Free submonoids and minimal ω-generators of Rω

Let A be an alphabet and let R be a language in A+. An (¿-generator of -R" is a language G such that G" = R". The language Stab(-R") = {u G A* : ttiZ" Ç R"} is a submonoid of A*. We give results concerning the wgenerators for the case when Stab(Ru ) is a free submonoid which are not available in the general case. In particular, we prove that every ((»-generator of 22" contains at least one minimal w-generator of R". Furthermore these minimal w-generators are codes. We also characterize the w-languagea having only finite languages as minimal u-generators. Finally, we characterize the w- languages »-generated by finite prefix codes

Developmental changes in sound localization precision under conditions of the precedence effect.

The ability to give perceptual priority to an original sound source and ignore later-arriving echoes of that sound is termed the law of the first wave-front , or the precedence effect (PE). Little attention has been paid to the influence that echoes exert on localization accuracy for the leading sound. The present study investigated localization precision of children and adults in the presence of a simulated echo, using the minimal audible angle (MAA) task, which indicates the smallest change in the location of a sound that can be reliably discriminated. Three age groups were tested: 18-months, 5-years, and adults. Each age group was tested with one single-source (SS) stimulus, and two precedence effect (PE) stimuli: LEAD, in which the original sound shifted from midline and the echo remained at midline, and LAG, where the reverse occurred. Subjects were tested using an adaptive, 2-down/1-up, psychophysical algorithm. For all age groups, MAA thresholds were smallest for SS, larger for LEAD and largest for LAG. For all three stimulus conditions, the 18-month-olds\u27 thresholds were significantly larger than those of either 5-year-olds or adults. Five-year-olds\u27 MAA thresholds for SS sounds were very near to those of adults. However, their thresholds for the PE stimuli were significantly higher than those of adults\u27, and closer to those of 18-month-olds. When a lagging sound is inaudible as a separate auditory event, the auditory system presumably treats the leading and lagging sound as components of the same auditory percept, and uses both signals to compute the position of the sound source. The leading sound, which signals the onset of an auditory event, is assigned perceptual dominance thereby diminishing the nervous system\u27s interaural sensitivity for the later-arriving echo. This and related work has raised important questions concerning the neural mechanisms involved in spatial hearing in adults and children, especially those aspects which involve an active suppression of superfluous signals

Heat Transfer Mechanisms in Porous Materials and Contemporary Problems in Thermophysical Properties Investigations: Analyses and Solutions

This article is an overview of the topical problems in the investigation of thermophysical properties and the development of a database for porous materials. Determination of both apparent/measured and true thermophysical properties is discussed taking into account combined heat and mass transfer, latent heat effects during chemical and physical transformations, as well as structural changes. The approaches to the solution of these problems are demonstrated for a number of different classes of materials: Industrial refractories, ceramics, highly porous insulation; Moist materials and materials undergoing phase, chemical and structural transformations; Materials semitransparent for heat radiation. The approaches being used in the development of a thermophysical properties database consist in a combination of theoretical and experimental methods. The analysis, generalization, and extrapolation of available reference data can be conducted based on the models for classical (conduction, heat radiation, gas convection) and additional (novel) mechanisms and processes affecting the apparent thermophysical properties. The novel heat transfer mechanisms include: Heterogeneous heat and mass transfer processes occurring in pores existing at grain boundaries and in cracks, in particular, surface segregation and diffusion of impurities on pore surfaces and transport of gases produced from chemical reactions, evaporation, and sublimation. Microstructure changes due to non-uniform thermal expansion of particles and grains. These changes are caused by the mismatch of thermal expansion coefficients of different phases in the material and anisotropic thermal expansion of crystals

Using curiosity to counter health information avoidance

Objective: Information that is beneficial for health decision-making is often ignored or actively avoided. Countering information avoidance can increase knowledge of disease risk factors and symptoms, aiding early diagnoses and reducing disease transmission. We examine whether curiosity can be a useful tool in increasing demand for, and engagement with, potentially aversive but useful health information. Methods: Four pre-registered randomized online studies were conducted with 5795 participants recruited from online survey platforms. Curiosity for aversive health information was manipulated by providing a 'curiosity incentive' - identity-related information alongside aversive information - (Study 1), obscuring information (Studies 2 and 3), and eliciting guesses about the information (Studies 2 and 4). Willingness to view four types of aversive health information was elicited: alcohol consumption screening scores (Study 1), colon cancer risk scores (Study 2), cancer risk factors (Study 3), and the sugar content of drinks (Study 4). Results: In Study 1, the curiosity manipulation increased the likelihood that participants viewed information about the riskiness of their drinking. Studies 2 and 3 show that curiosity prompts can counter people's reluctance to learn about and assess their cancer risk. And Study 4 shows that using curiosity prompts to encourage engagement with aversive information (sugar content of drinks) also improves health-related choices (opting for a sugar-free drink alternative). Conclusion: Curiosity prompts provide an effective and simple way to increase engagement with aversive health information.</p

Across-frequency combination of interaural time difference in bilateral cochlear implant listeners

The current study examined how cochlear implant (CI) listeners combine temporally interleaved envelope-ITD information across two sites of stimulation. When two cochlear sites jointly transmit ITD information, one possibility is that CI listeners can extract the most reliable ITD cues available. As a result, ITD sensitivity would be sustained or enhanced compared to single-site stimulation. Alternatively, mutual interference across multiple sites of ITD stimulation could worsen dual-site performance compared to listening to the better of two electrode pairs. Two experiments used direct stimulation to examine how CI users can integrate ITDs across two pairs of electrodes. Experiment 1 tested ITD discrimination for two stimulation sites using 100-Hz sinusoidally modulated 1000-pps-carrier pulse trains. Experiment 2 used the same stimuli ramped with 100 ms windows, as a control condition with minimized onset cues. For all stimuli, performance improved monotonically with increasing modulation depth. Results show that when CI listeners are stimulated with electrode pairs at two cochlear sites, sensitivity to ITDs was similar to that seen when only the electrode pair with better sensitivity was activated. None of the listeners showed a decrement in performance from the worse electrode pair. This could be achieved either by listening to the better electrode pair or by truly integrating the information across cochlear sites

On the Recognition of Families of Graphs with Local Computations

AbstractThis paper is a contribution to understanding the power and the limitations of local computations in graphs. We use local computations to define a notion of graph recognition; our model allows a simulation of automata on words and on trees. We introduce the notion of k-covering to examine limitations of such systems. For example, we prove that the family of series-parallel graphs and the family of planar graphs cannot be recognized by means of local computations

Fulminating herpes simplex hepatitis

Herpes simplex virus (HSV) is a rare cause of acute hepatitis in patients with chronic immunosuppression, including Crohn’s disease. HSV hepatitis has the propensity to cause acute liver failure and death. The presenting signs and symptoms can be nonspecific, thereby causing the diagnosis to go overlooked with inadequate management, leading to a high mortality rate. We report a case of a 31-year-old male on chronic prednisone treatment for Crohn’s disease who unexpectedly died. Subsequently, an autopsy showed HSV hepatitis as the cause of death. Thus, although a rare complication, HSV hepatitis should always be kept in mind as a fatal complication in patients with acute hepatitis and chronic immunosuppression

The Reduction of Vertical Interchannel Crosstalk: The Analysis of Localisation Thresholds for Natural Sound Sources

In subjective listening tests, natural sound sources were presented to subjects as vertically-oriented phantom images from two layers of loudspeakers, ‘height’ and ‘main’. Subjects were required to reduce the amplitude of the height layer until the position of the resultant sound source matched that of the same source presented from the main layer only (the localisation threshold). Delays of 0, 1 and 10 ms were applied to the height layer with respect to the main, with vertical stereophonic and quadraphonic conditions being tested. The results of the study showed that the localisation thresholds obtained were not significantly affected by sound source or presentation method. Instead, the only variable whose effect was significant was interchannel time difference (ICTD). For ICTD of 0 ms, the median threshold was −9.5 dB, which was significantly lower than the −7 dB found for both 1 and 10 ms. The results of the study have implications both for the recording of sound sources for three-dimensional (3D) audio reproduction formats and also for the rendering of 3D images