Determination of Thermodynamic Partial Properties in Multicomponent Systems by Titration Techniques

Thermodynamic experimental techniques using titration are usually employed to study the interaction between solutes in a diluted solution. This chapter deals with the underlying thermodynamic framework when titration technique is applied with densimetry, sound speed measurement and isothermal titration calorimetry. In the case of partial volumes and partial adiabatic compressibilities, a physical interpretation is proposed based upon atomic, free volume and hydration contributions

Design of Polymeric and Biocompatible Delivery Systems by Dissolving Mesoporous Silica Templates

There are many nanoencapsulation systems available today. Among all these, mesoporous silica particles (MSPs) have received great attention in the last few years. Their large surface-to-volume ratio, biocompatibility, and versatility allow the encapsulation of a wide variety of drugs inside their pores. However, their chemical instability in biological fluids is a handicap to program the precise release of the therapeutic compounds. Taking advantage of the dissolving capacity of silica, in this study, we generate hollow capsules using MSPs as transitory sacrificial templates. We show how, upon MSP coating with different polyelectrolytes or proteins, fully customized hollow shells can be produced. These capsules are biocompatible, flexible, and biodegradable, and can be decorated with nanoparticles or carbon nanotubes to endow the systems with supplementary intrinsic properties. We also fill the capsules with a fluorescent dye to demonstrate intracellular compound release. Finally, we document how fluorescent polymeric capsules are engulfed by cells, releasing their encapsulated agent during the first 96 h. In summary, here, we describe how to assemble a highly versatile encapsulation structure based on silica mesoporous cores that are completely removed from the final polymeric capsule system. These drug encapsulation systems are highly customizable and have great versatility as they can be made using silica cores of different sizes and multiple coatings. This provides capsules with unique programmable attributes that are fully customizable according to the specific needs of each disease or target tissue for the development of nanocarriers in personalized medicine.This research was funded by ISCIII Projects ref. PI19/00349, DTS19/00033, co-funded by ERDF/ESF, “Investing in your future”; and MICINN Projects ref. CTM2017-84050-R, Xunta de Galicia (Centro Singular de Investigación de Galicia-Accreditation 2016-2019 and EM2014/035), European Union FEDER Funds (European Regional Development Fund-ERDF), and IDIVAL for INNVAL19/18 and INNVAL20/13 and the technical support

A Source of Systematic Errors in the Determination of Critical Micelle Concentration and Micellization Enthalpy by Graphical Methods in Isothermal Titration Calorimetry

Isothermal titration calorimetry is frequently employed to determine the critical micelle concentration and the micellization enthalpy of surfactants in terms of geometrical characteristics of the titration curves. Previously we have shown theoretically that even for an infinitesimal injection, the heat per titrant mol depends on the stock solution concentration. In this work, we explore experimentally the influence of the stock solution concentration on the geometrical characteristics of the titration curve and its effect in determining the critical micelle concentration and the micellization enthalpy of surfactants. The systematic study of this phenomenology involves a great number of measurements at different temperatures with several repetitions carried out using a robotic calorimeter. As surfactant hexadecyltrimethylamonium bromide was used. The magnitude and shape of the heat titration depend on the stock solution concentration. As a consequence, the inflexion-point, break-point, and step-height decrease until a limiting value. A qualitative analysis suggests that the limiting value depends only on substance. This work shows that graphical methods could not be suitable for the calculation of the critical micelle concentration and micellization enthalpy because the magnitude and shape of the titration curve depend on the stock solution concentration. Micellar properties should be calculated by the application of theoretical models as in the ligand-binding studies

Sistema de control Country Club Chinandega : plataforma Microsoft Visual Basic.Net 2003, SQL Server 2000

Tesis (Lic. en Computación)-Universidad Nacional Autónoma de Nicaragua, León.UNAN-Leó

New Carbamates and Ureas: Comparative Ability to Gel Organic Solvents

Two series of novel amphiphilic compounds were synthesized based on carbamates and ureas structures, using a modification of the synthesis methods reported by bibliography. The compounds were tested for organic solvent removal in a model wastewater. The lipophilic group of all compounds was a hexadecyl chain, while the hydrophilic substituent was changed with the same modifications in both series. The structures were confirmed by FT-IR, NMR, molecular dynamic simulation and HR-MS and their ability to gel organic solvents were compared. The SEM images showed the ureas had a greater ability to gel organic solvents than the carbamates and formed robust supramolecular networks, with surfaces of highly interwoven fibrillar spheres. The carbamates produced corrugated and smooth surfaces. The determination of the minimum gelation concentration demonstrated that a smaller quantity of the ureas (compared to the carbamates, measured as the weight percentage) was required to gel each solvent. This advantage of the ureas was attributed to their additional N-H bond, which is the only structural difference between the two types of compounds, and their structures were corroborated by molecular dynamic simulation. The formation of weak gels was demonstrated by rheological characterization, and they demonstrated to be good candidates for the removal organic solvents

A Source of Systematic Errors in the Determination of Critical Micelle Concentration and Micellization Enthalpy by Graphical Methods in Isothermal Titration Calorimetry

Isothermal titration calorimetry is frequently employed to determine the critical micelle concentration and the micellization enthalpy of surfactants in terms of geometrical characteristics of the titration curves. Previously we have shown theoretically that even for an infinitesimal injection, the heat per titrant mol depends on the stock solution concentration. In this work, we explore experimentally the influence of the stock solution concentration on the geometrical characteristics of the titration curve and its effect in determining the critical micelle concentration and the micellization enthalpy of surfactants. The systematic study of this phenomenology involves a great number of measurements at different temperatures with several repetitions carried out using a robotic calorimeter. As surfactant hexadecyltrimethylamonium bromide was used. The magnitude and shape of the heat titration depend on the stock solution concentration. As a consequence, the inflexion-point, break-point, and step-height decrease until a limiting value. A qualitative analysis suggests that the limiting value depends only on substance. This work shows that graphical methods could not be suitable for the calculation of the critical micelle concentration and micellization enthalpy because the magnitude and shape of the titration curve depend on the stock solution concentration. Micellar properties should be calculated by the application of theoretical models as in the ligand-binding studies

Assessing the Ameliorative Effect of Selenium <i>Cinnamomum verum</i>, <i>Origanum majorana</i>, and <i>Origanum vulgare</i> Nanoparticles in Diabetic Zebrafish (<i>Danio rerio</i>)

Cinnamomum verum, Origanum majorana, and Origanum vulgare have been used in traditional medicine for a long time to treat diabetes because of their promising therapeutic effects. The combination of these plants (COO) was tested to improve their efficacy using selenium nanoparticles (Se-COO-NPs) and gum Arabic (GA) as stabilizers for sustained release. Phenolic compounds of plants were identified using liquid chromatography–mass spectrometry (LC–MS/MS). GA-Se-COO-NPs were characterized by spectroscopic and microscopic methods and evaluated in diabetic zebrafish. The ultraviolet spectrum was assessed to confirm the formation of plasmon resonance at 267 nm. The obtained particle size of selenium nanospheres was 65.76 nm. They were maintained in a stable form for 5 months at 4 °C. Transmission electron microscopy (TEM) images demonstrated the presence of individual spherical nanoparticles. Fourier transform infrared spectroscopy (FT-IR) showed the interaction between COO extract and selenium, exhibiting good entrapment efficiency (87%). The elemental analysis of COO extract and GA-COO-SeNPs confirmed that NPs were obtained. The zebrafish were exposed to a high glucose concentration for two weeks, and type 2 diabetes and oxidative stress responses were induced. In diabetic zebrafish, treatment with NPs showed antilipidemic and hypoglycemic effects, high survivability, and reduced levels of glucose, reactive oxygen species (ROS), and lipids in the blood. This group this had a higher survivorship rate than the diabetic control. The results demonstrated that GA-Se-COO-NPs have high antidiabetic potential, most likely because of the synergic effects of phenolic compounds and Se nanoparticles

Thermal Stability Evaluation of Polystyrene-Mg/Zn/Al LDH Nanocomposites

A series of samples of Mg/Zn/Al LDHs (layered double hydroxides) materials was prepared by the co-precipitation and urea hydrolysis methods. They were modified with organic surfactants (acrylate and oleate anions) and characterized by X-ray diffraction, which corroborated the intercalation of anionic species into the interlayer space. The hydrophobized materials were incorporated at low contents (10 and 15 wt.%) to polystyrene, which was synthesized by emulsion polymerization techniques. The polymeric composites were analyzed by thermogravimetry to determine the decomposition temperature. The results demonstrated that the materials with Zn presented the greatest increment in the degradation temperature (7 &deg;C &lt; T &lt; 54 &deg;C). Moreover, the Friedman, Flynn&ndash;Wall&ndash;Ozawa, and Coats&ndash;Redfern models were compared to obtain the kinetic parameters of degradation process. The obtained order of decomposition of the Coats&ndash;Redfern model showed that the decomposition process occurs in at least two stages. Finally, the addition of environmentally friendly modified Layered Double Hydroxides (LDH) nanomaterials to the polystyrene (PS) matrix allowed for obtaining polymeric composites with higher thermal stability, retarding the decomposition process of PS

Influence of Carbon Nanotubes Concentration on Mechanical and Electrical Properties of Poly(styrene-co-acrylonitrile) Composite Yarns Electrospun

In this work, the influence of carbon nanotubes (CNTs) content on the mechanical and electrical properties of four series of polymeric matrix were made and their cytotoxicity on cells was evaluated to consider their use as a possible artificial muscle. For that, polymer composite yarns were electrospun using polymeric solutions at 10 wt.%. of poly(styrene-co-acrylonitrile) P(S:AN) and P(S:AN-acrylic acid) P(S:AN-AA) at several monomeric concentrations, namely 0:100, 20:80, 40:60, 50:50 (wt.%:wt.%), and 1 wt.% of AA. Carbon nanotubes (CNTs) were added to the polymeric solutions at two concentrations, 0.5 and 1.0 wt.%. PMCs yarns were collected using a blade collector. Mechanical and electrical properties of polymeric yarns indicated a dependence of CNTs content into yarns. Three areas could be found in fibers: CNTs bundles zones, distributed and aligned CNTs zones, and polymer-only zones. PMCs yarns with 0.5 wt.% CNTs concentration were found with a homogenous nanotube dispersion and axial alignment in polymeric yarn, ensuring load transfer on the polymeric matrix to CNTs, increasing the elastic modulus up to 27 MPa, and a maximum electrical current of 1.8 mA due to a good polymer–nanotube interaction

A&P : Revista de la Facultad de Arquitectura, Planeamiento y Diseño Nº11-12

Sale este número (doble) de A&P, segunda de esta “nueva época”. No hay en este ocasión un “tema central”, sino que se tratan de distintas cuestiones con identidad y peso propio. La sección dedicada la problemática proyectual se extiende por un amplio espectro de cuestiones: la experiencia didáctica compartida por una cátedra de nuestra Facultad y una de la Facultad de Barcelona, las reflexiones de otra cátedra proyectual de la FAPyD y la exitosa participación de alumnos de dos concursos internacionales; además se suma un informe sobre el resultado del reciente concurso nacional para el Pasaje Juramento de nuestra ciudad y algunas reflexiones - no exentas de sabor a polémica - motivadas por tal concurso. Otra sección dedicada al proyecto urbano, presenta una experiencia urbanística de colegas de nuestra Casa actuando en un centro urbano del sur de la provincia de Santa Fe. Más adelante un debate no suficientemente desarrollado aún: el que tiene por objeto la conexión Rosario-Victoria. También Algunas consideraciones sobre la problemática de los monumentos, y más en general de la preservación; un estudio de la obra de un “clásico” arquitecto moderno local; un rastreo de los “constructores”de la especificidad rosarina; un informe sobre el debate urbanístico local entre el último cuarto del siglo XIX y el primer tercio del XX y por último A&P se detiene un homenaje a Jorge Borgato, profesor de tantas generaciones de arquitectos.Universidad Nacional de Rosario. Facultad de Arquitectura, Planeamiento y Diseñ