Effects of type of emission and masking sound, and their spatial correspondence, on blind and sighted people's ability to echolocate.

Ambient sound can mask acoustic signals. The current study addressed how echolocation in people is affected by masking sound, and the role played by type of sound and spatial (i.e. binaural) similarity. We also investigated the role played by blindness and long-term experience with echolocation, by testing echolocation experts, as well as blind and sighted people new to echolocation. Results were obtained in two echolocation tasks where participants listened to binaural recordings of echolocation and masking sounds, and either localized echoes in azimuth or discriminated echo audibility. Echolocation and masking sounds could be either clicks or broad band noise. An adaptive staircase method was used to adjust signal-to-noise ratios (SNRs) based on participants' responses. When target and masker had the same binaural cues (i.e. both were monoaural sounds), people performed better (i.e. had lower SNRs) when target and masker used different types of sound (e.g. clicks in noise-masker or noise in clicks-masker), as compared to when target and masker used the same type of sound (e.g. clicks in click-, or noise in noise-masker). A very different pattern of results was observed when masker and target differed in their binaural cues, in which case people always performed better when clicks were the masker, regardless of type of emission used. Further, direct comparison between conditions with and without binaural difference revealed binaural release from masking only when clicks were used as emissions and masker, but not otherwise (i.e. when noise was used as masker or emission). This suggests that echolocation with clicks or noise may differ in their sensitivity to binaural cues. We observed the same pattern of results for echolocation experts, and blind and sighted people new to echolocation, suggesting a limited role played by long-term experience or blindness. In addition to generating novel predictions for future work, the findings also inform instruction in echolocation for people who are blind or sighted.

Increased emission intensity can compensate for the presence of noise in human click-based echolocation.

Echolocating bats adapt their emissions to succeed in noisy environments. In the present study we investigated if echolocating humans can detect a sound-reflecting surface in the presence of noise and if intensity of echolocation emissions (i.e. clicks) changes in a systematic pattern. We tested people who were blind and had experience in echolocation, as well as blind and sighted people who had no experience in echolocation prior to the study. We used an echo-detection paradigm where participants listened to binaural recordings of echolocation sounds (i.e. they did not make their own click emissions), and where intensity of emissions and echoes changed adaptively based on participant performance (intensity of echoes was yoked to intensity of emissions). We found that emission intensity had to systematically increase to compensate for weaker echoes relative to background noise. In fact, emission intensity increased so that spectral power of echoes exceeded spectral power of noise by 12 dB in 4-kHz and 5-kHz frequency bands. The effects were the same across all participant groups, suggesting that this effect occurs independently of long-time experience with echolocation. Our findings demonstrate for the first time that people can echolocate in the presence of noise and suggest that one potential strategy to deal with noise is to increase emission intensity to maintain signal-to-noise ratio of certain spectral components of the echoes.

Influence of surfactant supplementation and maceration on the feeding value of rice straw in growing-finishing diets for Holstein steers.

Two trials were conducted to evaluate the interaction of the maceration process and surfactant (Tween 80) supplementation on feeding value of rice straw. Treatments were steam-flaked, corn-based diets containing 14% forage (DM basis), which was 1) Sudangrass hay; 2) ground rice straw; 3) ground rice straw plus 0.22% Tween 80; 4) macerated rice straw; and 5) macerated rice straw plus 0.22% Tween 80. In the maceration process, rice straw was passed through 2 sequentially placed pairs of corrugated rolls set at zero tolerance under a ram pressure of 62,050 millibars, similar to a conventional grain roller mill, except that the opposing rolls operated at different speeds (12 and 14 rpm, respectively). Sudangrass hay and rice straw (native and macerated) were ground through a 2.6-cm screen before incorporation into complete mixed diets. In trial 1, 125 Holstein steers (292 +/- 1.7 kg of BW) were used in a 188-d evaluation of the treatment effects on growth performance and carcass characteristics. In trial 2, 5 Holstein steers (224 +/- 3.5 kg of BW) with cannulas in the rumen and proximal duodenum were used in a 5 x 5 Latin square design to evaluate the treatment effects on digestion. There were no interactions between maceration and surfactant on growth or carcass characteristics. Tween 80 did not influence the feeding value of rice straw. Compared with grinding alone, maceration of rice straw increased the carcass-adjusted ADG (6%, P < 0.10), G:F (6%, P < 0.05), and dietary NE (5%, P < 0.05); DMI was similar across treatments. Assuming NE(m) and NE(g) of Sudangrass hay are 1.18 and 0.62 Mcal/kg, the NE(m) and NE(g) were 0.61 and 0.13 Mcal/kg for ground rice straw and 1.21 and 0.65 Mcal/kg for macerated rice straw. There were no treatment interactions on characteristics of digestion. Tween 80 did not influence ruminal or total tract digestion of OM, starch, NDF, or N. Compared with grinding alone, maceration of rice straw increased ruminal digestion of OM (7.7%, P < 0.10) and NDF (30.8%, P < 0.05), and total tract digestion of OM (2.3%, P < 0.10), NDF (21.1%, P < 0.01), and N (3.7%, P < 0.05). Total tract digestion of OM, NDF, starch, and N for the Sudangrass diet corresponded closely with that of the macerated rice straw diets. Maceration increases the feeding value of rice straw to a level similar to that of good-quality (flag stage of maturity) Sudangrass hay, which is attributable to increased OM and NDF digestion. Effects of surfactant supplementation on growth performance and digestion are not appreciable.

[Factors associated to the visiting time in patients with ischaemic cerebrovascular disease]. / Factores asociados al tiempo de consulta en pacientes con enfermedad cerebrovascular isquémica.

INTRODUCTION: The high prevalence of cerebrovascular disease in underdeveloped countries has made it a public health issue. Establishing therapy within the first three hours in the case of patients with cerebrovascular disease has proved to have beneficial effects on the patient. AIM: To identify the factors associated with the time taken to visit the hospital emergency department by patients with ischaemic cerebrovascular disease in the population of Colombia. PATIENTS AND METHODS: We conducted a cross-sectional analytical study that included patients over 18 years old who had been clinically diagnosed as having an acute ischaemic cerebrovascular disease. The time between onset of symptoms and admission to the emergency department was estimated and then related to sociodemographic and cultural factors and the severity of the clinical features. RESULTS: The mean time taken to visit hospital was 17 hours and 48 minutes (standard deviation: 24 hours and 12 minutes). In 22.8% of cases the patient was admitted within the first three hours. Patients who were covered by the subsidised health care system and came from low socioeconomic classes, together with those from rural areas took longer to visit (p < 0.005). The values on the United States Institute of Health scale did not have any relation to visiting times. CONCLUSIONS: The time that elapses between the presentation of the cerebrovascular disease and visiting the emergency department in the Colombian population is high, especially among the population with lower levels of income and schooling. There is a need to implement models of education targeted towards the community and focused on the early identification of signs, symptoms and impact of cerebrovascular disease, as well as to set up a system of health care that prevents delays by coordinating resources both inside and outside hospitals.

[Musical perception and cognitive functions. Is there such a thing as the Mozart effect?]. / Percepción musical y funciones cognitivas. Existe el efecto Mozart?

INTRODUCTION: Throughout the second half of the 20th century important advances were made in the study of neurobiology related to the processing of music, the differences and similarities between the neural pathways involved in language and in music, the role played by each hemisphere in recognising these stimuli, and the effects that exposure to certain specific pieces of music could have on the cognitive functions. DEVELOPMENT: The objective of this study is to review the literature concerning music and the central nervous system, bearing in mind the above-mentioned aspects. Likewise, we also wanted to analyse the reports referring to the Mozart effect and Tomatis, in addition to those dealing with formal musical education and its effects. The increased capacity to respond in visuospatial-type tasks after exposure to music by Mozart has triggered a commercial boom which makes use of isolated data, while the real extent of the effect remains unknown. CONCLUSIONS: After reviewing the scientific literature on this subject, it was found that the effects of exposure to music by Mozart (the 'Mozart effect') when they actually occurred, were limited to a specific skill that did not last for more than a few minutes. Formal musical education, on the other hand, shows more permanent positive effects but which can be attributed to the individual attention the pupil receives and to the stimulation in basic skills for general learning.

An accuracy evaluation of four removable die systems.

STATEMENT OF PROBLEM: The advent of implant dentistry has redefined the need for accuracy of working cast models. Die stone expansion and errors introduced by removable die casts may exceed the accuracy required for the passive fit of implant prostheses. PURPOSE: Several removable die systems claim improved accuracy because of their design and/or technical advancements. This study evaluated the 3-dimensional accuracy of 4 removable die systems. All 4 systems tested use either 1 or 2 pins as the repositioning device. MATERIAL AND METHODS: Four removable die systems were evaluated (Belle de St. Claire, Pindex, DVA, and conventional brass dowel system). Master model impressions were made with polyvinyl siloxane material and were later cast with type IV die stone material. Comparative dimensional analysis between the master model and the solid and sectioned casts was made by placing the cast in a standardized position and fabricating an individual custom base for each cast. Landmarks were measured with a traveling microscope, and by mathematically rotating the casts. Discrepancies beyond that of stone expansion or residual stress release at the time of die separation were due to the inability to precisely reposition the removable die of the sectioned cast. Data were analyzed with multivariate analysis of variance and paired t tests at alpha = .05 (n = 10). RESULTS: Significant differences were found among die systems tested (P = .005). When sectioned dies were compared with the master model, the accuracy of all 4 die systems was within 0.055 mm of the master model. Once sectioned, the Pindex system had the least linear expansion in the y dimension, and the brass dowel system demonstrated the least reseating discrepancy in the z (occlusogingival) dimension. CONCLUSIONS: All 4 die systems provided a similar degree of dimensional accuracy, although Pindex showed the least horizontal movement and the brass dowel system produced the least occlusogingival reseating discrepancy.

A method for true coordinate three-dimensional measurement of casts using a measuring microscope.

Exact 3-dimensional measurements are more useful for researchers and clinicians than are relative distance measurements. Through the use of a measuring microscope and a personal computer, the technique presented in this article provides meaningful and accurate (0.005 mm) 3-dimensional measurements of casts in true coordinates (x, y, z). By fabricating the master cast with reference landmarks, leveling the casts before measurement, removing the cast between repeat measures, and mathematically rotating the data points, this technique places all the landmarks in a standardized reference plane that allows for the comparison of dimensional changes between different casts.