Numerical simulation of the gas–liquid flow in a laboratory scale bubble column: Influence of bubble size distribution and non-drag forces

In the present work, a computational model based on an Eulerian–Eulerian approach was used for the simulation of the transient two-phase flow in a rectangular partially aerated bubble column. Superficial gas velocities (U_G) ranging from 0.24 to 2.30 cm/s were used throughout both the experiments and the simulations. The calculated results were verified by comparing them with experimental data including measurements of gas hold-up, plume oscillation period (POP) and Sauter mean bubble diameter. The study shows the effect of mesh refinement, time-step and physical model selection, the latter regarding the role of bubble size distribution and non-drag forces, on the computational results. According to the results presented here, the representation of bubble populations using multiple size groups (MUSIG model) instead of a single group improves the prediction of the experimental parameters under study. Additionally, the results obtained after including the virtual mass force term do not differ considerably from those obtained including only the drag force. On the contrary, as a consequence of introducing the lift force term into the model, the gas hold-up is overestimated and a non-symmetric bubble plume oscillation appears, a fact that is not experimentally observed.     

Development of nanostructured catalytic membranes for partial benzene hydrogenation to cyclohexene

Novel nanostructured catalytic membranes (NCMs) have been prepared by ruthenium deposition (Ru3(CO)12 wet-impregnation) within the porous framework of different tubular porous supports modified and unmodified with microporous glassy-carbon (GC) material. The aim of this work is to investigate the influence of the transport mechanism, layer distribution, textural properties, surface composition and metallic phase distribution of each type of NCMs on the partial benzene hydrogenation to cyclohexene performance in gas phase, operating under through-flow mode in a membrane reactor. Two types of glass (Vycor) and ceramic (Cordierite-Alumina) supports with different layer distribution, have been used to prepared the NCMs. The modified and unmodified with GC membranes have been characterised by gas permeability measurements. High resolution-scanning electron microscopy (HR-SEM) and energy dispersive X-ray spectroscopy (EDS) have been realised to evidence GC deposition and to analyse the ruthenium nanoparticles distribution along the porous membranes section, respectively. An attempt to correlate the membrane characterization results and the catalytic results has been carried out.     

Heparin Modulates the Mitogenic Activity of Fibroblast Growth Factor by Inducing Dimerization of its Receptor. A 3D View by Using NMR

In vitro mitogenesis assays have shown that sulfated glycosaminoglycans (GAGs; heparin and heparan sulfate) cause an enhancement of the mitogenic activity of fibroblast growth factors (FGFs). Herein, we report that the simultaneous presence of FGF and the GAG is not an essential requisite for this event to take place. Indeed, preincubation with heparin (just before FGF addition) of cells lacking heparan sulfate produced an enhancing effect equivalent to that observed when the GAG and the protein are simultaneously added. A first structural characterization of this effect by analytical ultracentrifugation of a soluble preparation of the heparin‐binding domain of fibroblast growth factor receptor 2 (FGFR2) and a low molecular weight (3 kDa) heparin showed that the GAG induces dimerization of FGFR2. To derive a high resolution structural picture of this molecular recognition process, the interactions of a soluble heparin‐binding domain of FGFR2 with two different homogeneous, synthetic, and mitogenically active sulfated GAGs were analyzed by NMR spectroscopy. These studies, assisted by docking protocols and molecular dynamics simulations, have demonstrated that the interactions of these GAGs with the soluble heparin‐binding domain of FGFR induces formation of an FGFR dimer; its architecture is equivalent to that in one of the two distinct crystallographic structures of FGFR in complex with both heparin and FGF1. This preformation of the FGFR dimer (with similar topology to that of the signaling complex) should favor incorporation of the FGF component to form the final assemblage of the signaling complex, without major entropy penalty. This cascade of events is probably at the heart of the observed activating effect of heparin in FGF‐driven mitogenesis.     

The effect of oil raw material composition in the synthesis of bio-sorbents based on inverse vulcanization on the ability to remediate hydrocarbon-contaminated water. A novel method for decontaminating water/fuel emulsions

Solid crosslinked biopolymers made by inverse vulcanization of soybean (PSB) or sunflower (PSF) oil with sulfur are characterized and tested to decontaminate water from hydrocarbons (HC): gasoline, diesel, two lubricant oils, and water/gasoline emulsion. The physicochemical structure of the biopolymers is studied by FTIR spectroscopy, Differential scanning calorimetry, contact angle measurement, and mechanical testing. Also, the morphological structure is analyzed by scanning electron microscopy. Moreover, the polymer decontamination capability and reusability are tested gravimetrically. Both biopolymers are formed by C S bonds, and their elastic behavior dominates. However, PSF is more hydrophilic, has a larger amount of free sulfur and a less compact structure, and also sorbs ca. 60% more HC than PSB. The results indicate that the unsaturated feedstock has a strong effect on the polymer structure and the capacity to remediate contaminated water or solids. Also, both materials can be reused to remediate water for more than five consecutive cycles. In addition, inverse vulcanization of oils and sulfur is an ecological way of obtaining environmentally-improved materials with great potential and applications, providing a complete atomic economy and high performance to remediate water from water/HCs dispersed and, more importantly, from water/gasoline emulsions.     

Behavior of sandwich structures and spaced plates subjected to high‐velocity impacts

This work evaluates the behavior of sandwich and spaced plates subjected to high‐velocity impacts. The sandwich structures were made of glass/polyester face‐sheet and a PVC foam core. The spaced plates were made of two plates of the same material of the sandwich face‐sheet at a distance equal to the core thickness. The residual velocity, the ballistic limit, and the damage area were selected to compare the response of both structures. The residual velocity and ballistic limit was very similar in both cases. Nevertheless, the damage area of sandwich structures and spaced plates differed due to the dissimilar properties between the sandwich core and the air inside of the spaced plates. An analytical model, based on energy criteria, was applied to estimate the residual velocity of the projectile, the absorbed energy by each face‐sheet, and the ballistic limit in the spaced plates. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

Enzymatic Synthesis of α‐Glucosides of Resveratrol with Surfactant Activity

We report the synthesis of a series of α‐glucosyl derivatives of resveratrol (3,5,4′‐trihydroxystilbene) by a transglycosylation reaction catalyzed by the enzyme cyclodextrin glucanotransferase (CGTase) using starch as glucosyl donor. Several reaction parameters (temperature, solvent composition, enzyme concentration and starch/resveratrol ratio) were optimized. The yield of α‐glucosylated products reached 50% in 24 h. The structures of the derivatives were determined by a combination of amyloglucosidase‐hydrolysis tests, MS and 2D‐NMR. Three families of products were obtained: glucosylated at 3‐OH, at 4′‐OH and at both 3‐OH and 4′‐OH. The bonds between glucoses were basically α(1→4). Interestingly, the water solubilities of the α‐glucosylated derivatives were at least 65‐ and 5‐fold higher than those of resveratrol and the natural β‐glucosylated derivative (piceid), respectively. In contrast with piceid, the synthesized α‐glucosylated compounds exhibited surfactant activity, with critical micelle concentration (CMC) values in the range 0.5–3.6 mM. Although the incorporation of a glucosyl moiety caused a loss of antioxidant activity (more pronounced in the position 3‐OH compared with 4′‐OH), the fact that the glycosides need to be converted into the aglycones before they are absorbed minimizes such an effect. In contrast, the modification of physicochemical properties such as solubility and partition coefficient by glycosylation could exert a positive influence on the bioavailability of resveratrol.     

Modeling In Vitro Osteoarthritis Phenotypes in a Vascularized Bone Model Based on a Bone-Marrow Derived Mesenchymal Cell Line and Endothelial Cells

The subchondral bone and its associated vasculature play an important role in the onset of osteoarthritis (OA). Integration of different aspects of the OA environment into multi-cellular and complex human, in vitro models is therefore needed to properly represent the pathology. In this study, we exploited a mesenchymal stromal cell line/endothelial cell co-culture to produce an in vitro human model of vascularized osteogenic tissue. A cocktail of inflammatory cytokines, or conditioned medium from mechanically-induced OA engineered microcartilage, was administered to this vascularized bone model to mimic the inflamed OA environment, hypothesizing that these treatments could induce the onset of specific pathological traits. Exposure to the inflammatory factors led to increased network formation by endothelial cells, reminiscent of the abnormal angiogenesis found in OA subchondral bone, demineralization of the constructs, and increased collagen production, signs of OA related bone sclerosis. Furthermore, inflammation led to augmented expression of osteogenic (alkaline phosphatase (ALP) and osteocalcin (OCN)) and angiogenic (vascular endothelial growth factor (VEGF)) genes. The treatment, with a conditioned medium from the mechanically-induced OA engineered microcartilage, also caused increased demineralization and expression of ALP, OCN, ADAMTS5, and VEGF; however, changes in network formation by endothelial cells were not observed in this second case, suggesting a possible different mechanism of action in inducing OA-like phenotypes. We propose that this vascularized bone model could represent a first step for the in vitro study of bone changes under OA mimicking conditions and possibly serve as a tool in testing anti-OA drugs.     

Fast determination of capsaicinoids from peppers by high-performance liquid chromatography using a reversed phase monolithic column

This article reports the development of a rapid and reproducible method of HPLC with fluorescence detection for the determination and quantification of the main capsaicinoids (nordihydrocapsaicin, capsaicin, dihydrocapsaicin, homocapsaicin and homodihydro-capsaicin) present in hot peppers by employing a monolithic column. The type of column employed is a RP-18e (100 mm × 4.6 mm) monolithic column. A gradient method was utilised for the chromatographic separation: solvent A: water (0.1% acetic acid) and solvent B: methanol (0.1% acetic acid). A study was also made of the robustness of the method in respect of the conditions of temperature in the separation column (15–40 °C), the solvent flowrate (4–7 mL min⁻¹), the injection volume (10–50 μL), and the percentage of methanol in the sample (25–100%). The repeatability and reproducibility of the method showed relative standard deviations of less than 2%. The robustness of the method was determined by utilising different injection volumes and different percentages of methanol in the extracts. The method developed has then been utilised for the quantification of the major capsaicinoids present in different varieties of hot peppers grown in Spain. The capsaicinoids have been separated in a time of less than 8 min.     

Unraveling the Interaction between the LPS O‐Antigen of Burkholderia anthina and the 5D8 Monoclonal Antibody by Using a Multidisciplinary Chemical Approach,with Synthesis,NMR, and Molecular Modeling Methods

The interaction between the O‐chain from the lipopolysaccharide from Burkholderia anthina and a lipopolysaccharide‐specific monoclonal antibody (5D8) has been studied at high resolution by NMR spectroscopy. In particular, the 5D8‐bound epitope of the saccharide entity has been unraveled by a combination of saturation transfer difference (STD) and transferred NOESY (tr‐NOESY) experiments performed on the 5D8/polysaccharide complex. To dissect the fine details of the molecular recognition events, further experiments with simpler carbohydrate ligands were carried out. Thus, experiments were also performed with ad hoc synthesized trisaccharide and hexasaccharide O‐antigen repeating units. By using this multidisciplinary approach (chemical synthesis, NMR spectroscopy and molecular dynamics simulation), determination of the binding epitope and the contribution to the binding of the sugar units composing the O‐chain have been determined.