Frequency-Dependent Dielectric Permittivity in Poisson-Nernst-Planck Model.

The approaches developed for studying the polarization of molecules and the dynamics of ions in dielectric materials are usually considered separately. The two effects are often believed to take place in different frequency ranges. The low frequency response is usually dominated by ionic migration, whereas the high frequency response is played by molecular polarization. The goal here is to clarify the interplay between free and bound charge densities and their influences on permittivity and impedance profiles by proposing a version of the Poisson-Nernst-Planck (PNP) model that allows to include the effect of a frequency-dependent (and thus not instantaneous) polarizability.

Polarization-Modulated Bent-Core Liquid Crystal Thin Films without Layer Undulation.

Spatial confinement is known to affect molecular organizations of soft matter. We present an important manifestation of this statement for thin films of bent-core smectic liquid crystals. Prior freeze-fracture transmission electron microscopy (FFTEM) studies carried out on nitro-substituted bent-core mesogens (n-OPIMB-NO_{2}) revealed an undulated smectic layer structure with an undulation periodicity of ∼8 nm. We report cryogenic TEM measurements on ∼100 nm thick 8-OPIMB-NO_{2} films. In contrast to FFTEM results, our studies show only density modulation with periodicity b=16.2 nm, and no smectic layer undulation. We show that the discrepancy between the FFTEM and cryogenic transmission electron microscopy (cryo-TEM) results can be attributed to the different sample thicknesses used in the experiments. FFTEM monitors cracked surfaces of a relatively thick (5-10 µm) frozen sample, whereas cryo-TEM visualizes the volume of a thin (0.1 µm) film that was quenched from its partially fluid phase. These results have importance in possible photovoltaics and organic electronics applications where submicron thin films are used.

Stability of anterior open bite treatment with bonded spurs associated with high-pull chincup.

OBJECTIVE: To evaluate the stability of anterior open bite (AOB) treatment with bonded spurs associated with high-pull chincup (BS/HPCC). METHODS: The experimental group consisted of 25 Class I AOB patients (15 female, 10 male) treated with BS/HPCC for 1 year. Cephalograms were analysed at pre-treatment (T1), post-treatment (T2) and at the 3-year post-treatment (T3) stage with the patients mean ages of 8.10, 9.14 and 12.18 years, respectively. The control group consisted of 23 subjects (13 female, 10 male) with normal occlusion, with comparable ages at the 3 stages (8.45, 9.45 and 12.50 years at T1, T2 and T3, respectively). T tests were used for intergroup comparisons at T1 and to compare the changes during the 3-year post-treatment period (T2-T3). Intragroup comparison in the treated group was evaluated with dependent t tests between T1 and T2. Correlations between the overbite changes in the T2-T3 period, the pre-treatment AOB severity and the amount of correction achieved during treatment were evaluated with Pearson's correlation coefficient. RESULTS: No statistically significant relapse of the AOB was found at T3. Only 1 patient had a clinically significant AOB relapse. Neither the pre-treatment AOB severity nor the amount of correction was related to overbite changes during the 3-year post-treatment period. CONCLUSIONS: There was no statistically significant relapse of the AOB, and the clinical stability of AOB correction 3-year post-treatment was of 96%.

Elastic anisotropy effects on the electrical responses of a thin sample of nematic liquid crystal.

The electrical responses of a nematic liquid crystal cell are investigated by means of the elastic continuum theory. The nematic medium is considered as a parallel circuit of a resistance and a capacitance and the electric current profile across the sample is determined as a function of the elastic constants. In the reorientation process of the nematic director, the resistance and capacitance of the sample are determined by taking into account the elastic anisotropy. A nonmonotonic profile for the current is observed in which a minimum value of the current may be used to estimate the elastic constants values. This scenario suggests a theoretical method to determine the values of the bulk elastic constants in a single planar aligned cell just by changing the direction of applied electrical field and measuring the resulting electrical current.

[Perceptions of nulliparous women about prematurity]. / Percepções de mães primigestas diante da prematuridade.

This study was made in a neonatal intensive care unit in a school hospital at Porto Alegre/RS, trying to identify the reactions of nuliparous mothers about prematurity. Ten (10) interviews with mothers of premature infants was made. The most commonly reactions were: fear, guilty, anxiety, negation, angry and depression. The mother's feeling about the team, are also observed, and classified in: positive (tranquility, safety, trust, regardless) and negative (doubt, indifference, guilty, envy and fear). A plane of nursing care was made to mothers of premature infants in neonatal intensive care unit (NICU), with the objective of humanization and improving the assistance.

[Anterior open bite. Concept, etiology, characteristics, classification and clinical cases]. / Mordida aberta anterior. Conceito, etiologia, características, classificação e casos clínicos.

The preoccupation with vertical abnormalities, and particularly anterior open bites, led the authors to establish its concept, to review the literature concerning aetiology and treatment, to propose a classification and to present three case reports of this condition.

[Thumbsucking and malocclusion--presentation of a clinical case]. / Hábito de sucção do polegar e má oclusão--apresentação de um caso clínico.

The digital sucking habit have been significantly related with the malocclusions. These problems can be observed as in the deciduous and mixed as in the permanent dentition. Frequency, length, and intensity of the habit generate as a consequence: anterior open bite, retrusion of the mandible, protrusion of the maxilla, excessive overjet, labial version of the upper incisors, uprighting of the lower incisors, posterior cross bites, sometimes associated to a ogival palate, diastema between the upper incisors, and any others facial characteristics. According to various authors, when the habit persist for an extended period after the age of four years, is considered how malocclusion cause. In this case is requered the professional interference. The presentation of this study has the objective to show the clinic conduct for preventive orthodontics in face to cases who exhib harmful habits.

[Impressions in orthodontic finishing]. / Moldagem com finalidade ortodontica.

The authors review the subject and recommend a sequence to be followed during the impression taking, starting always in the lower arch, due to its comfort and less possibility of provoking nausea, this way acquiring the patient's trust.

[Hawley appliance and its clinical use]. / A placa de Hawley e sua utilizacao clinica.

The authors presented considerations on the Hawley appliance, describing its main characteristics and modifications. It is also showed the advantages of its use, as well as its main indications: a) slight tooth inclinations and rotations; b) extrusion of posterior teeth; c) space maintener and d) as retention after orthodontic treatment.

[Importance of intermediate panoramic radiography in orthodontic treatment]. / Importância das radiografias panorâmicas intermediárias em tratamentos ortodônticos.

The authors justify the importance of the panoramic radiographs taken in the intermediary phases of the orthodontic treatment presenting a clinical case of a late developing supranumerary pre-molar.