Trilled sounds in Brazilian Portuguese: Phonetic and phonological characterization

This paper deals with the phonological definition of trills in Brazilian Portuguese. The phonemic existence of two distinctive R's, one soft the other strong, is taken for granted. After reviewing the ideas of some Portuguese-speaking phoneticians on this matter, 146 occurrences of R's - recorded by two informants - were acoustically analyzed, the formants' general aspect and the length of the R segments were studied in the resulting spectrograms. The phonological table displayed in the conclusion does not include any trill. The soft phoneme /r/, instead, is classified as an interrupted apico-alveolar tap with a retroflex allophone. Naturalization between these two units is discarded.t

Prevention of experimental venous thrombosis induced by contrast medium in the rat

In order to assess experimentally the usefulness of some procedures employed in man to prevent venous thrombosis following phlebography, thrombosis was induced in rats using sodium diatrizoate in a temporarily isolated segment of a jugular vein. The prevention of thrombosis was attempted by washing out the vein with physiologic saline or saline plus heparin or by injecting saline plus heparin in the opposite jugular vein. Thrombosis occurred in all animals in the control group and in the group treated with saline alone. Both treatment schemes with heparin significantly reduced the incidence of thrombosis, the wash out with heparin being more effective than systemic heparin.

Niobium filtration of conventional and high-frequency x-ray generator beams for intraoral radiography. Effects on absorbed doses, image density and contrast, and photon spectra

We have studied the effects of niobium beam filtration on absorbed doses, on image density and contrast, and on photon spectra with conventional and high-frequency dental x-ray generators. Added niobium reduced entry and superficial absorbed doses in periapical radiography by 9% to 40% with film and digital image receptors, decreased the radiation necessary to produce a given image density on E-speed film and reduced image contrast on D- and E-speed films. As shown by increased half-value layers for aluminum, titanium, and copper and by pulse-height analyses of beam spectra, niobium increased average beam energy by 6% to 19%. Despite the benefits of adding niobium on patient dose reduction and on narrowing the beams' energy spectra, the beam can be overhardened. Adding niobium, therefore, strikes the best balance between radiation dose reduction and beam attenuation, with its risks of increased exposure times, motion blur, and diminished image contrast, when it is used at modest thicknesses (30 μm) and at lower kVp (70) settings. © 1995 Mosby-Year Book, Inc.

Effects of contrast material on computed tomographic measurements of lung volumes in patients with acute lung injury

Background. Intravenous injection of contrast material is routinely performed in order to differentiate nonaerated lung parenchyma from pleural effusion in critically ill patients undergoing thoracic computed tomography (CT). The aim of the present study was to evaluate the effects of contrast material on CT measurement of lung volumes in 14 patients with acute lung injury. Method. A spiral thoracic CT scan, consisting of contiguous axial sections of 10 mm thickness, was performed from the apex to the diaphragm at end-expiration both before and 30 s (group 1; n=7) or 15 min (group 2; n=7) after injection of 80 ml contrast material. Volumes of gas and tissue, and volumic distribution of CT attenuations were measured before and after injection using specially designed software (Lungview®; Institut National des Télécommunications, Evry, France). The maximal artifactual increase in lung tissue resulting from a hypothetical leakage within the lung of the 80 ml contrast material was calculated. Results. Injection of contrast material significantly increased the apparent volume of lung tissue by 83 ± 57 ml in group 1 and 102 ± 80 ml in group 2, whereas the corresponding maximal artifactual increases in lung tissue were 42 ± 52 ml and 31 ± 18 ml. Conclusion. Because systematic injection of contrast material increases the amount of extravascular lung water in patients with acute lung injury, it seems prudent to avoid this procedure in critically ill patients undergoing a thoracic CT scan and to reserve its use for specific indications.

Background interference on the color of dental composite materials with different thickness by digital contrast

In this work the color dependence of resin composites with the background color was evaluated. The objective was to measure since what thickness the color of the sample stops being influenced by the color of the background over which the resin is placed and the methodology used in experiment was based in analyzing the contrast of digital images of the sample over a black background. The results shown that since 0.8 mm the images contrast becomes almost constant; it prove that since this thickness the color of resin composite depends on the optical resin properties only. The experiment was repeated under three conditions of luminosity to evaluate the influence of it on the image contrast and the results obtained were identical.

Phonological remediation program in students with developmental dyslexia

Background: program for phonological remediation in developmental dyslexia. Aim: to verify the efficacy of a program for phonological remediation in students with developmental dyslexia. Specific goals of this study involved the comparison of the linguistic-cognitive performance of students with developmental dyslexia with that of students considered good readers; to compare the results obtained in pre and post-testing situations of students with dyslexia who were and were not submitted to the program; and to compare the results obtained with the phonological remediation program in students with developmental dyslexia to those obtained in good readers. Method: participants of this study were 24 students who were divided as follows: Group I (GI) was divided in two other groups - Gle with 6 students with developmental dyslexia who were submitted to the program; and Glc with 6 students with developmental dyslexia who were not submitted to the program; Group II (GII) was also divided in two other groups - GIIe with 6 good readers who were submitted to the program, and GIIc with 6 good readers who were not submitted to the program. The phonological remediation program (Gonzalez & Rosquete, 2002) was developed in three stages: pre-testing, training and post-testing. Results: results indicate that GI presented a lower performance in phonological skills, reading and writing when compared to GII in the pre-testing situation. However, GIe presented a similar performance to that of GII in the post-testing situation, indicating the effectiveness of the phonological remediation program in students with developmental dyslexia. Conclusion: this study made evident the effectiveness of the phonological remediation program in students with developmental dyslexia.

Technique to combine images produced by different propagation modes of guided waves for damage detection and contrast improvement in plate-like structures

This paper describes an image compounding technique based on the use of different apodization functions, the evaluation of the signals phases and information from the interaction of different propagation modes of Lamb waves with defects for enhanced damage detection, resolution and contrast. A 16 elements linear array is attached to a 1 mm thickness isotropic aluminum plate with artificial defects. The array can excite the fundamental A0 and S0 modes at the frequencies of 100 kHz and 360 kHz, respectively. For each mode two synthetic aperture (SA) images with uniform and Blackman apodization and one image of Coherence Factor Map (CFM) are obtained. The specific interaction between each propagation mode and the defects and the characteristics of acoustic radiation patterns due to different apodization functions result in images with different resolution and contrast. From the phase information one of the SA images is selected at each pixel to compound the final image. The SA images are multiplied by the CFM image to improve contrast and for the dispersive A0 mode it is used a technique for dispersion compensation. There is a contrast improvement of 47.5 dB, reducing the dead zone and improving resolution and damage detection. © 2012 IEEE.

Fruit color and contrast in seasonal habitats - a case study from a cerrado savanna

Communication contributes to mediate the interactions between plants and the animals that disperse their genes. As yet, seasonal patterns in plant-animal communication are unknown, even though many habitats display pronounced seasonality e.g. when leaves senescence. We thus hypothesized that the contrast between fruit displays and their background vary throughout the year in a seasonal habitat. If this variation is adaptive, we predicted higher contrasts between fruits and foliage during the fruiting season in a cerrado-savanna vegetation, southeastern Brazil. Based on a six-year data base of fruit ripening and a one-year data set of fruit biomass, we used reflectance measurements and contrast analysis to show that fruits with distinct colors differed in the beginning of ripening and the peak of fruit biomass. Black, and particularly red fruits, that have a high contrast against the leaf background, were highly seasonal, peaking in the wet season. Multicolored and yellow fruits were less seasonal, not limited to one season, with a bimodal pattern for yellow ones, represented by two peaks, one in each season. We further supported the hypothesis that seasonal changes in fruit contrasts can be adaptive because fruits contrasted more strongly against their own foliage in the wet season, when most fruits are ripe. Hence, the seasonal variation in fruit colors observed in the cerrado-savanna may be, at least partly, explicable as an adaptation to ensure high conspicuousness to seed dispersers. © 2013 The Authors.

Mercury toxicity in the Amazon: contrast sensitivity and color discrimination of subjects exposed to mercury

We measured visual performance in achromatic and chromatic spatial tasks of mercury-exposed subjects and compared the results with norms obtained from healthy individuals of similar age. Data were obtained for a group of 28 mercury-exposed subjects, comprising 20 Amazonian gold miners, 2 inhabitants of Amazonian riverside communities, and 6 laboratory technicians, who asked for medical care. Statistical norms were generated by testing healthy control subjects divided into three age groups. The performance of a substantial proportion of the mercury-exposed subjects was below the norms in all of these tasks. Eleven of 20 subjects (55%) performed below the norms in the achromatic contrast sensitivity task. The mercury-exposed subjects also had lower red-green contrast sensitivity deficits at all tested spatial frequencies (9/11 subjects; 81%). Three gold miners and 1 riverine (4/19 subjects, 21%) performed worse than normal subjects making more mistakes in the color arrangement test. Five of 10 subjects tested (50%), comprising 2 gold miners, 2 technicians, and 1 riverine, performed worse than normal in the color discrimination test, having areas of one or more MacAdam ellipse larger than normal subjects and high color discrimination thresholds at least in one color locus. These data indicate that psychophysical assessment can be used to quantify the degree of visual impairment of mercury-exposed subjects. They also suggest that some spatial tests such as the measurement of red-green chromatic contrast are sufficiently sensitive to detect visual dysfunction caused by mercury toxicity.

Contrast sensitivity of pattern transient VEP components: contribution from M and P pathways

The purpose of this study was to compare contrast sensitivity estimated from transient visual evoked potentials (VEPs) elicited by achromatic pattern-reversal and pattern-onset/offset modes. The stimuli were 2-cpd, achromatic horizontal gratings presented either as a 1 Hz pattern reversal or a 300 ms onset/700 ms offset stimulus. Contrast thresholds were estimated by linear regression to amplitudes of VEP components vs. the logarithm of the stimulus contrasts, and these regressions were extrapolated to the zero amplitude level. Contrast sensitivity was defined as the inverse of contrast threshold. For pattern reversal, the relation between the P100 amplitude and log of the stimulus contrast was best described by two separate linear regressions. For the N135 component, a single straight line was sufficient. In the case of pattern onset/offset for both the C1 and C2 components, single straight lines described their amplitude vs. log contrast relations in the medium-to-low contrast range. Some saturation was observed for C2 components. The contrast sensitivity estimated from the low-contrast limb of the P100, from the N135, and from the C2 were all similar but higher than those obtained from the high-contrast limb of the P100 and C1 data, which were also similar to each other. With 2 cpd stimuli, a mechanism possibly driven by the M pathway appeared to contribute to the P100 component at medium-to-low contrasts and to the N135 and C2 components at all contrast levels, whereas another mechanism, possibly driven by the P and M pathways, appeared to contribute to the P100 component at high contrast and C1 component at all contrast levels.

Chromatic spatial contrast sensitivity estimated by visual evoked cortical potential and psychophysics

The purpose of the present study was to measure contrast sensitivity to equiluminant gratings using steady-state visual evoked cortical potential (ssVECP) and psychophysics. Six healthy volunteers were evaluated with ssVECPs and psychophysics. The visual stimuli were red-green or blue-yellow horizontal sinusoidal gratings, 5^° × 5^°, 34.3 cd/m2 mean luminance, presented at 6 Hz. Eight spatial frequencies from 0.2 to 8 cpd were used, each presented at 8 contrast levels. Contrast threshold was obtained by extrapolating second harmonic amplitude values to zero. Psychophysical contrast thresholds were measured using stimuli at 6 Hz and static presentation. Contrast sensitivity was calculated as the inverse function of the pooled cone contrast threshold. ssVECP and both psychophysical contrast sensitivity functions (CSFs) were low-pass functions for red-green gratings. For electrophysiology, the highest contrast sensitivity values were found at 0.4 cpd (1.95 ± 0.15). ssVECP CSF was similar to dynamic psychophysical CSF, while static CSF had higher values ranging from 0.4 to 6 cpd (P < 0.05, ANOVA). Blue-yellow chromatic functions showed no specific tuning shape; however, at high spatial frequencies the evoked potentials showed higher contrast sensitivity than the psychophysical methods (P < 0.05, ANOVA). Evoked potentials can be used reliably to evaluate chromatic red-green CSFs in agreement with psychophysical thresholds, mainly if the same temporal properties are applied to the stimulus. For blue-yellow CSF, correlation between electrophysiology and psychophysics was poor at high spatial frequency, possibly due to a greater effect of chromatic aberration on this kind of stimulus.

Comparative neurophysiology of spatial luminance contrast sensitivity

The luminance contrast sensitivity function has been investigated using behavioral and electrophysiological methods in many vertebrate species. Some features are conserved across species as a shape of the function, but other features, such as the contrast sensitivity peak value, spatial frequency contrast sensitivity peak, and visual acuity have changed. Here, we review contrast sensitivity across different classes of vertebrates, with an emphasis on the frequency contrast sensitivity peak and visual acuity. We also correlate the data obtained from the literature to test the power of the association between visual acuity and the spatial frequency of the contrast sensitivity function peak.

Aquisição fonológica de fricativas por crianças com transtorno fonológico: uma investigação acústica

Pós-graduação em Estudos Linguísticos - IBILCE