A surfactant concentration model for the systematic determination of the critical micellar concentration and the transition width

The critical micellar concentration (cmc) is a fundamental property of surfactant solutions. Many proposed methods for the definition and determination of the cmc from property-concentration plots yield values, which depend on the studied property, on the specific technique used for its analysis and in many cases on the subjective choice of the chosen type of plot and concentration interval. In this focus review, we revise the application of a surfactant concentration model we proposed earlier that defines the cmc directly based on the surfactant concentration. Known equations for the concentration-dependence of different surfactant properties can then be combined with this concentration model and fitted to experimental data. This modular concept makes it possible to determine the cmc and the transition width in a systematic and unambiguous way. We revise its use in the literature in different contexts: the determination of the cmc of surfactants and their mixtures from different properties (electrical conductivity, NMR chemical shift, self-diffusion, surface tension, UV-Vis absorption, fluorescence intensity and fluorescence correlation). We also revise the dependence of the width of the transition region on composition, detailed studies of the properties of fluorescent probes and the aggregation of non-surfactant systems, namely amyloid peptidesThis research was funded by Xunta de Galicia, grant number ED431B 2019/18S

Cinética formal

Titulación: Grao en Enxeñaría de Procesos Químicos Industriais -- Materia: Cinética QuímicaA materia Cinética Química do Grao en Enxeñaría de Procesos Químicos Industriais impártese no segundo cuadrimestre do segundo curso da titulación, polo que os alumnos xa dispón de coñecementos básicos de Química, Física e Matemáticas que son de gran utilidade para cursar esta materia. Esta materia aborda os sistemas en cambio debido a reaccións químicas, polo que é complementaria da materia Termodinámica Aplicada impartida no primeiro cuadrimestre do mesmo curso, que estuda o comportamento fisicoquímico dos sistemas en equilibrio. A materia encádrase no módulo 4 do plan de estudos da titulación, denominado Materias específicas de Enxeñaría de Procesos Químicos Industriais, e relaciónase con varias materias obrigatorias do módulo 3 (Tecnoloxía específica - Química Industrial) e en especial con Enxeñaría da Reacción Química, na que se aplican os conceptos de Cinética Química ás reaccións a nivel industrial. Esta unidade didáctica é de gran importancia na materia xa que nela sentan as bases da Cinética Química. Nesta unidade estúdanse os conceptos básicos relacionados coa velocidade das reaccións químicas, analízanse as reaccións máis sinxelas e revísanse os diferentes métodos experimentais utilizados no estudo cinético dunha reacción química. Esta unidade didáctica desenvolverase en 8 sesións presenciais de 50 minutos cada unha. Delas, 6 sesións dedicaranse a clases teóricoprácticas nas que se discuten os contidos e resólvense exercicios e problemas relacionados, e as 2 sesións restantes utilizaranse para a realización da actividade complementaria proposta. O alumno deberá dedicar unhas 18 horas adicionais de traballo persoal, fundamentalmente para a realización de exercicios e problemas e a aplicación nalgúns deles dos métodos de análise dados na actividade complementaria.Universidade de Santiago de Compostela. Servizo de Normalización Lingüístic

A base xenética da mandíbula Habsburgo

Traballo de Fin de Grao en Bioloxía. Curso 2017-2018Neste traballo abordamos a relación entre a “mandíbula Habsburgo”, un claro exemplo de prognatismo mandibular, e a alta consanguinidade nesta dinastía a través dunha análise multivariante por compoñentes principais. Os datos manexados proveñen do exame clínico de 18 trazos dismórficos indicativos de prognatismo mandibular e deficiencia maxilar en retratos pictóricos de 15 personaxes da dinastía Habsburgo. Atopamos unha asociación positiva estatísticamente significativa entre o prognatismo mandibular e o coeficiente de consanguinidade, indicando unha base xenética recesiva para este trazo. Ademais, este traballo proporciona a primeira evidencia de depresión consanguínea sobre un trazo do rostro humano

Certain aspects of maritime boundaries, with particular reference to Iraq

Abstract Not Provided

Quantitative and Qualitative Detection of Vitamin C in Some Foods by Immobilized Ascorbate Oxidase

The use of ascorbate oxidase immobilized with glass-alginate gel beads led to immobilized 93% of the enzyme original amount, the optimum pH of immobilized enzyme was 5.5, and it was stable at 5-6, but it loses 63% from its original activity at pH 7, while the optimum temperature was 4

Critical aggregation concentration for the formation of early Amyloid-β (1–42) oligomers

The oligomers formed during the early steps of amyloid aggregation are thought to be responsible for the neurotoxic damage associated with Alzheimer’s disease. It is therefore of great interest to characterize this early aggregation process and the aggregates formed, especially for the most significant peptide in amyloid fibrils, Amyloid-β(1–42) (Aβ42). For this purpose, we directly monitored the changes in size and concentration of initially monomeric Aβ42 samples, using Fluorescence Correlation Spectroscopy. We found that Aβ42 undergoes aggregation only when the amount of amyloid monomers exceeds the critical aggregation concentration (cac) of about 90 nM. This spontaneous, cooperative process resembles surfactants self-assembly and yields stable micelle-like oligomers whose size (≈50 monomers, R h ≈ 7–11 nm) and elongated shape are independent of incubation time and peptide concentration. These findings reveal essential features of in vitro amyloid aggregation, which may illuminate the complex in vivo processWe thank the Ministerio de Ciencia e Innovación, the Ministerio de Economía y Competitividad, and the Xunta de Galicia for their financial support (CTQ2010-21369, CTQ2014-59020-R, GPC2013-052, R2014/051, ED431B 2016/024, ED431D R2016/007). S.F. thanks the Xunta de Galicia for her research scholarshipS

Fluorescence Emission of Pyrene in Surfactant Solutions

This is the accepted manuscript of the following article: Piñeiro, L., Novo, M., & Al-Soufi, W. (2015). Fluorescence emission of pyrene in surfactant solutions. Advances In Colloid And Interface Science, 215, 1-12. doi: 10.1016/j.cis.2014.10.010. © 2015 Elsevier B.V. This manuscript version is made available under the CC-BY-NC-ND 4.0 license (http://creativecommons.org/licenses/by-nc-nd/4.0/)The systematic description of the complex photophysical behavior of pyrene in surfactant solutions in combination with a quantitative model for the surfactant concentrations reproduces with high accuracy the steady-state and the time resolved fluorescence intensity of pyrene in surfactant solutions near the cmc, both in the monomer and in the excimer emission bands. We present concise model equations that can be used for the analysis of the pyrene fluorescence intensity in order to estimate fundamental parameters of the pyrene-surfactant system, such as the binding equilibrium constant K of pyrene to a given surfactant micelle, the rate constant of excimer formation in micelles, and the equilibrium constant of pyrene-surfactant quenching. The values of the binding equilibrium constant KTX100 = 3300 103 M-1 and KSDS = 190 103 M-1 for Triton X-100 (TX100) and SDS micelles, respectively, show that the partition of pyrene between bulk water and micelles cannot be ignored, even at relatively high surfactant concentrations above the cmc. We apply the model to the determination of the cmc from the pyrene fluorescence intensity, especially from the intensity ratio at two vibronic bands in the monomer emission or from the ratio of excimer to monomer emission intensity. We relate the finite width of the transition region below and above the cmc with the observed changes in the pyrene fluorescence in this regionL.P. thanks the Xunta de Galicia for his research scholarships. M.N. and W.A. thank the Ministerio de Ciencia e Innovación and the Xunta de Galicia for their financial support (INCITE09262304PR, CTQ2010-21369, CN2012/314, GPC2013/052)S

Host-Guest Complexation Studied by Fluorescence Correlation Spectroscopy: Adamantane–Cyclodextrin Inclusion

The host-guest complexation between an Alexa 488 labelled adamantane derivative and β-cyclodextrin is studied by Fluorescence Correlation Spectroscopy (FCS). A 1:1 complex stoichiometry and a high association equilibrium constant of K = 5.2 × 104 M−1 are obtained in aqueous solution at 25 °C and pH = 6. The necessary experimental conditions are discussed. FCS proves to be an excellent method for the determination of stoichiometry and association equilibrium constant of this type of complexes, where both host and guest are nonfluorescent and which are therefore not easily amenable to standard fluorescence spectroscopic methods

Use of (Saccharomyces cerevisiae) Mutant in Bioremediation of Some Heavy Metals

The study aimed to use of baker’s yeast Saccharomyces cerevisiae in Bioremediation of some heavy metals and improving its capability by mutation. The dried baker's yeast from Aldnaamaya China Company used in this study. The yeast subjected to serial diagnostic tests to ensure its belongings to S. cerevisiae. To improve the ability of the yeast to remove the metals, it was mutated by Nitrosoguanidine, and among different mutants, it was found that three of them designated as Sc6-1, Sc6-2 and Sc6-3, were more resistant to the antifungal cycloheximide in a concentration of 5 and 10 µg/ ml. These mutants were selected to study their efficiency to remove metals under the specific circumstances of attachment 10 minutes, pH 6, temperature 25○C, the stirring speed 150 rpm/ min, by using an inoculums size 1×106 cells/ ml in a solution containing 1mg/L of from each metal. it was found that the mutant Sc6-2 has gain an excellent efficiency to remove of chromium, nickel, cobalt, cadmium, lead, iron and copper in combined at a rate 72.23%, while the removal efficiency of these elements by the other mutants Sc6-1 and Sc6-3 were 64.67% and 65.37% respectively

Water trees diagnostic of extruded underground cables: a case study in Saudi Arabia eastern province

In this paper, different electrical diagnostic techniques reported in the literature to predict the condition of extruded underground power cables are reviewed. Two of these techniques, namely the DC leakage current method and the DC conductivity method are applied to 14 underground cable samples rated between 15 kV and 69 kV collected from the Eastern Province of the Kingdom of Saudi Arabia. For this purpose, a setup has been constructed at the High Voltage Laboratory of King Fahd University of Petroleum & Minerals, Dhahran-Saudi Arabia. The results obtained show a correlation between the DC leakage current and the conductivity testing and the presence of water trees in the insulation material of cables. Samples suspected to have water trees are examined using the microscopic testing of the insulating material. The results obtained are in agreement with the electrical testing findings