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.

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 °C < T < 54 °C). Moreover, the Friedman, Flynn-Wall-Ozawa, and Coats-Redfern models were compared to obtain the kinetic parameters of degradation process. The obtained order of decomposition of the Coats-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.

Fluorinated hydrotalcites: the addition of highly electronegative species in layered double hydroxides to tune basicity.

Hydrotalcite-like compounds were synthesized by coprecipitation using a constant-pH method. Aluminum was introduced in the form of an octahedral aluminum fluorine complex during the synthesis. Controlling the pH during the synthesis ensured that aluminum fluorine did not decompose to tetrahedral species but remained in the octahedral (AlF(6))(3-) form to be incorporated into brucite-like sheets. The physicochemical, thermal, and spectroscopic characterizations showed significant modifications by fluorine introduction regarding structural, textural, and adsorption properties. The memory effect of fluorinated hydrotalcites differed from the memory effect commonly observed in fluorine-free hydrotalcites. Nitromethane adsorption showed that the basicity of hydrotalcite was greatly modified by the fluorine loading.

Descompresión quirúrgica de grandes lesiones maxilares: reporte de casos clínicos / Surgical decompression of large jaw injury: clinical case report

Existen lesiones de considerable tamaño ubicadas tanto en el maxilar como en la mandíbula que constituyen una entidad propia con típicos hallazgos histopatológicos. Este tipo de lesiones son localmente agresivas y presentan una frecuente tendencia recidivante como lo son por ejemplo los tumores odontogénicos quísticos queratinizantes El tratamiento de los mismos sigue siendo controversial. Como conceptos terapéuticos están la marsupialización, la resección de las lesiones de gran tamaño y la descompresión quirúrgica de las mismas, siendo este último en particular el objeto de estudio del presente trabajo. Se presentan dos casos de pacientes con Síndrome de Nevus de Células Basales (también conocido como Síndrome de Gorlin - Goltz) el cual es un desorden autosómico dominante en el que aparecen múltiples alteraciones, las más frecuentes son la presencia de carcinomas de células basales en piel, los Tumores Odontogénicos Quísticos Queratinizantes en los huesos maxilares y otras alteraciones óseas, en dichos casos se valora la importancia de la historia clínica, el examen radiológico y tomográfico, el estudio histopatológico y el papel del odontólogo, ya que su diagnóstico se puede establecer en base a los tumores odontogénicos quísticos queratinizantes que se encuentren y a la interconsulta con médicos especialistas y a estudios complementarios como la radiografía de tórax. El tratamiento que se utilizó en ambos casos fue realizado en dos fases, en una primera etapa se realizó la descompresión quirúrgica de la lesión con el fin de evitar complicaciones tales como fracturas mandibulares, lesiones a dientes y estructuras vecinas; posteriormente se llevó a cabo la enucleación total en conjunto con la osteotomía periférica.

There are considerably big lesions, located in the maxilla and jaw that constitutes an entity with typical histological characteristics. These lesions are locally aggressive and have an important tendency to recidivate, for example, keratinizing odontogenic cystic tumors. The treatment of this entity continues being controversial. As therapeutic options marsupialization, resection of big lesions and surgical decompression has been used, being the last one particularly the subject of study in this work. Two cases of patients with basal cell nevus syndrome are presented, known as Gorlin Goltz syndrome too, which is an autosomal disorder characterized by multiple alterations, the more common are the presence of nevoid basal cell carcinoma in skin, keratinizing odontogenic cystic tumors in the maxilla and jaw, and other bone alterations. In this cases the clinic history or anamnesis, radiologic and tomographic studies, histopathological study and the dentist role are highly valued because diagnostic can be established studying the keratinizing odontogenic cystic tumors, consultation with other specialists and studying complementary studies like thoracic radiography. The treatment performed in both cases was biphasic; first phase consisted in surgical decompression of lesion to avoid complications like mandibular fracture, tooth lesions and neighbor structures damage, after that in the second phase enucleation of the lesion was made with peripheral osteotomy.

Lesiones más frecuentes en glándulas salivales menores presentes en lengua: reivisión bibliográfica / Injuries more common in minor salivary glands present in language: a literature review

La producción de saliva es una de las principales funciones que cumplen los órganos presentes en la cavidad bucal, esta labor la desarrollan las glándulas salivales, tanto mayores como menores. Estas últimas se encuentran distribuidas en diversas zonas de la cavidad bucal, como lengua, labios, paladar y carrillos. En la lengua pueden encontrase las glándulas de Blandin y Nuhn, Weber y Von Ebner. Dichas glándulas pueden ser asiento de diversas patologías tanto benignas como malignas, el objetivo de esta revisión bibliográfica es dar a conocer las distintas alteraciones que se pueden presentar, sus características y tratamiento

The production of saliva is the principal functions that fulfill the present organs in the oral cavity, the salivary glands develop this labor, as major as minors. The above mentioned are distributed in diverse zones of the oral cavity, like tongue, lips, palate and jowl. In the tongue they can be finding the glands of Blandin and Nuhn, Weber and Von Ebner. The above mentioned glands can be a seat of diverse both benign and malignant pathologies, the aim of this bibliographic revision is to announce the different alterations that they can present, her characteristics and treatment

Structural and textural evolution during folding of layers of layered double hydroxides.

Layers of a layered double hydroxide, containing aluminum 4-fold coordinated, were partially folded in order to obtain a fibrous hydrotalcite-like compound. The hydrotalcite layers, in the presence of an anionic surfactant (sodium dodecyl sulfate) after hydrothermal treatment for 2 weeks, acquire a mesoporous-like arrangement. The transformation was monitored by techniques sensitive to structural and textural properties. Results suggest that brucite-like layers can be joined throughout unsaturated coordinated aluminum, that is, tetrahedral aluminum which links through hydrogen bonds to form aluminum octahedrally coordinated. The fractal dimension parameter was very sensitive to evolution from layered to fibrous hydrotalcites.

Ubicación anatómica de las glándulas salivales linguales ó glandulas salivales menores presentes en la lengua / Anatomical location of lingual salivary glands or minor salivary glands present in the language

La cavidad bucal está conformada por diversas estructuras anatómicas, donde las glándulas salivales desempeñan funciones de vital importancia como son la producción y excreción de saliva. Las mismas se dividen en glándulas salivales mayores y menores. Las glándulas salivales mayores son las glándulas parótidas, las submaxilares y las sublinguales. Las glándulas salivales menores están distribuidas en diferentes localizaciones anatómicas de la mucosa bucal. Ellas son: las glándulas labiales, palatinas, genianas y linguales. Éstas últimas a su vez están conformadas por las glándulas de Blandin y Nühn, Weber y Von Ebner. El objetivo de este trabajo es destacar la importancia de estas glándulas en cuanto a su ubicación anatómica, inervación é irrigación

The oral cavity is formed by different anatomic structures; in wich the salivary glands have important vital functions such as production and excretion of saliva. These glands are divided in two groups: mayor salivary glands and minor salivary glands. The mayor salivary glands are the parotid, submaxilar and sublingual glands. The minor salivary glands are distributed in different anatomic locations in the oral cavity. These glands are: the labial glands, the palatine glands, the genians glands and the lingual glands. These lingual glands are also formed by the Blandin and Nuhn glands, the Weber glands and the Von Ebner glands. The objective of this work is to determine the importance of these glands in matter of their anatomic location, inervation and irrigation

Hipertensión arterial, obesidad y herencia en la ocurrencia de la diabetes mellitus no dependiente de insulina / Arterial hypertension, obesity and family history in non-insuline dependent diabetes mellitus

Recientemente se ha postulado la existencia de un síndrome de resistencia a la insulina caracterizado, entre otros eventos, por diabetes mellitus no dependiente de insulina (DMNDI), obesidad, hipertensión arterial, cardiopatía isquémica y dislipidemia. Para estudiar la asociación existente entre DMNDI, cardiopatía isquémica y dislipidemia, obesidad, hipertensión arterial entre éstos y los antecedentes familiares de diabetes se realizó un estudio transversal con los registros del programa de detección oportuna de diabetes de la Unidad de Medicina Familiar No. 21 del Instituto Mexicano del Seguro Social. Se estudiaron 26,069 pacientes. Los hipertensos tuvieron dos veces mayor riesgo de padecer DMNDI (Razón de momio (RM) 2.1; IC 95 por ciento 1.4-3.3) similar a lo observado en los obesos (RM 1.6;IC 95 por ciento 1.0-2.8), y en aquéllos con historia familiar de diabetes (RM 1.8;IC 95 por ciento 1.2-2.7). La DMNDI es muy frecuente en la población mexicana, probablemente por una mayor predisposición genética al síndrome de resistencia a la insulina