employed (30 rabbits). After baseline SEPs, Spinal-EPs, and MEPs were obtained, evoked potentials were recorded continuously during and after clamping of the aorta (30 min). Neurological outcome at 24 h was correlated with evoked potentials, and histopathological findings.Results:fifteen animals became paraplegic. MEPs were always abolished after clamping of the aorta while Spinal-EPs and SEPs remained. The sensory evoked potentials (SEPs and Spinal-EPs) were the least sensitive to spinal cord ischaemia, and their presence had no correlation with the final clinical status (50% of false negatives). This was consistent with histopathological examination that showed damage almost entirely confined to the anterior horn, while the dorsal columns were generally well preserved. High spine MEPs evoked by twitch stimulation was the best predictor of clinical outcome (0% of false negatives, 0% of false positives).Conclusions:SEPs and Spinal-EPs cannot be used as safe monitors of ischaemia of the spinal cord. High spine MEPs evoked by twitch stimulation was the most useful for real-time evaluation of spinal cord ischaemia, and the best predictor of neurologic outcome during reperfusion

Long-Circulating Hyaluronan-Based Nanohydrogels as Carriers of Hydrophobic Drugs

[EN] Nanohydrogels based on natural polymers, such as polysaccharides, are gaining interest as vehicles for therapeutic agents, as they can modify the pharmacokinetics and pharmacodynamics of the carried drugs. In this work, hyaluronan-riboflavin nanohydrogels were tested in vivo in healthy rats highlighting their lack of toxicity, even at high doses, and their different biodistribution with respect to that of native hyaluronan. They were also exploited as carriers of a hydrophobic model drug, the anti-inflammatory piroxicam, that was physically embedded within the nanohydrogels by an autoclave treatment. The nanoformulation was tested by intravenous administration showing an improvement of the pharmacokinetic parameters of the molecule. The obtained results indicate that hyaluronan-based self-assembled nanohydrogels are suitable systems for low-soluble drug administration, by increasing the dose as well as the circulation time of poorly available therapeutic agents.Financial support from University Sapienza Progetti di Ricerca: grant RP116154C2EF9AC8 and grant RM11715C1743EE89 are acknowledged. Isabel Gonzalez-Alvarez, Marta Gonzalez-Alvarez and Marival Bermejo acknowledge partial financial support to project SAF2016-78756 from MINECO (Spanish Ministry of economy, industry and competitivity). Mayte Martinez-Martínez received a grant from the Ministry of Education and Science of Spain (FPU13-01105).Di Meo, C.; Martínez Martínez, M.; Coviello, T.; Bermejo, M.; Merino Sanjuán, V.; Gonzalez-Alvarez, I.; Gonzalez-Alvarez, M.... (2018). Long-Circulating Hyaluronan-Based Nanohydrogels as Carriers of Hydrophobic Drugs. Pharmaceutics. 10(4):1-15. https://doi.org/10.3390/pharmaceutics10040213S115104Allison, D. D., & Grande-Allen, K. J. (2006). Review. Hyaluronan: A Powerful Tissue Engineering Tool. Tissue Engineering, 12(8), 2131-2140. doi:10.1089/ten.2006.12.2131Prestwich, G. D. (2008). Engineering a clinically-useful matrix for cell therapy. Organogenesis, 4(1), 42-47. doi:10.4161/org.6152Ossipov, D. A. (2010). Nanostructured hyaluronic acid-based materials for active delivery to cancer. Expert Opinion on Drug Delivery, 7(6), 681-703. doi:10.1517/17425241003730399Rao, N. V., Yoon, H. Y., Han, H. S., Ko, H., Son, S., Lee, M., … Park, J. H. (2015). Recent developments in hyaluronic acid-based nanomedicine for targeted cancer treatment. Expert Opinion on Drug Delivery, 13(2), 239-252. doi:10.1517/17425247.2016.1112374Dosio, F., Arpicco, S., Stella, B., & Fattal, E. (2016). Hyaluronic acid for anticancer drug and nucleic acid delivery. Advanced Drug Delivery Reviews, 97, 204-236. doi:10.1016/j.addr.2015.11.011Montanari, E., D’Arrigo, G., Di Meo, C., Virga, A., Coviello, T., Passariello, C., & Matricardi, P. (2014). Chasing bacteria within the cells using levofloxacin-loaded hyaluronic acid nanohydrogels. European Journal of Pharmaceutics and Biopharmaceutics, 87(3), 518-523. doi:10.1016/j.ejpb.2014.03.003Svanovsky, E., Velebny, V., Laznickova, A., & Laznicek, M. (2008). The effect of molecular weight on the biodistribution of hyaluronic acid radiolabeled with111In after intravenous administration to rats. European Journal of Drug Metabolism and Pharmacokinetics, 33(3), 149-157. doi:10.1007/bf03191112Harris, E. N., Kyosseva, S. V., Weigel, J. A., & Weigel, P. H. (2006). Expression, Processing, and Glycosaminoglycan Binding Activity of the Recombinant Human 315-kDa Hyaluronic Acid Receptor for Endocytosis (HARE). Journal of Biological Chemistry, 282(5), 2785-2797. doi:10.1074/jbc.m607787200Choi, K. Y., Min, K. H., Na, J. H., Choi, K., Kim, K., Park, J. H., … Jeong, S. Y. (2009). Self-assembled hyaluronic acid nanoparticles as a potential drug carrier for cancer therapy: synthesis, characterization, and in vivo biodistribution. Journal of Materials Chemistry, 19(24), 4102. doi:10.1039/b900456dPedrosa, S. S., Pereira, P., Correia, A., & Gama, F. M. (2017). Targetability of hyaluronic acid nanogel to cancer cells : In vitro and in vivo studies. European Journal of Pharmaceutical Sciences, 104, 102-113. doi:10.1016/j.ejps.2017.03.045Yang, C., Li, C., Zhang, P., Wu, W., & Jiang, X. (2017). Redox Responsive Hyaluronic Acid Nanogels for Treating RHAMM (CD168) Over-expressive Cancer, both Primary and Metastatic Tumors. Theranostics, 7(6), 1719-1734. doi:10.7150/thno.18340Rosso, F., Quagliariello, V., Tortora, C., Di Lazzaro, A., Barbarisi, A., & Iaffaioli, R. V. (2013). Cross-linked hyaluronic acid sub-micron particles: in vitro and in vivo biodistribution study in cancer xenograft model. Journal of Materials Science: Materials in Medicine, 24(6), 1473-1481. doi:10.1007/s10856-013-4895-4Nakai, T., Hirakura, T., Sakurai, Y., Shimoboji, T., Ishigai, M., & Akiyoshi, K. (2012). Injectable Hydrogel for Sustained Protein Release by Salt-Induced Association of Hyaluronic Acid Nanogel. Macromolecular Bioscience, 12(4), 475-483. doi:10.1002/mabi.201100352Montanari, E., Capece, S., Di Meo, C., Meringolo, M., Coviello, T., Agostinelli, E., & Matricardi, P. (2013). Hyaluronic Acid Nanohydrogels as a Useful Tool for BSAO Immobilization in the Treatment of Melanoma Cancer Cells. Macromolecular Bioscience, 13(9), 1185-1194. doi:10.1002/mabi.201300114Montanari, E., Di Meo, C., Sennato, S., Francioso, A., Marinelli, A. L., Ranzo, F., … Matricardi, P. (2017). Hyaluronan-cholesterol nanohydrogels: Characterisation and effectiveness in carrying alginate lyase. New Biotechnology, 37, 80-89. doi:10.1016/j.nbt.2016.08.004Montanari, E., De Rugeriis, M. C., Di Meo, C., Censi, R., Coviello, T., Alhaique, F., & Matricardi, P. (2015). One-step formation and sterilization of gellan and hyaluronan nanohydrogels using autoclave. Journal of Materials Science: Materials in Medicine, 26(1). doi:10.1007/s10856-014-5362-6Di Meo, C., Montanari, E., Manzi, L., Villani, C., Coviello, T., & Matricardi, P. (2015). Highly versatile nanohydrogel platform based on riboflavin-polysaccharide derivatives useful in the development of intrinsically fluorescent and cytocompatible drug carriers. Carbohydrate Polymers, 115, 502-509. doi:10.1016/j.carbpol.2014.08.107Manzi, G., Zoratto, N., Matano, S., Sabia, R., Villani, C., Coviello, T., … Di Meo, C. (2017). «Click» hyaluronan based nanohydrogels as multifunctionalizable carriers for hydrophobic drugs. Carbohydrate Polymers, 174, 706-715. doi:10.1016/j.carbpol.2017.07.003Lozoya-Agullo, I., Araújo, F., González-Álvarez, I., Merino-Sanjuán, M., González-Álvarez, M., Bermejo, M., & Sarmento, B. (2018). PLGA nanoparticles are effective to control the colonic release and absorption on ibuprofen. European Journal of Pharmaceutical Sciences, 115, 119-125. doi:10.1016/j.ejps.2017.12.009Samiei, N., Mangas-Sanjuan, V., González-Álvarez, I., Foroutan, M., Shafaati, A., Zarghi, A., & Bermejo, M. (2013). Ion-pair strategy for enabling amifostine oral absorption: Rat in situ and in vivo experiments. European Journal of Pharmaceutical Sciences, 49(4), 499-504. doi:10.1016/j.ejps.2013.04.025Wei, X., Senanayake, T. H., Bohling, A., & Vinogradov, S. V. (2014). Targeted Nanogel Conjugate for Improved Stability and Cellular Permeability of Curcumin: Synthesis, Pharmacokinetics, and Tumor Growth Inhibition. Molecular Pharmaceutics, 11(9), 3112-3122. doi:10.1021/mp500290

The role of spatial and temporal radiation deposition in inertial fusion chambers: the case of HiPER¿

The first wall armour for the reactor chamber of HiPER will have to face short energy pulses of 5 to 20 MJ mostly in the form of x-rays and charged particles at a repetition rate of 5–10 Hz. Armour material and chamber dimensions have to be chosen to avoid/minimize damage to the chamber, ensuring the proper functioning of the facility during its planned lifetime. The maximum energy fluence that the armour can withstand without risk of failure, is determined by temporal and spatial deposition of the radiation energy inside the material. In this paper, simulations on the thermal effect of the radiation–armour interaction are carried out with an increasing definition of the temporal and spatial deposition of energy to prove their influence on the final results. These calculations will lead us to present the first values of the thermo-mechanical behaviour of the tungsten armour designed for the HiPER project under a shock ignition target of 48 MJ. The results will show that only the crossing of the plasticity limit in the first few micrometres might be a threat after thousands of shots for the survivability of the armour