Quasi-chemical approximation for polyatomic mixtures

The statistical thermodynamics of binary mixtures of polyatomic species was developed on a generalization in the spirit of the lattice-gas model and the quasi-chemical approximation (QCA). The new theoretical framework is obtained by combining: (i) the exact analytical expression for the partition function of non-interacting mixtures of linear $k$-mers and $l$-mers (species occupying $k$ sites and $l$ sites, respectively) adsorbed in one dimension, and its extension to higher dimensions; and (ii) a generalization of the classical QCA for multicomponent adsorbates and multisite-occupancy adsorption. The process is analyzed through the partial adsorption isotherms corresponding to both species of the mixture. Comparisons with analytical data from Bragg-Williams approximation (BWA) and Monte Carlo simulations are performed in order to test the validity of the theoretical model. Even though a good fitting is obtained from BWA, it is found that QCA provides a more accurate description of the phenomenon of adsorption of interacting polyatomic mixtures.Comment: 27 pages, 8 figure

Circular dichroism of cholesteric polymers and the orbital angular momentum of light

We explore experimentally if the light's orbital angular momentum (OAM) interacts with chiral nematic polymer films. Specifically, we measure the circular dichroism of such a material using light beams with different OAM. We investigate the case of strongly focussed, non-paraxial light beams, where the spatial and polarization degrees of freedom are coupled. Within the experimental accuracy, we cannot find any influence of the OAM on the circular dichroism of the cholesteric polymer.Comment: 3 pages, 4 figure

Evaluation of the criteria for the interpretation of the oral glucose tolerance test in the National Mother-Child Teaching Hospital ‘‘San Bartolome’’

Diabetes mellitus (DM) is a metabolic disorder that causes chronic hyperglycemia with disturbances in the metabolism of carbohydrates, fats and proteins, and alterations in microcirculation. We evaluate the criteria for the interpretation of the oral glucose tolerance test (OGTT) in the Hospital Nacional Docente Madre-Ni˜no ‘‘San Bartolomé’’ in Lima, Peru, and determine the percentages of pre-diabetic patients, diabetics that should not be included in the test, and those with alterations in their glucose curve during the biochemical determinations. To this purpose, a non-experimental, prospective cross-sectional analytic study was performed in 1271 patients, included in the study to comply with the guidelines and recommendations of the ADA and the CLSI POCT12-A3 guide, which were processed in the Biochemical Autoanalyzer Biosystems A25. Data analysis was performed using SPSS version 20.0 statistical analyzer, and respecting ethical diabetics. The main results are 1.97% diabetic and 13.85% pre-diabetic. The LJ phenomenon occurred with 6.45% (alteration in glucose curve after oral load decreases plasma glucose concentration determination after 60 min and returns at relatively higher than the basal concentration levels at 180 min) and 5.19% were poorly studied, including a >110 mg/dl baseline (p = <0.05). We determined a high rate of pre-diabetic patients and a reduced rate of diabetes coincident with Qiao et al. We highlight the usefulness of the OGTT, which must be rigorously evaluated, and reaffirm the importance of the LJ phenomenon as it may interfere with the final results of unsolved events, and evidence the importance of interindividual biological variability

Lithospheric magnetic mapping of the northern Caribbean region

A more complete crustal perspective of the northernmost part of the Venezuela Basin is provided by data from an international public database processed with new geomagnetic models (CM4) together with data from aeromagnetic surveys and from a recent marine cruise in areas offshore Puerto Rico and the Dominican Republic. The magnetic anomaly map set off three main domains: the North Atlantic plate, a narrow zone extending from the Dominican Republic to Puerto Rico-Virgin Islands, and the North Caribbean Plate. We focused mainly on the latter, applying the Euler deconvolution algorithm in the Venezuela Basin. Shallow and middle depth sources (located between 2km and 12km) are inferred to be the dominant sources (85%), while deep sources are located mostly in the Venezuela Basin, and scarcely appear in the Beata and Aves Ridges. We performed 2D+1/2 modeling on an eastwest transect, using Bouguer gravity and magnetic anomaly data to derive a more detailed crustal description of the northern part of the Venezuela Basin. The model suggests that in the Caribbean crust, long wavelengths (&gt;200km) are controlled by variations in crustal thickness, whereas the intermediate ones (50-100km) are mainly controlled by variations in their magnetic properties. It also suggests the presence of a local anomalous body located in the east-west transect, between 487km and 560km, displaying a remarkable positive magnetization contrast (0.3 SI) with regard to the rest of the basin. This body shows a slight increase in density (3010kg/m3), and extends from the bottom of the UCL (Underplate Cumulate Layer) to a depth of 7.5km. We correlate it with the volcanic wedge reported by Driscoll and Diebold (1998)

Simultaneous Irradiation of Multiple Brain Metastases with VMAT Technique: Comparison with Radiosurgery

Se estudio la aplicación de la técnica VMAT (Radioterapia de Intensidad Modulada en Arcos) con colimador ´ de 120 laminas, para la implementación de esta técnica como alternativa a la radiocirugía estereotáctica. Para ello se realizaron planes de tratamiento (simulaciones) bajo técnica VMAT, mediante planificación inversa y la posterior verificación (medición) física de los planes a 10 pacientes con múltiples metástasis cerebrales y tumor primario controlado, encontrándose un aceptable índice de conformación para esta modalidad (comparable a los de radiocirugía) en lesiones mayores a 1,5cm, así como dosis de radiación en los órganos sanos por debajo de las dosis límites de tolerancia en todos los casos.It was studied the application of VMAT technique (Volumetric Modulated Arc Therapy) with a multileaf collimator of 120 leafs, for implementation of this technique as an alternative to stereotactic radiosurgery. To achieve this goal, treatment plans (simulations) were made under VMAT technique using inverse planning and furthermore the physical verification of these plans to 10 patients with multiple brain metastases and primary tumor controlled, finding an acceptable conformation index for this modality (comparable to radiosurgery) in lesions with 1,5cm or more. The doses of radiation in the healthy organs were below the tolerance dose in all casesFil: Fajardo Freites, Jesús Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física de Líquidos y Sistemas Biológicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física de Líquidos y Sistemas Biológicos; Argentina. Universidad Central de Venezuela; VenezuelaFil: Dávila, J.. Universidad Central de Venezuela; Venezuela. Grupo de Radioterapia Oncológica; Venezuel