536 research outputs found
Pulsed laser deposition of KNbO<sub>3</sub> thin films
The laser ablation of stationary KNbO3 single crystal targets induces a Nb enrichment of the target surface. In rotated targets this effect is observed only in those areas irradiated with low laser fluence. The composition of the plasma formed close to the target surface is congruent with the target composition; however, at further distances K-deficient films are formed due to the preferential backscattering of K in the plasma. This loss may be compensated for by using K-rich ceramic targets. Best results so far have been obtained with [K]/[Nb] = 2.85 target composition, and crystalline KNbO3 films are formed when heating the substrates to 650 °C. Films formed on (100)MgO single crystals are usually single phase and oriented with the (110) film plane parallel to the (100) substrate surface. (100)NbO may coexist with KNbO3 on (100)MgO. At substrate temperatures higher than 650 °C, niobium diffuses into MgO forming Mg4Nb2O9 and NbO, leading to K evaporation from the film. Films formed on (001) alpha-Al2O3 (sapphire) show the coexistence of (111), (110), and (001) orientations of KNbO3, and the presence of NbO2 is also observed. KNbO3 films deposited on (001)LiNbO3 crystallize with the (111) plane of the film parallel to the substrate surface. For the latter two substrates the Nb diffusion into the substrate is lower than in MgO and consequently the K concentration retained in the film is comparatively larger
Substrate influence on the ferroelectric properties of PTCa thin films
[ES] Se han estudiado las propiedades ferroeléctricas de láminas delgadas de titanato de plomo modificado con calcio
(Pb0.76Ca0.24)TiO3 (PTCa) preparadas vĂa sol gel mediante cristalizaciones sucesivas sobre tres tipos de substratos: (A) Pt / Ti /
SiO2 / Si (100), (B) Ti / Pt / Ti / SiO2 / Si(100) y (C) Pt / TiO2 / SiO2 /Si (100). Los resultados de la caracterización ferroeléctrica
muestran valores del coeficiente piroeléctrico espontáneo entorno a » 5 .10-9 C cm-2 K-1. La baja conmutabilidad de las
laminas facilita la estabilización del valor del coeficiente piroeléctrico en el tiempo. Un tratamiento térmico posterior de recocido
a 650ºC 1 hora produce cambios en las propiedades ferro-piezoeléctricas que se pueden asociar con modificaciones de la
textura en las láminas.[EN] The ferroelectric properties of calcium modified lead titanate (Pb0.76Ca0.24)TiO3 (PTCa) thin films prepared by a sol - gel method
with successive crystallisations on three different substrates (A) Pt / Ti / SiO2 / Si (100), (B) Ti / Pt / Ti / SiO2 / Si(100)
y (C) Pt / TiO2 / SiO2 /Si (100), have been studied. The results of the ferroelectric characterisation show values of the spontaneous
pyroelectric coefficient close to » 5 .10-9 C cm-2 K-1. The low switching properties favour the stabilisation in time of the
pyroelectric coefficient value. Alatter annealing thermal treatment (650ÂşC 1h) produces changes in the ferro - piezoelectric properties
that can be related with changes in the texture of the films.Este trabajo ha sido realizado mediante la financiaciĂłn recibida
de los proyectos MAT98 - 1068 (CICYT) y BRPR - CT98 -
0777 (BRITE EURAM de la U.E.).Peer reviewe
Non-volatility of ferroelectric SBT thin fims, at 75ÂşC
[ES] El estudio de la no volatilidad de una memoria FeRAM de tantalato de bismuto y estroncio, SrBi2Ta2O9 (SBT) en condiciones
reales de uso, requiere la caracterización ferroeléctrica del material en forma de lámina delgada a temperaturas por encima
del ambiente. Para ello se han depositado láminas de SBT mediante un método sol-gel, sobre substratos de
Pt/TiO2/SiO2/Si(100), seleccionándose condensadores de área 5.10-4 cm-2. Basándonos en las medidas de la variación de la
polarizaciĂłn con el tiempo (retenciĂłn) realizadas a temperatura ambiente y a 75ÂşC, analizamos la viabilidad del material
como una FeRAM en condiciones reales de uso.[EN] The study of the non-volatility of Strontium bismuth tantalate SrBi2Ta2O9 (SBT) FeRAM memory, at real operating conditions,
requires the ferroelectric characterisation of the material, as a thin film, above the room temperature.As a result, it has been
deposited SBT films by the sol-gel method, onto Pt/TiO2/SiO2/Si (100) substrates, using capacitors of 5 x 10–4 cm-2 .In this
work, we analysed the viability of this material as a FeRAM memory in real operating conditions, as a result of the variation
of the polarisation measurements with time (retention), performed at room temperature and 75ÂşC.Este trabajo ha sido realizado con el apoyo del proyecto de
la CICYT MAT98-1068.Peer reviewe
Feasibility of (Pb, Ca)TiO3 thin films deposited on Pt/TiO2/SiO2/Si(100) for switching applications
[ES] Se han depositado láminas delgadas de (Pb,Ca)TiO3 sobre substratos de Pt/TiO2/SiO2/Si(100) por centrifugación, partiendo
de soluciones sintetizadas por sol -gel. La concentraciĂłn de las soluciones y el contenido de PbO se seleccionaron para minimizar
las tensiones de las láminas cristalizadas y obtener la adecuada estequiometria. La cristalización mediante un calentamiento
rápido (RTP), conduce a láminas con orientaciones preferentes [001]/[001], reducida capa interfacial ferroeléctrico-Pt
y composición deseada. Los parámetros ferroeléctricos obtenidos muestran una mejora de las propiedades. Estas láminas presentan
una fatiga y envejecimiento mucho más moderados que otros materiales alternativos depositados sobre substratos
iguales, lo que permite considerar al método descrito como muy valioso para conseguir materiales susceptibles de emplear en
aplicaciones de conmutaciĂłn.[EN] (Pb,Ca)TiO3 ferroelectric thin films have been spin-coated on Pt/TiO2/SiO2/Si(100) substrates from sol-gel synthesized solutions.
Selecting the solution concentrations and the excess of PbO content, stoichiometric composicion with reduced strains are
obtained. Crystallization process by rapid thermal treatment (RTP) promote preferred orientations [001]/[100] resulting a thiner
ferroelectric-platinum interface layer, which causes the improvement of fatigue and retain behaviour, despite the use of
platinum electrodes. These experimental finds let to cosider the described methode of processing very convenient to prepare
thin films of this composition to use on switching applications such as non volatil RAM memories.Peer reviewe
Antecedents and Outcome of Union Commitment
There is an apparent decline in union membership across industries in the Philippines. The study tried to understand this phenomenon by determining factors that lead to union commitment using a framework derived from existing models of union commitment and participation. Survey data were gathered from 194 union members belonging to academic and financial institutions, and pharmaceutical industries. Path analysis was used to analyze the data. The resulting model verified that organization commitment, perceived union instrumentality, pro-union attitude, and union socialization are predictors of union commitment. Furthermore, union commitment leads to union participation. Findings suggest that unions may enhance member commitment and participation in union activities by utilizing informal socialization practices
Developing Culturally Responsive Psychological Services for Micronesian International Students in Guam
The resident-as-teacher educational challenge: a needs assessment survey at the National Autonomous University of Mexico Faculty of Medicine
<p>Abstract</p> <p>Background</p> <p>The role of residents as educators is increasingly recognized, since it impacts residents, interns, medical students and other healthcare professionals. A widespread implementation of resident-as-teacher courses in developed countries' medical schools has occurred, with variable results. There is a dearth of information about this theme in developing countries. The National Autonomous University of Mexico (UNAM) Faculty of Medicine has more than 50% of the residency programs' physician population in Mexico. This report describes a needs assessment survey for a resident as teacher program at our institution.</p> <p>Methods</p> <p>A cross-sectional descriptive survey was developed based on a review of the available literature and discussion by an expert multidisciplinary committee. The goal was to identify the residents' attitudes, academic needs and preferred educational strategies regarding resident-as-teacher activities throughout the residency. The survey was piloted and modified accordingly. The paper anonymous survey was sent to 7,685 residents, the total population of medical residents in UNAM programs in the country.</p> <p>Results</p> <p>There was a 65.7% return rate (5,186 questionnaires), a broad and representative sample of the student population. The residents felt they had knowledge and were competent in medical education, but the majority felt a need to improve their knowledge and skills in this discipline. Most residents (92.5%) felt that their role as educators of medical students, interns and other residents was important/very important. They estimated that 45.5% of their learning came from other residents. Ninety percent stated that it was necessary to be trained in teaching skills. The themes identified to include in the educational intervention were mostly clinically oriented. The educational strategies in order of preference were interactive lectures with a professor, small groups with a moderator, material available in a website for self-learning, printed material for self-study and homework, and small group web-based learning.</p> <p>Conclusions</p> <p>There is a large unmet need to implement educational interventions to improve residents' educational skills in postgraduate educational programs in developing countries. Most perceived needs of residents are practical and clinically oriented, and they prefer traditional educational strategies. Resident as teachers educational interventions need to be designed taking into account local needs and resources.</p
Structured Resistance Training Improves Self-Esteem and Strength in Previously Untrained College Females
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