918 resultados para Tecnopolimeri radiopachi, test di radiopacità, prove accelerate


Relevância:

30.00% 30.00%

Publicador:

Resumo:

We present a prototype that implements a set of logical rules to prove the satis ability for a class of speci cations on XML documents. Speci cations are given by means of constraints built on Boolean XPath patterns. The main goal of this tool is to test if a given speci cation is satis able or not, showing the history of the execution. It can also be used to test if a given document is a model of a given speci cation and, as a subproduct, it allows to look for all the relations (monomorphisms) between two patterns or the result of doing some operations by combining patterns in di erent ways. The results of these operations are visually shown and therefore the tool makes these operations more understandable. The implementation of the algorithm has been written in Prolog but the prototype has a Java interface for an easy and friendly use.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

I. The influence of N,N,N’,N’-tetramethylethylenediamine on the Schlenk equilibrium

The equilibrium between ethylmagnesium bromide, diethylmagnesium, and magnesium bromide has been studied by nuclear magnetic resonance spectroscopy. The interconversion of the species is very fast on the nmr time scale, and only an averaged spectrum is observed for the ethyl species. When N,N,N’,N’-tetramethylethylenediamine is added to solutions of these reagents in tetrahydrofuran, the rate of interconversion is reduced. At temperatures near -50°, two ethylmagnesium species have been observed. These are attributed to the different ethyl groups in ethylmagnesium bromide and diethylmagnesium, two of the species involved in the Schlenk equilibrium of Grignard reagents.

II. The nature of di-Grignard reagents

Di-Grignard reagents have been examined by nuclear magnetic resonance spectroscopy in an attempt to prove that dialkylmagnesium reagents are in equilibrium with alkylmagnesium halides. The di-Grignard reagents of compounds such as 1,4-dibromobutane have been investigated. The dialkylmagnesium form of this di-Grignard reagent can exist as an intramolecular cyclic species, tetramethylene-magnesium. This cyclic form would give an nmr spectrum different from that of the classical alkylmagnesium halide di-Grignard reagent. In dimethyl ether-tetrahydrofuran solutions of di-Grignard reagents containing N N,N,N’,N’-Tetramethylethylenediamine, evidence has been found for the existence of an intramolecular dialkylmagnesium species. This species is rapidly equilibrating with other forms, but at low temperatures, the rates of interconversion are reduced. Two species can be seen in the nmr spectrum at -50°. One is the cyclic species; the other is an open form.

Inversion of the carbon at the carbon-magnesium bond in di-Grignard reagents has also been studied. This process is much faster than in corresponding monofunctional Grignard reagents.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Dithiols of N-hexadecyl-3,6-di(p-mercaptophenylacetylene)carbazole (HDMC) have been synthesized and employed to form self-assembled monolayers (SAMs) on gold. One characteristic of the HDMC molecule is its peculiar molecular structure consisting of a large and rigid headgroup and a small and flexible alkyl-chain tail. HDMC adsorbates can attach to gold substrates by a strong Au-S bond with weak van der Waals interactions between the alkyl-chain tails, leading to a loosely packed hydrophobic SAM. In this way we can couple hybrid bilayer membranes (HBMs) to gold surfaces with more likeness to a cell bilayer than the conventional HBMs based on densely packed long-chain alkanethiol SAMs. The insulating properties and stability of the HDMC monolayer as well as the HDMC/lipid bilayer on gold have been investigated by electrochemical techniques including cyclic voltammetry and impedance spectroscopy. To test whether the quality of the bilayer is sufficiently high for biomimetic research, we incorporated the pore-forming protein a-hemolysin) and the horseradish peroxidase into the bilayers, respectively.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The present research examines the issue of universal interventions designed to enhance wellbeing among a community-based adolescent population. The first phase saw a cross-sectional survey conducted among Transition Year students in 13 secondary schools in Cork city and county, Republic of Ireland, with a view towards identifying dimensions linked with wellbeing (operationalised as subjective happiness, life satisfaction, and depressive symptoms) and which might prove effective in informing intervention approaches. Arising from this, mindfulness, gratitude, and cognitive-behavioural dimensions emerged as predictors of wellbeing, and short interventions (four sessions/four weeks) informed by each were conducted with participant groups in three secondary schools, one intervention in each school. Results from statistical analysis showed that the mindfulness and cognitive-behavioural interventions facilitated significant reductions in depressive symptoms among active condition participants at post-test, but that these benefits were not sustained over time, while no statistically significant changes were detected on subjective happiness and life satisfaction. The gratitude intervention was found to have had no effect on the three outcome variables. The findings are discussed in the context of theory and past research, while limitations, implications, and possible future directions are also addressed.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

We investigate the violation of Leggett's inequality for nonlocal realism using entangled coherent states and various types of local measurements. We prove mathematically the relation between the violation of the Clauser-Horne-Shimony-Holt form of Bell's inequality and Leggett's one when tested by the same resources. For Leggett inequalities, we generalize the nonlocal realistic bound to systems in Hilbert spaces larger than bidimensional ones and introduce an optimization technique that allows one to achieve larger degrees of violation by adjusting the local measurement settings. Our work describes the steps that should be performed to produce a self-consistent generalization of Leggett's original arguments to continuous-variable states.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Currently there is no reliable objective method to quantify the setting properties of acrylic bone cements within an operating theatre environment. Ultrasonic technology can be used to determine the acoustic properties of the polymerising bone cement, which are linked to material properties and provide indications of the physical and chemical changes occurring within the cement. The focus of this study was the critical evaluation of pulse-echo ultrasonic test method in determining the setting and mechanical properties of three different acrylic bone cement when prepared under atmospheric and vacuum mixing conditions. Results indicated that the ultrasonic pulse-echo technique provided a highly reproducible and accurate method of monitoring the polymerisation reaction and indicating the principal setting parameters when compared to ISO 5833 standard, irrespective of the acrylic bone cement or mixing method used. However, applying the same test method to predict the final mechanical properties of acrylic bone cement did not prove a wholly accurate approach. Inhomogeneities within the cement microstructure and specimen geometry were found to have a significant influence on mechanical property predictions. Consideration of all the results suggests that the non-invasive and non-destructive pulse-echo ultrasonic test method is an effective and reliable method for following the full polymerisation reaction of acrylic bone cement in real-time and then determining the setting properties within a surgical theatre environment. However the application of similar technology for predicting the final mechanical properties of acrylic bone cement on a consistent basis may prove difficult.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Tese de mestrado em Química Tecnológica, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2016

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Planners in public and private institutions would like coherent forecasts of the components of age-specic mortality, such as causes of death. This has been di cult to achieve because the relative values of the forecast components often fail to behave in a way that is coherent with historical experience. In addition, when the group forecasts are combined the result is often incompatible with an all-groups forecast. It has been shown that cause-specic mortality forecasts are pessimistic when compared with all-cause forecasts (Wilmoth, 1995). This paper abandons the conventional approach of using log mortality rates and forecasts the density of deaths in the life table. Since these values obey a unit sum constraint for both conventional single-decrement life tables (only one absorbing state) and multiple-decrement tables (more than one absorbing state), they are intrinsically relative rather than absolute values across decrements as well as ages. Using the methods of Compositional Data Analysis pioneered by Aitchison (1986), death densities are transformed into the real space so that the full range of multivariate statistics can be applied, then back-transformed to positive values so that the unit sum constraint is honoured. The structure of the best-known, single-decrement mortality-rate forecasting model, devised by Lee and Carter (1992), is expressed in compositional form and the results from the two models are compared. The compositional model is extended to a multiple-decrement form and used to forecast mortality by cause of death for Japan

Relevância:

30.00% 30.00%

Publicador:

Resumo:

1) Realizar un trabajo experimental con sujetos normales y deficientes de Sevilla, Córdoba y Las Palmas de Gran Canaria 2) Averiguar la correlación existente entre el test de la figura humana de F.L. Goodenough y D.B Harris y las calificaciones escolares de media general de la muestra escogida 3) Ofrecer a dichas zonas una estandarización del test de la figura humana de Goodenough y Harris, y de este modo hacer extensible a la población española un nuevo elemento más en la diagnosis de la inteligencia. 610 sujetos de escuelas normales en edades comprendidas entre los 6 y 10 años y 162 deficientes mentales de 5 a 21 años escolarizados en centros específicos, todos ellos de Sevilla y Córdoba, 500 niños de escuelas normales de Las Palmas de Gran Canaria de edades comprendidas entre 6 y 10 años y 50 sujetos de centros específicos de 9 años de edad. Analiza las bases teóricas del test de Goodenough y Harris, relaciona los estudios españoles en torno al test de Goodenough y plantea algunas hipótesis para comprobarlas con una investigación que se realiza en dos muestras con niños normales y niños deficientes mentales en las provincias españolas de Sevilla, Córdoba y Las Palmas de Gran Canaria. Test del dibujo de la figura humana de Goodenough-Harris. El test de Goodneough y Harris ha sido aplicado según las normas indicadas en el manual del Test della figura umana (ed. Organizzazioni Speciali, Firenze) en cuanto a motivar a los niños en la realización del dibujo del hombre y de la mujer y siguiendo las pautas descriptivas. Terminado el dibujo del hombre se les presentaba otra hoja para que dibujasen una mujer y concluido éste, se les presentaba un cuestionario para que lo respondiesen teniendo delante la figura del hombre y de la mujer. La aplicación del test se realizó en las primeras horas de clase, bien de la mañana o de la tarde, para evitar momentos en que los alumnos se encontrasen cansados y dicho cansancio pudiese influir en los resultados del test. Se procuró durante la aplicación del test un ambiente de relax y simpatía entre testista y alumnos y se invalidaron todos aquellos protocolos que no cumplían las normas exigidas por el test, los cuales fueron 10 en total. 1) La obtención de una correlación positiva y significativa entre el dibujo del hombre y de la mujer en ambas muestras de sujetos normales, demuestran la fidelidad del test. 2) La correlación del test tanto en el dibujo del hombre como en el de la mujer, con las notas escolares de media del curso anterior, en las áreas de ciencias naturales y dibujo, son todas ellas positivas y en su mayoría significativas, lo que significa una efectiva correlación entre el test y el rendimiento escolar. 3) el resultado de las diversas correlaciones positivas y significativas entre las notas de media del curso anterior y de estas con el test, pueden ofrecer información del tipo de inteligencia que mide el test, pudiendo predecir el éxito escolar en las áreas tratadas más que en otras materias. Sin olvidar que la predicción debe ser estudiada y profundizada. 4) No existen diferencias significativas en los resultados del test entre una edad y la inmediatamente superior, pero en general, existe diferencia significativa cuando se trata de dos años de diferencia. 5) Las diferencias entre la muestra Sevilla y Córdoba con Las Palmas de Gran Canaria son significativas, a favor de los niños andaluces. 6) En la muestra de sujetos deficientes mentales existe entre el dibujo del hombre y de la mujer una correlación positiva y significativa en todos los casos, salvo en las niñas de la muestra de Las Palmas, que aunque positiva no es significativa. Por lo cual sólo se puede hablar de una moderada correlación entre los dos dibujos. 7) Nada certero se puede afirmar respecto a las diferencias significativas de medias tanto al comparar los resultados obtenidos por los deficientes mentales niños y niñas de la muestra Sevilla y Córdoba, como al compararlos con la muestra de Las Palmas. El pequeño número de sujetos, el grado diferente de deficiencia dentro de las diversas edades no controladas harían equívocas e infundadas cualquier afirmación. 1) Entre las técnicas y los tests que se emplean con niños, el test de la figura humana es significativo, interesante y agradable, ya que a la mayoría de los sujetos les encanta dibujar y pintar. Además, tanto los sujetos normales como los deficientes dibujan, en numerosas ocasiones, figuras humanas. La representación del dibujo de la persona humana en sus diversas etapas es un reflejo del desarrollo intelectual del niño, puesto que el niño no pinta lo que ve sino lo que sabe. Por consiguiente, los resultado con el uso del test utilizado han sido satisfactorios tanto en normales como en deficientes.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Trabajo que recoge los resultados tras la aplicación del test de Raven en diferentes grupos de EGB para conocer de manera objetiva la realidad de los alumnos españoles de este nivel educativo. Todo ello va precedido por unas normas simplificadas de aplicación, acompañadas de las que dió el autor del test, y un estudio sintético y práctico de las variadas y diversas potencialidades del mismo encaminadas al conocimiento exhaustivo del examinando, así como diversas observaciones prácticas del autor..

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The no response test is a new scheme in inverse problems for partial differential equations which was recently proposed in [D. R. Luke and R. Potthast, SIAM J. Appl. Math., 63 (2003), pp. 1292–1312] in the framework of inverse acoustic scattering problems. The main idea of the scheme is to construct special probing waves which are small on some test domain. Then the response for these waves is constructed. If the response is small, the unknown object is assumed to be a subset of the test domain. The response is constructed from one, several, or many particular solutions of the problem under consideration. In this paper, we investigate the convergence of the no response test for the reconstruction information about inclusions D from the Cauchy values of solutions to the Helmholtz equation on an outer surface $\partial\Omega$ with $\overline{D} \subset \Omega$. We show that the one‐wave no response test provides a criterion to test the analytic extensibility of a field. In particular, we investigate the construction of approximations for the set of singular points $N(u)$ of the total fields u from one given pair of Cauchy data. Thus, the no response test solves a particular version of the classical Cauchy problem. Also, if an infinite number of fields is given, we prove that a multifield version of the no response test reconstructs the unknown inclusion D. This is the first convergence analysis which could be achieved for the no response test.