Use of a sol-gel hybrid coating composed by a fluoropolymer and silica for the mitigation of mineral fouling in heat exchangers

The technology of the organic/inorganic hybrid coating was employed in the preparation of a hydrophobic coating (contact angle higher than 140\ub0) for fouling mitigation on stainless steel heat transfer surfaces. A commercial triethoxysilane perfluoropolyethers was combined with a sol-gel silica network with the aim to increase the mechanical and thermal resistance of the films when exposed to aggressive liquid environments as the heat exchanging fluids. The experimentation on a shell and tube heat exchanger pilot plant confirmed the ability of the hybrid coating to prolong the crystallization fouling induction period of 200 h in respect to an uncoated heat exchanger, operating in the same conditions. Moreover, the fouling particles deposited on the coated heat transfer surfaces had only slight adhesion strength toward the coated surfaces and were easily removed by inducing higher wall shear stresses inside the tubes of the plant

Cambios estacionales de la densidad de peces en una laguna del valle aluvial del rio Parana (Argentina)

En aval du confluent du Parana et du Paraguay, les nombreuses espèces de poissons présentes (dont beaucoup d'intérêt commercial) accomplissent des migrations complexes, latérales et longitudinales, encore inexpliquées. La structure et la densité des communautés de poissons sont fonction, pour chaque endroit, de la période de l'année. Ces variations ont été relevées dans une mare permanente de 274,5 ha dans la zone centrale de la plaine d'inondation (31°42'S; 60°37'W), et reliées à la température et au niveau de l'eau. Des estimations mensuelles de densité ont été faites entre janvier 1982 et janvier 1983 par écho-sondage, ainsi que par des pêches expérimentales utilisant les mêmes filets maillants que ceux des pêcheurs locaux. La prise moyenne a été de 21,5 kg par jour pour 100 m2 de file

Perfluoropolyethers coatings design for fouling reduction on heat transfer stainless steel surfaces

The scope of this research is to obtain a film coating on stainless steel surfaces in order to reduce the interaction between the metal surface and the precipitates, so to mitigate fouling in heat exchangers. Perfuoropolyethers were used to obtain nano-range fluorinated layers in order to make hydrophobic the stainless steel surfaces. A pilot plant with two identical heat exchangers was built to investigate the ability of the hydrophobic coating of preventing fouling. The heat exchangers, installed in parallel, operated at the same temperature and pressure conditions, i.e. laminar flow regime and inlet flow temperatures of 291\u2013293 K for cold streams and 313\u2013333 K for hot streams. We compared the heat transfer performance of the two heat exchangers. After a five months operation the decrease in the heat transferred was 56% for the coated heat exchanger and 62% for the uncoated heat exchanger. Moreover, the increase of heat transfer resistance due to scale on the uncoated heat exchanger, with respect to the coated one, was three times higher

Neurometabolic changes in a rat pup model of type C hepatic encephalopathy depend on age at liver disease onset.

Chronic liver disease (CLD) is a serious condition where various toxins present in the blood affect the brain leading to type C hepatic encephalopathy (HE). Both adults and children are impacted, while children may display unique vulnerabilities depending on the affected window of brain development.We aimed to use the advantages of high field proton Magnetic Resonance Spectroscopy ( <sup>1</sup> H MRS) to study longitudinally the neurometabolic and behavioural effects of Bile Duct Ligation (animal model of CLD-induced type C HE) on rats at post-natal day 15 (p15) to get closer to neonatal onset liver disease. Furthermore, we compared two sets of animals (p15 and p21-previously published) to evaluate whether the brain responds differently to CLD according to age onset.We showed for the first time that when CLD was acquired at p15, the rats presented the typical signs of CLD, i.e. rise in plasma bilirubin and ammonium, and developed the characteristic brain metabolic changes associated with type C HE (e.g. glutamine increase and osmolytes decrease). When compared to rats that acquired CLD at p21, p15 rats did not show any significant difference in plasma biochemistry, but displayed a delayed increase in brain glutamine and decrease in total-choline. The changes in neurotransmitters were milder than in p21 rats. Moreover, p15 rats showed an earlier increase in brain lactate and a different antioxidant response. These findings offer tentative pointers as to which neurodevelopmental processes may be impacted and raise the question of whether similar changes might exist in humans but are missed owing to <sup>1</sup> H MRS methodological limitations in field strength of clinical magnet

Experiencia en la fabricación de titanio con gradiente de porosidad mediante técnicas de pulvimetalurgia

Fil: Grinschpun, L. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Materiales; Argentina.Fil: Oldani, C. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Materiales; Argentina.Fil: Valdemarin, M. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Materiales; Argentina.El titanio se reconoce como el mejor material metálico para reemplazo óseo. Este consenso está basado en sus buenas propiedades mecánicas, adecuadas para aplicaciones donde se deban soportar cargas (módulo elástico de 100-110 GPa y resistencia a la tracción entre 240-550 MPa) [1], su muy buena resistencia a la corrosión y su excelente respuesta in vivo debido a su capacidad osteoinductiva y osteointegradora. A pesar de esto, el titanio presenta algunos inconvenientes ya que es un material bioinerte (no reacciona adversamente con el tejido) y estable químicamente (resistencia a la corrosión excelente, especialmente frente a los ambientes fisiológicos) y en consecuencia, el organismo tiende a formar una cápsula de tejido fibroso a su alrededor comprometiendo la osteointegración del implante (capacidad de establecer una conexión directa, estructural y funcional, entre el hueso y la superficie del implante). Los posibles micromovimientos que ocurren en la intercara biomaterial-tejido, generan a mediano y largo plazo, un crecimiento de la fina capa de tejido fibroso ya existente, incrementándose el riesgo de aflojamiento del implante.Fil: Grinschpun, L. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Materiales; Argentina.Fil: Oldani, C. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Materiales; Argentina.Fil: Valdemarin, M. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Materiales; Argentina.Ingeniería de los Materiale

Experiencias en la fabricación de titanio con gradiente de porosidad mediante técnicas de pulvimetalurgia

Fil: Grinschpun, L. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Materiales; Argentina.Fil: Oldani, C. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Materiales; Argentina.Fil: Valdemarin, M. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Materiales; Argentina.Titanium is recognized as the best biometal for applications in bone implant.However it presents some difficulties as is the mismatch between its modulus of elasticity(stiffness) and that of the bone that replace. This difference produce stress-shielding, aphenomenon by which bone is retracted, weakens and can suffer a new fracture. One possiblesolution is to decrease the stiffness by obtaining a porous structure with controlled porosity innumber, size and shape of the pores. The presence of different tissues in contact with theimplant makes ideal to have a titanium metal structure with porosity gradients. A suitabletechnique for obtaining this structure is powder metallurgy (PM). This paper use PMtechniques with TiH2 as the titanium source and ammonium bicarbonate as pore spacerparticles, sintered at 1000 ° C in argon atmosphere. There were obtained samples withlongitudinal and radial porosity gradient. The main drawbacks are found in matrix fillingtechniques for compact the greens. This causes joints between layers with different porositynot adequate and separated by differential shrinkage during the sintering treatment. Despitethis, optimization of the treatment conditions enables the samples obtained present very goodadhesion between layers.Fil: Grinschpun, L. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Materiales; Argentina.Fil: Oldani, C. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Materiales; Argentina.Fil: Valdemarin, M. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Materiales; Argentina.Ingeniería de los Materiale

SynaptoPAC, an optogenetic tool for induction of presynaptic plasticity

Optogenetic manipulations have transformed neuroscience in recent years. While sophisticated tools now exist for controlling the firing patterns of neurons, it remains challenging to optogenetically define the plasticity state of individual synapses. A variety of synapses in the mammalian brain express presynaptic long-term potentiation (LTP) upon elevation of presynaptic cyclic adenosine monophosphate (cAMP), but the molecular expression mechanisms as well as the impact of presynaptic LTP on network activity and behavior are not fully understood. In order to establish optogenetic control of presynaptic cAMP levels and thereby presynaptic potentiation, we developed synaptoPAC, a presynaptically targeted version of the photoactivated adenylyl cyclase bPAC. In cultures of hippocampal granule cells, activation of synaptoPAC with blue light increases action potential-evoked transmission, an effect not seen in hippocampal cultures of non-granule cells. In acute brain slices, synaptoPAC activation immediately triggers a strong presynaptic potentiation at mossy fiber terminals in CA3, but not at Schaffer collateral synapse in CA1. Following light-triggered potentiation, mossy fiber transmission decreases within 20 minutes, but remains enhanced still after 30 min. Optogenetic potentiation alters the short-term plasticity dynamics of release, reminiscent of presynaptic LTP. SynaptoPAC is the first optogenetic tool that allows acute light-controlled potentiation of transmitter release at specific synapses of the brain, and will enable to investigate the role of presynaptic potentiation in network function and the animal’s behavior in an unprecedented manner. SIGNIFICANCE STATEMENT: SynaptoPAC is a novel optogenetic tool that allows increasing synaptic transmission by light-controlled induction of presynaptic plasticity

Reinforcement of perfluoropolyethers coatings by ceramic oxides sol-gels for fouling mitigation on metal surfaces

In this research we developed a coating formulation containing \u3b1,\u3c9-substituted perfluoropolyethers (PFPE) and ceramic oxides sol-gels, for fouling mitigation on solid surfaces. Micrometer coatings where obtained on metal substrates by dip-coating procedure; they showed hydrophobic behavior (CA>130\ub0) and low CA hysteresis. The coatings resistance against shear stresses and chemicals increased thanks to the high mechanical properties of the ceramic oxides, compared to a simple PFPE coating. The ability of the coatings to mitigate particulate fouling was preliminary confirmed in presence of CaSO4 in an appropriate test rig. Motivations and Objectives One potential application of hydrophobic coatings concerns fouling mitigation. It has been demonstrated that low energy surfaces are able to influence the mechanism of deposition and removal of fouling particles on heat transfer surfaces, increasing the fouling induction period of the heat exchangers [1]. This research aims to develop a hydrophobic organic-inorganic coating, combining a PFPE with a sol-gel network obtained from the hydrolysis of tetraethylorthosilicate (OTES) or Zr-n-propoxide, in order to improve the mechanical properties of the final coatings. The investigation focuses the attention on the important coatings parameters for a possible application on heat transfer surfaces, i.e., thickness, thermal resistance, surface roughness and chemical and physical resistance. Fouling mitigation ability of the coatings is assessed in particulate fouling conditions, in a specific test rig. Hydrophobic coatings were obtained by formulating in iso-propanol a commercial PFPE (Fluorolink\uaeS10) with SiO2 or ZrO2 sol-gels, at different weight proportion (80/20, 1/05 and 1/1 respectively). The coatings resistance was investigated against erosion induced by liquid environments and shear stresses induced by a water flow. Compared to a simple PFPE coating, the resistance against shear stresses and aggressive environments increased of the 90%. Fouling mitigation ability of coatings deposited on the internal surfaces of a stainless steel tube, was assessed in presence of a CaSO4 solution (4 g/L), flowed inside a coated tube (temperature=40\ub0C, flowrate= 1.5 m/s). Thanks to the hydrophobic coating, the foulants deposition is 95% lower in respect to an uncoated surface

Aquivion® PFSA-based spray-freeze dried composite materials with SiO2 and TiO2 as hybrid catalysts for the gas phase dehydration of ethanol to ethylene in mild conditions

Aquivion PFSA resin, a perfluorinated ion-exchange polymer, has been used as a heterogeneous strong acid catalyst for a range of reactions; however, the activity of this material is limited due to the extremely low surface area of the polymer. In this paper we described the one-step synthesis of Aquivion® PFSA-based hybrid materials using heterocoagulation and spray-freeze-drying of sols containing the precursor of the active phases. The intimated encapsulation of different nano-oxides, such as TiO2 and SiO2 in the superacid resin matrix was easily obtained using this technique and compared with similar catalysts prepared by the impregnation conventional route. The approach led to the preparation of porous micro-granules characterised by a high homogeneity in the phase distribution and high surface area. The prepared materials were active and selective for the gas phase dehydration of ethanol to ethylene in mild conditions. The increase of the porosity improved the activity of the composites, compared to the pure Aquivion® PFSA, and allowed to reduce the amount of the superacid resin. Moreover, the type of encapsulated oxide, TiO2 or SiO2, modified the improved performance of the catalysts, having TiO2 the higher efficiency for ethanol conversion and selectivity in ethylene at very low temperature