Comparison between one-dimensional uncoupled and convection-conduction conjugated approaches in finned surface heat transfer

This work studies the forced convection problem in internal flow between concentric annular ducts, with radial fins at the internal tube surface. The finned surface heat transfer is analyzed by two different approaches. In the first one, it is assumed one-dimensional heat conduction along the internal tube wall and fins, with the convection heat transfer coefficient being a known parameter, determined by an uncoupled solution. In the other way, named conjugated approach, the mathematical model (continuity, momentum, energy and K-epsilon equations) applied to tube annuli problem was numerically solved using finite element technique in a coupled formulation. At first time, a comparison was made between results obtained for the conjugated problem and experimental data, showing good agreement. Then, the temperature profiles under these two approaches were compared to each other to analyze the validity of the one-dimensional classical formulation that has been utilized in the heat exchanger design.

Sera from chronic chagasic patients depress cardiac electrogenesis and conduction

We report results obtained with sera from 58 chronic chagasic patients that were evaluated for effects on heart rate and atrioventricular (AV) conduction in isolated rabbit hearts and screened for the presence of muscarinic and beta-adrenergic activity. We show that sera from 26 patients decreased heart rate, while 10 increased it and 22 had no effect. Additionally, sera from 20 of the 58 patients blocked AV conduction. Muscarinic activation seems to be involved in both effects, but is not the only mechanism, since atropine did not antagonize the decrease in heart rate in 23% of sera or AV block in 40%. Sera from patients with complex arrhythmias were significantly more effective in depressing both heart rate and AV conduction. Sera that induce increases in heart rate seem to operate exclusively through beta-adrenergic activation. Two of these sera, evaluated with respect to intercellular communication in primary cultures of embryonic cardiomyocytes were able to block gap junction conductance evaluated by a dye injection technique after 24-h exposure. The mechanisms underlying this uncoupling effect are currently being investigated.

Performance of a Brazilian population sample in the Boston Diagnostic Aphasia Examination: A pilot study

Brazilian researchers and health professionals often face the challenge of having to use tests developed in foreign languages and standardized for populations of other countries, especially in the fields of Neuropsychology and Neurolinguistics. This fact promotes a feeling that some scoring systems may be inadequate for our sociocultural reality. In the present study, we describe the performance of a Brazilian population sample submitted to a translated and adapted version of the Boston Diagnostic Aphasia Examination (BDAE). Sixty normal volunteers (21 men and 39 women), all Portuguese native speakers, ranging in age from 15 to 78 years (average 43.7) and with an educational level of 2 to 16 years (average 9.9), were tested using a translated and adapted Portuguese version of the BDAE. Cut-off scores are suggested for our population and the performance of the Brazilian sample is compared to that of American and Colombian samples, with the results being closely similar in all tasks. We also performed a correlation analysis between age, gender and educational level and the influence of these variables on the performance of the subjects. We found no statistically significant differences between genders. Educational level correlated positively with performance, especially in the subtests involving reading and writing. There was a negative correlation between age and performance in two subtests (Visual Confrontation Naming and Sentences to Dictation), but a coexisting effect of educational level could not be ruled out.

Normative data for the Brazilian population in the Boston Diagnostic Aphasia Examination: influence of schooling

In Neurolinguistics, the use of diagnostic tests developed in other countries can create difficulties in the interpretation of results due to cultural, demographic and linguistic differences. In a country such as Brazil, with great social contrasts, schooling exerts a powerful influence on the abilities of normal individuals. The objective of the present study was to identify the influence of schooling on the performance of normal Brazilian individuals in the Boston Diagnostic Aphasia Examination (BDAE), in order to obtain reference values for the Brazilian population. We studied 107 normal subjects ranging in age from 15 to 84 years (mean ± SD = 47.2 ± 17.6 years), with educational level ranging from 1 to 24 years (9.9 ± 4.8 years). Subjects were compared for scores obtained in the 28 subtests of the BDAE after being divided into groups according to age (15 to 30, N = 24, 31 to 50, N = 33 and 51 years or more, N = 50) and education (1 to 4, N = 26, 5 to 8, N = 17 and 9 years or more, N = 61). Subjects with 4 years or less of education performed poorer in Word Discrimination, Visual Confrontation Naming, Reading of Sentences and Paragraphs, and Primer-Level Dictation (P < 0.05). When breakdown by schooling was 8 years or less, subjects performed poorer in all subtests (P < 0.05), except Responsive Naming, Word Recognition and Word-Picture Matching. The elderly performed poorer (P < 0.05) in Complex Ideational Material, Visual Confrontation Naming, Comprehension of Oral Spelling, Written Confrontation Naming, and Sentences to Dictation. We present the reference values for the cut-off scores according to educational level.

A study of the abilities in oral language comprehension of the Boston Diagnostic Aphasia Examination - Portuguese version: a reference guide for the Brazilian population

We analyzed the performance of 162 normal subjects, subdivided into groups according to age and schooling, in the oral comprehension tasks of the Boston Diagnostic Aphasia Examination translated and adapted to Brazilian Portuguese to obtain a profile of performance for the Brazilian population, as well as cut-off scores for each task, and to determine the best combination of tasks that distinguish normal from aphasic subjects, as a guide for clinicians. The normal subjects were compared to 69 aphasics. Age alone influenced the performance in the designation of actions (subjects above 70 years showing the worst performance); schooling alone influenced the comprehension of forms, colors and numbers (subjects with less than four years of education showing a poorer performance). Both age and schooling influenced the performance in Body Part Identification (BPI) and Complex Ideational Material (CIM) with mean values of 70.5 ± 3.3 (Word Discrimination, WD), 18.9 ± 1.4 (BPI), 14.7 ± 0.9 (Commands), and 10.3 ± 1.7 (CIM) for the whole sample; the cut-off scores obtained were 65 (WD), 17.5 (BPI), 14 (Commands), and 9.5 (CIM) for the whole sample. Logistic regression showed that the combination of BPI + Commands + CIM was the most efficient in differentiating normal subjects from aphasics, with 72.5% sensitivity and 97.6% specificity. However, for low-education subjects, BPI and Commands were sufficient for this differentiation (75.7% sensitivity and 84.7% specificity). The main contribution of this study was to provide reference values that are far more representative of our population to be used by health professionals in Brazil, taking into account cultural differences.

Novel word learning ability in chronic post-stroke aphasia : variability and modality effects

Novel word learning has been rarely studied in people with aphasia (PWA), although it can provide a relatively pure measure of their learning potential, and thereby contribute to the development of effective aphasia treatment methods. The main aim of the present thesis was to explore the capacity of PWA for associative learning of word–referent pairings and cognitive-linguistic factors related to it. More specifically, the thesis examined learning and long-term maintenance of the learned pairings, the role of lexical-semantic abilities in learning as well as acquisition of phonological versus semantic information in associative novel word learning. Furthermore, the effect of modality on associative novel word learning and the neural underpinnings of successful learning were explored. The learning experiments utilized the Ancient Farming Equipment (AFE) paradigm that employs drawings of unfamiliar referents and their unfamiliar names. Case studies of Finnishand English-speaking people with chronic aphasia (n = 6) were conducted in the investigation. The learning results of PWA were compared to those of healthy control participants, and active production of the novel words and their semantic definitions was used as learning outcome measures. PWA learned novel word–novel referent pairings, but the variation between individuals was very wide, from more modest outcomes (Studies I–II) up to levels on a par with healthy individuals (Studies III–IV). In incidental learning of semantic definitions, none of the PWA reached the performance level of the healthy control participants. Some PWA maintained part of the learning outcomes up to months post-training, and one individual showed full maintenance of the novel words at six months post-training (Study IV). Intact lexical-semantic processing skills promoted learning in PWA (Studies I–II) but poor phonological short-term memory capacities did not rule out novel word learning. In two PWA with successful learning and long-term maintenance of novel word–novel referent pairings, learning relied on orthographic input while auditory input led to significantly inferior learning outcomes (Studies III–IV). In one of these individuals, this previously undetected modalityspecific learning ability was successfully translated into training with familiar but inaccessible everyday words (Study IV). Functional magnetic resonance imaging revealed that this individual had a disconnected dorsal speech processing pathway in the left hemisphere, but a right-hemispheric neural network mediated successful novel word learning via reading. Finally, the results of Study III suggested that the cognitive-linguistic profile may not always predict the optimal learning channel for an individual with aphasia. Small-scale learning probes seem therefore useful in revealing functional learning channels in post-stroke aphasia.

Reliability of muscle fiber conduction velocity in the tibialis anterior

This document could not have been completed without the hard work of a number of individuals. First and foremost, my supervisor, Dr. David Gabriel deserves the utmost recognition for the immense effort and time spent guiding the production of this document through the various stages of completion. Also, aiding in the data collection, technical support, and general thought processing were Lab Technician Greig Inglis and fellow members of the Electromyographic Kinesiology Laboratory Jon Howard, Sean Lenhardt, Lara Robbins, and Corrine Davies-Schinkel. The input of Drs. Ted Clancy, Phil Sullivan and external examiner Dr. Anita Christie, all members ofthe assessment committee, was incredibly important and vital to the completion of this work. Their expertise provided a strong source of knowledge and went to ensure that this project was completed at exemplary level. There were a number of other individuals who were an immense help in getting this project off the ground and completed. The donation of their time and efforts was very generous and much needed in order to fulfill the requirements needed for completion of this study. Finally, I cannot exclude the contributions of my family throughout this project especially that of my parents whose support never wavers.

Rôle de la voie rapide dans les propriétés de conduction cachée du noeud AV de lapin

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Mechanism of electrical conduction in plasma polymerized furfural thin films

Polyfurfural thin films lying in the thickness range of 1300–2000 A˚ were prepared by ac plasma polymerization technique. The current–voltage characteristics in symmetric and asymmetric electrode configuration were studied with a view to determining the dominant conduction mechanism.It was found that the Schottky conduction mechanism is dominant in plasma polymerized furfural thin films.The predominance of Schottky mechanism was further confirmed based on the thermally stimulated current measurements.

Thermal Conduction in Polymeric Nanofluids and Nanosolids Controlled by Interfacial Scattering:Solutions to Some Selected Problems

Dept.of Instrumentation,Cochin University of Science and Technology

Elecrical conduction and dielectric behaviour of thin films of vacuum evaporated amorphous silicon, hydrogenated amorphous silicon and chemically deposited cadmium sulphide

A brief account of the several methods used for the production of thin films is presented in this Chapter. The discussions stress on the important methods used for the fabrication of a-si:H thin films. This review' also reveals ‘that almost all the general methods, like vacuum evaporation, sputtering, glow discharge and even chemical methods are currently employed for the production of a-Si:H thin films. Each method has its own advantages and disadvantages. However, certain methods are generally preferred. Subsequently a detailed account of the method used here for the preparation of amorphous silicon thin films and their hydrogenation is presented. The metal chamber used for the electrical and dielectric measurements is also described. A brief mention is made-on the electrode structure, film area and film geometry.

Evidence for polaron conduction in nanostructured manganese ferrite

Nanoparticles of manganese ferrite were prepared by the chemical co-precipitation technique. The dielectric parameters, namely, real and imaginary dielectric permittivity (ε and ε ), ac conductivity (σac) and dielectric loss tangent (tan δ), were measured in the frequency range of 100 kHz–8MHz at different temperatures. The variations of dielectric dispersion (ε ) and dielectric absorption (ε ) with frequency and temperature were also investigated. The variation of dielectric permittivity with frequency and temperature followed the Maxwell–Wagner model based on interfacial polarization in consonance with Koops phenomenological theory. The dielectric loss tangent and hence ε exhibited a relaxation at certain frequencies and at relatively higher temperatures. The dispersion of dielectric permittivity and broadening of the dielectric absorption suggest the possibility of a distribution of relaxation time and the existence of multiple equilibrium states in manganese ferrite. The activation energy estimated from the dielectric relaxation is found to be high and is characteristic of polaron conduction in the nanosized manganese ferrite. The ac conductivity followed a power law dependence σac = Bωn typical of charge transport assisted by a hopping or tunnelling process. The observed minimum in the temperature dependence of the frequency exponent n strongly suggests that tunnelling of the large polarons is the dominant transport process