Yu-Tsai Wang

Observation of a topological crystalline insulator phase and topological phase transition in Pb 1− x Sn x Te

A topological insulator protected by time-reversal symmetry is realized via spinorbit interaction driven band inversion. The topological phase in the Bi1−xSbx system is due to an odd number of band inversions. A related spin-orbit system, the Pb1−xSnxTe, has long been known to contain an even number of inversions based on band theory. Here we experimentally investigate the possibility of a mirror symmetry protected topological crystalline insulator phase in the Pb1−xSnxTe class of materials which has been theoretically predicted to exist in its end compound SnTe. Our experimental results show that at a finite-Pb composition above the topological inversion phase transition, the surface exhibits even number of spin-polarized Dirac cone states revealing mirror-protected topological order distinct from that observed in Bi1−xSbx. Our observation of the spin-polarized Dirac surface states in the inverted Pb1−xSnxTe and their absence in the non-inverted compounds related via a topological phase transition provide the experimental groundwork for opening the research on novel topological order in quantum devices.A topological insulator protected by time-reversal symmetry is realized via spin-orbit interaction-driven band inversion. The topological phase in the Bi(1-x)Sb(x) system is due to an odd number of band inversions. A related spin-orbit system, the Pb(1-x)Sn(x)Te, has long been known to contain an even number of inversions based on band theory. Here we experimentally investigate the possibility of a mirror symmetry-protected topological crystalline insulator phase in the Pb(1-x)Sn(x)Te class of materials that has been theoretically predicted to exist in its end compound SnTe. Our experimental results show that at a finite Pb composition above the topological inversion phase transition, the surface exhibits even number of spin-polarized Dirac cone states revealing mirror-protected topological order distinct from that observed in Bi(1-x)Sb(x). Our observation of the spin-polarized Dirac surface states in the inverted Pb(1-x)Sn(x)Te and their absence in the non-inverted compounds related via a topological phase transition provide the experimental groundwork for opening the research on novel topological order in quantum devices.

Tongue-surface movement patterns during speech and swallowing.

The tongue has been frequently characterized as being composed of several functionally independent articulators. The question of functional regionality within the tongue was examined by quantifying the strength of coupling among four different tongue locations across a large number of consonantal contexts and participants. Tongue behavior during swallowing was also described. Vertical displacements of pellets affixed to the tongue were extracted from the x-ray microbeam database. Forty-six participants recited 20 vowel-consonant-vowel (VCV) combinations and swallowed 10 ccs of water. Tongue-surface movement patterns were quantitatively described by computing the covariance between the vertical time-histories of all possible pellet pairs. Phonemic differentiation in vertical tongue motions was observed as coupling varied predictably across pellet pairs with place of articulation. Moreover, tongue displacements for speech and swallowing clustered into distinct groups based on their coupling profiles. Functional independence of anterior tongue regions was evidenced by a wide range of movement coupling relations between anterior tongue pellets. The strengths and weaknesses of the covariance-based analysis for characterizing tongue movement are considered.

Breath Group Analysis for Reading and Spontaneous Speech in Healthy Adults

Aims: The breath group can serve as a functional unit to define temporal and fundamental frequency (f₀) features in continuous speech. These features of the breath group are determined by the physiologic, linguistic, and cognitive demands of communication. Reading and spontaneous speech are two speaking tasks that vary in these demands and are commonly used to evaluate speech performance for research and clinical applications. The purpose of this study is to examine differences between reading and spontaneous speech in the temporal and f₀ aspects of their breath groups. Methods: Sixteen participants read two passages and answered six questions while wearing a circumferentially vented mask connected to a pneumotach. The aerodynamic signal was used to identify inspiratory locations. The audio signal was used to analyze task differences in breath group structure, including temporal and f₀ components. Results: The main findings were that spontaneous speech task exhibited significantly more grammatically inappropriate breath group locations and longer breath group duration than did the passage reading task. Conclusion: The task differences in the percentage of grammatically inadequate breath group locations and in breath group duration for healthy adult speakers partly explain the differences in cognitive-linguistic load between the passage reading and spontaneous speech.

Accuracy of perceptually based and acoustically based inspiratory loci in reading

Investigations of speech often involve the identification of inspiratory loci in continuous recordings of speech. The present study investigates the accuracy of perceptually determined and acoustically determined inspiratory loci. While wearing a circumferentially vented mask connected to a pneumotach, 16 participants read two passages. The perceptually determined and acoustically determined inspiratory loci were compared with the actual loci of inspiration, which were determined aerodynamically. The results showed that (1) agreement across all three judges was the most accurate of the approaches considered here for detecting inspiratory loci based on listening; (2) the most accurate pause duration threshold for detecting inspiratory loci was 250 msec; and (3) the perceptually based breath-group determination was more accurate than the acoustically based determination of pause duration. Inconsistencies among perceptually determined, acoustically determined, and aerodynamically determined inspiratory loci are not negligible and, therefore, need to be considered when researchers design experiments on breath groups in speech.

Respiratory Changes during Reading in Mandarin-Speaking Adolescents with Prelingual Hearing Impairment

Objective: Most people with severe to profound hearing impairment (SHI) exhibit speech breathing changes, but little is known about the breath group (BG) structure for this population. The purposes of this study were to investigate, compared to speakers with normal hearing, if Mandarin-speaking adolescents with prelingual SHI take inspirations more often at syntactically inappropriate positions and exhibit a difference in the temporal BG characteristics. Patients and Methods: Forty participants, 20 speakers with prelingual SHI and 20 normal-hearing controls matched for age, sex and education level were recruited. While wearing a circumferentially vented mask connected to a pneumotachograph, the subjects read three passages. The airflow signal was used to locate inspiratory loci in the speech samples. Temporal parameters of BG structure were derived from the acoustic signal. Results: The SHI group, compared to the control group, had significantly (1) more inspiratory loci at inappropriate and minor syntactic boundaries; (2) fewer syllables per BG, slower speaking rate, longer inter-BG pauses, and longer noninspiratory pauses, but comparable inspiratory duration, expiration duration, and BG duration. Conclusion: The slower speaking rate within BGs and longer inter-BG pauses mainly account for the respiratory changes in Mandarin-speaking adolescents with prelingual SHI.

Corrigendum: Observation of a topological crystalline insulator phase and topological phase transition in Pb1-xSnxTe.

Nature Communications 3: Article number: 1192 (2012); Published: 13 November 2012; Updated: 4 August 2016. In Fig. 2a and d of this Article, a uniform background subtraction was applied to the ARPES low-energy electronic structure measurements. In Fig. 2d, this background subtraction unintentionallywas only applied to the central part of the figure.

Acoustic validation of the analysis of diadochokinesis in normal speech using the motor speech profile program

The purpose of this study is to evaluate the suitability, reliability, and concurrent validity of the analysis of diadochochinesis (DDK) in normal speech using a computer program, Diadochokinetic Rate Analysis (DRA) in the KayPENTAX Motor Speech Profile. Fifteen healthy participants were recorded at UW-Madison as they repeated various syllables as quickly and steadily as possible. The DDK samples were executed by the DRA protocol to generate immediate quantitative information at dierent thresholds and were also hand-measured. When the lowest peak intensity during consonant-vowel syllables is lower than the highest peak intensity during intersyllable pauses, the DRA output is incorrect and the DDK sample is defined as nonexecutable. Analyses were based on the percentage of nonexecutable DDK samples and the comparisons of the results between repeated analyses at dierent thresholds and between automatic and manual measuring methods. Results: (1) One-ninth of the DDK samples was nonexecutable; (2) when the protocol was executable, the reliability at dierent thresholds and validity between dierent measuring methods were both satisfactory; and (3) the temporal variation between dierent measuring methods were larger than the intensity variation. Implications of the findings will be discussed in terms of the application of the DRA to general clinical purposes.

Tongue surface dynamics during speech and swallowing

This investigation characterizes tongue surface dynamics that underlie phonemic variation and that distinguish speech from swallowing. Vertical displacements of pellets affixed to the tongue were extracted from the x‐ray microbeam database [Westbury, J. X‐ray Microbeam Speech Production Database Users Handbook, Version 1 (1994)], which contains articulatory kinematic data from 57 typical speakers. Participants recited 21 vowel–consonant–vowel (VCV) combinations, read the Grandfather Passage, and swallowed 10 cc of water. Consonantal context was manipulated in the VCV utterances as a means to describe the range of tongue dynamics produced during speech. For each task, tongue dynamics was quantified by performing zero‐lag cross correlations on selected pellet pairs. A coupling index was then computed by scaling the derived coefficients by a multiplier that reflected the amplitude of each displacement signal. A wide range of movement coupling among tongue pellets was observed across tasks. Phonemic different...