Densities and phase equilibria of hydrogen, propane and vegetable oil mixtures. Experimental data and thermodynamic modeling

Heterogeneous catalytic gas-liquid reactions are intensified when carried out in the homogenous fluid phase by means of a supercritical co-solvent. For instance, supercritical propane is used to enhance yield in the hydrogenation of vegetable oils. Besides phase equilibrium knowledge, volumetric information is also needed to elucidate kinetic mechanisms and design continuous supercritical reactors. In this work, we report new experimental PvT data of the reactive mixture H2+sunflower oil+propane using the isochoric method. In addition, the phase equilibria and PvT data are modeled with the GCA and RK-PR equations of state, respectively. The isochoric method not only provides PvT information under the reaction conditions, but also the reactive system compressibility, key variable to attain enhanced transport properties in the supercritical reactors.Fil: Hegel, Pablo Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Cotabarren, Natalia Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Brignole, Esteban Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Pereda, Selva. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. University of KwaZulu-Natal; Sudáfric

Interrogating Encapsulated Protein Structure within Metal–Organic Frameworks at Elevated Temperature

Encapsulating biomacromolecules within metal-organic frameworks (MOFs) can confer thermostability to entrapped guests. It has been hypothesized that the confinement of guest molecules within a rigid MOF scaffold results in heightened stability of the guests, but no direct evidence of this mechanism has been shown. Here, we present a novel analytical method using small-angle X-ray scattering (SAXS) to solve the structure of bovine serum albumin (BSA) while encapsulated within two zeolitic imidazolate frameworks (ZIF-67 and ZIF-8). Our approach comprises subtracting the scaled SAXS spectrum of the ZIF from that of the biocomposite BSA@ZIF to determine the radius of gyration of encapsulated BSA through Guinier, Kratky, and pair distance distribution function analyses. While native BSA exposed to 70 °C became denatured, in situ SAXS analysis showed that encapsulated BSA retained its size and folded state at 70 °C when encapsulated within a ZIF scaffold, suggesting that entrapment within MOF cavities inhibited protein unfolding and thus denaturation. This method of SAXS analysis not only provides insight into biomolecular stabilization in MOFs but may also offer a new approach to study the structure of other conformationally labile molecules in rigid matrices

Understanding the formation of deep eutectic solvents: betaine as a universal hydrogen bond acceptor

© 2020 Wiley-VCH GmbH The mechanism of formation of betaine-based deep eutectic solvents (DES) is presented for the first time. Due to its polarity unbalance, it was found that betaine displays strong negative deviations from ideality when mixed with a variety of different organic substances. These results pave the way for a comprehensive design of novel deep eutectic solvents. A connection to biologically relevant systems was made using betaine (osmolyte) and urea (protein denaturant), showing that these two compounds formed a DES, the molecular interactions of which were greatly enhanced in the presence of water.This work was developed within the scope of the projects CICECO-Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the Portuguese Foundation for Science and Technology/MCTES, and CIMO-Mountain Research Center, UIDB/00690/2020, financed by national funds through the FCT/MEC and when appropriate cofinanced by FEDER under the PT2020 Partnership Agreement.info:eu-repo/semantics/publishedVersio

Predicting phase equilibria in polydisperse systems

Many materials containing colloids or polymers are polydisperse: They comprise particles with properties (such as particle diameter, charge, or polymer chain length) that depend continuously on one or several parameters. This review focusses on the theoretical prediction of phase equilibria in polydisperse systems; the presence of an effectively infinite number of distinguishable particle species makes this a highly nontrivial task. I first describe qualitatively some of the novel features of polydisperse phase behaviour, and outline a theoretical framework within which they can be explored. Current techniques for predicting polydisperse phase equilibria are then reviewed. I also discuss applications to some simple model systems including homopolymers and random copolymers, spherical colloids and colloid-polymer mixtures, and liquid crystals formed from rod- and plate-like colloidal particles; the results surveyed give an idea of the rich phenomenology of polydisperse phase behaviour. Extensions to the study of polydispersity effects on interfacial behaviour and phase separation kinetics are outlined briefly.Comment: 48 pages, invited topical review for Journal of Physics: Condensed Matter; uses Institute of Physics style file iopart.cls (included

Gel meloksikama za topičku primjenu: In vitro i in vivo vrednovanje

Skin delivery of NSAIDs offers several advantages over the oral route associated with potential side effects. In the present investigation, topical gel of meloxicam (MLX) was formulated using N-methyl pyrrolidone (NMP) as a solubilizer and Carbopol Ultrez 10® as a gelling polymer. MLX gel was evaluated with respect to different physicochemical parameters such as pH, viscosity and spreadability. Irritation potential of MLX gel was studied on rabbits. Permeation of MLX gel was studied using freshly excised rat skin as a membrane. Anti-inflammatory activity of MLX gel was studied in rats and compared with the commercial formulation of piroxicam (Pirox® gel, 0.5 %, m/m). Accelerated stability studies were carried out for MLX gel for 6 months according to ICH guidelines. MLX gel was devoid of any skin irritation in rabbits. After 12 h, cumulative permeation of MLX through excised rat skin was 3.0 ± 1.2 mg cm2 with the corresponding flux value of 0.24 ± 0.09 mg cm2 h1. MLX gel exhibited significantly higher anti-inflammatory activity in rats compared to Pirox® gel. Physicochemically stable and non-irritant MLX gel was formulated which could deliver significant amounts of active substance across the skin in vitro and in vivo to elicit the anti-inflammatory activity.Primjena nesteroidnih protuupalnih lijekova na kožu ima nekoliko prednosti nad peroralnim načinom primjene uz koju se vežu određene nuspojave. U radu je opisana priprava gela meloksikama (MLX) za topičku primjenu. U pripravi gela korišten je N-metil pirolidon (NMP) kao otapalo i Carbopol ultrez 10® kao polimer za geliranje. Određivani su različiti fizikokemijski parametri kao što su pH, viskoznost i razmazljivost. Potencijalna iritacija MLX gela testirana je na kunićima, a svojstvo permeacije na svježim izrescima kože štakora. Protuupalno djelovanje praćeno je na štakorima i uspoređeno s registriranim pripravkom piroksikama (Pirox® gel, 0,5 % m/m). Testovi ubrzanog starenja MLX gela rađeni su tijekom 6 mjeseci prema ICH protokolu. Dobiveni rezultati ukazuju da MLX gel nimalo ne iritira kožu kunića. Kumulativna permeacija nakon 12 h bila je 3,0 ± 1,2 mg cm2, s odgovarajućem vrijednošću fluksa 0,24 ± 0,09 mg cm2 h1. MLX gel pokazao je značajno jače protuupalno djelovanje u odnosu na Pirox® gel. Pripravljeni gel je stabilan, ne iritira kožu, te in vitro i in vivo doprema kroz kožu ljekovitu tvar u dovoljnoj količini da ispolji protuupalno djelovanje

Predicting the solvation of organic compounds in aqueous environments: from alkanes and alcohols to pharmaceuticals

The development of accurate models to predict the solvation, solubility, and partitioning of nonpolar and amphiphilic compounds in aqueous environments remains an important challenge. We develop state-of-the-art group-interaction models that deliver an accurate description of the thermodynamic properties of alkanes and alcohols in aqueous solution. The group-contribution formulation of the statistical associating fluid theory based on potentials with a variable Mie form (SAFT-γ Mie) is shown to provide accurate predictions of the phase equilibria, including liquid–liquid equilibria, solubility, free energies of solvation, and other infinite-dilution properties. The transferability of the model is further exemplified with predictions of octanol–water partitioning and solubility for a range of organic and pharmaceutically relevant compounds. Our SAFT-γ Mie platform is reliable for the prediction of challenging properties such as mutual solubilities of water and organic compounds which can span over 10 orders of magnitude, while remaining generic in its applicability to a wide range of compounds and thermodynamic conditions. Our work sheds light on contradictory findings related to alkane–water solubility data and the suitability of models that do not account explicitly for polarity

Optimized intermolecular potential for nitriles based on Anisotropic United Atoms model

An extension of the Anisotropic United Atoms intermolecular potential model is proposed for nitriles. The electrostatic part of the intermolecular potential is calculated using atomic charges obtained by a simple Mulliken population analysis. The repulsion-dispersion interaction parameters for methyl and methylene groups are taken from transferable AUA4 literature parameters [Ungerer et al., J. Chem. Phys., 2000, 112, 5499]. Non-bonding Lennard-Jones intermolecular potential parameters are regressed for the carbon and nitrogen atoms of the nitrile group (–C≡N) from experimental vapor-liquid equilibrium data of acetonitrile. Gibbs Ensemble Monte Carlo simulations and experimental data agreement is very good for acetonitrile, and better than previous molecular potential proposed by Hloucha et al. [J. Chem. Phys., 2000, 113, 5401]. The transferability of the resulting potential is then successfully tested, without any further readjustment, to predict vapor-liquid phase equilibrium of propionitrile and n-butyronitrile

Transdermal microconduits by microscission for drug delivery and sample acquisition

BACKGROUND: Painless, rapid, controlled, minimally invasive molecular transport across human skin for drug delivery and analyte acquisition is of widespread interest. Creation of microconduits through the stratum corneum and epidermis is achieved by stochastic scissioning events localized to typically 250 μm diameter areas of human skin in vivo. METHODS: Microscissioning is achieved by a limited flux of accelerated gas: 25 μm inert particles passing through the aperture in a mask held against the stratum corneum. The particles scize (cut) tissue, which is removed by the gas flow with the sensation of a gentle stream of air against the skin. The resulting microconduit is fully open and may be between 50 and 200 μm deep. RESULTS: In vivo adult human tests show that microconduits reduce the electrical impedance between two ECG electrodes from approximately 4,000 Ω to 500 Ω. Drug delivery has been demonstrated in vivo by applying lidocaine to a microconduit from a cotton swab. Sharp point probing demonstrated full anaesthesia around the site within three minutes. Topical application without the microconduit required approximately 1.5 hours. Approximately 180 μm deep microconduits in vivo yielded blood sample volumes of several μl, with a faint pricking sensation as blood enters tissue. Blood glucose measurements were taken with two commercial monitoring systems. Microconduits are invisible to the unaided eye, developing a slight erythematous macule that disappears over days. CONCLUSION: Microscissioned microconduits may provide a minimally invasive basis for delivery of any size molecule, and for extraction of interstitial fluid and blood samples. Such microconduits reduce through-skin electrical impedance, have controllable diameter and depth, are fully open and, after healing, no foreign bodies were visible using through-skin confocal microscopy. In subjects to date, microscissioning is painless and rapid

Transdermal Drug Delivery Aided by an Ultrasound Contrast Agent: An In Vitro Experimental Study

Sonophoresis temporarily increases skin permeability such that medicine can be delivered transdermally. Cavitation is believed to be the predominant mechanism in sonophoresis. In this study, an ultrasound contrast agent (UCA) strategy was adopted instead of low frequency ultrasound to assure that cavitation occurred, and the efficacy of sonophoresis with UCA was quantitatively analyzed by optical measurements. The target drug used in this study was 0.1 % Definity® in 70% glycerol, which was delivered into porcine skin samples. Glycerol was used because it is an optical clearing agent, and the efficiency of glycerol delivery could be analyzed with optical measurements. The applied acoustic pressure was approximately 600 kPa at 1 MHz ultrasound with a 10% duty cycle for 60 minutes. Experimental results indicated that the measured relative contrast (RC) after sonophoresis with UCA was approximately 80% higher than RC after sonophoresis without UCA. In addition, the variance of RC was also reduced by more than 50% with the addition of a UCA. The use of a UCA appeared to increase cavitation, demonstrating that the use of a UCA can be effective in transdermal drug delivery (TDD)