Predicting retrosynthetic pathways using transformer-based models and a hyper-graph exploration strategy

We present an extension of our Molecular Transformer model combined with a hyper-graph exploration strategy for automatic retrosynthesis route planning without human intervention. The single-step retrosynthetic model sets a new state of the art for predicting reactants as well as reagents, solvents and catalysts for each retrosynthetic step. We introduce four metrics (coverage, class diversity, round-trip accuracy and Jensen–Shannon divergence) to evaluate the single-step retrosynthetic models, using the forward prediction and a reaction classification model always based on the transformer architecture. The hypergraph is constructed on the fly, and the nodes are filtered and further expanded based on a Bayesian-like probability. We critically assessed the end-to-end framework with several retrosynthesis examples from literature and academic exams. Overall, the frameworks have an excellent performance with few weaknesses related to the training data. The use of the introduced metrics opens up the possibility to optimize entire retrosynthetic frameworks by focusing on the performance of the single-step model only.

We present an extension of our Molecular Transformer model combined with a hyper-graph exploration strategy for automatic retrosynthesis route planning without human intervention.     

Perception of static and dynamic acoustic cues to place of articulation in initial stop consonants

Two recent accounts of the acoustic cues which specify place of articulation in syllable-initial stop consonants claim that they are located in the initial portions of the CV waveform and are context-free. Stevens and Blumstein [J. Acoust. Soc. Am. 64, 1358-1368 (1978)] have described the perceptually relevant spectral properties of these cues as static, while Kewley-Port [J. Acoust. Soc. Am. 73, 322-335 (1983)] describes these cues as dynamic. Three perceptual experiments were conducted to test predictions derived from these accounts. Experiment 1 confirmed that acoustic cues for place of articulation are located in the initial 20-40 ms of natural stop-vowel syllables. Next, short synthetic CV's modeled after natural syllables were generated using either a digital, parallel-resonance synthesizer in experiment 2 or linear prediction synthesis in experiment 3. One set of synthetic stimuli preserved the static spectral properties proposed by Stevens and Blumstein. Another set of synthetic stimuli preserved the dynamic properties suggested by Kewley-Port. Listeners in both experiments identified place of articulation significantly better from stimuli which preserved dynamic acoustic properties than from those based on static onset spectra. Evidently, the dynamic structure of the initial stop-vowel articulatory gesture can be preserved in context-free acoustic cues which listeners use to identify place of articulation.     

X-ray determination of the mean amplitudes of vibration and debye temperatures of some rare earth monochalcogenides

The x-ray diffraction intensities of Bragg reflections have been measured at room temperature for thulium selenide, samarium sulphide, samarium selenide and samarium telluride. On the basis of a common amplitude approximation, the Debye-Waller factor, the mean amplitude of vibration and the Debye temperature have been evaluated. The values of the Debye temperatures and mean amplitudes of vibration are 176±16°K, 0·185 ± 0·017 Å (TmSe), 155 ± 7°K, 0·244 ± 0·012 Å (SmS), 153 ± 14°K, 0·221 ± 0·020 Å (SmSe) and 151 ± 20°K, 0·204 ± 0·027 Å (SmTe).     

Effects of word frequency, contextual diversity, and semantic distinctiveness on spoken word recognition

The relative abilities of word frequency, contextual diversity, and semantic distinctiveness to predict accuracy of spoken word recognition in noise were compared using two data sets. Word frequency is the number of times a word appears in a corpus of text. Contextual diversity is the number of different documents in which the word appears in that corpus. Semantic distinctiveness takes into account the number of different semantic contexts in which the word appears. Semantic distinctiveness and contextual diversity were both able to explain variance above and beyond that explained by word frequency, which by itself explained little unique variance.     

Auditory-visual speech perception and synchrony detection for speech and nonspeech signals

Previous research has identified a "synchrony window" of several hundred milliseconds over which auditory-visual (AV) asynchronies are not reliably perceived. Individual variability in the size of this AV synchrony window has been linked with variability in AV speech perception measures, but it was not clear whether AV speech perception measures are related to synchrony detection for speech only or for both speech and nonspeech signals. An experiment was conducted to investigate the relationship between measures of AV speech perception and AV synchrony detection for speech and nonspeech signals. Variability in AV synchrony detection for both speech and nonspeech signals was found to be related to variability in measures of auditory-only (A-only) and AV speech perception, suggesting that temporal processing for both speech and nonspeech signals must be taken into account in explaining variability in A-only and multisensory speech perception.     

Effects of noise on speech production: acoustic and perceptual analyses

Acoustical analyses were carried out on a set of utterances produced by two male speakers talking in quiet and in 80, 90, and 100 dB SPL of masking noise. In addition to replicating previous studies demonstrating increases in amplitude, duration, and vocal pitch while talking in noise, these analyses also found reliable differences in the formant frequencies and short-term spectra of vowels. Perceptual experiments were also conducted to assess the intelligibility of utterances produced in quiet and in noise when they were presented at equal S/N ratios for identification. In each experiment, utterances originally produced in noise were found to be more intelligible than utterances produced in the quiet. The results of the acoustic analyses showed clear and consistent differences in the acoustic-phonetic characteristics of speech produced in quiet versus noisy environments. Moreover, these accounts differences produced reliable effects on intelligibility. The findings are discussed in terms of: (1) the nature of the acoustic changes that taken place when speakers produce speech under adverse conditions such as noise, psychological stress, or high cognitive load: (2) the role of training and feedback in controlling and modifying a talker's speech to improve performance of current speech recognizers; and (3) the development of robust algorithms for recognition of speech in noise.     

Identification and discrimination of bilingual talkers across languages

This study investigated the extent to which language familiarity affects the perception of the indexical properties of speech by testing listeners' identification and discrimination of bilingual talkers across two different languages. In one experiment, listeners were trained to identify bilingual talkers speaking in only one language and were then tested on their ability to identify the same talkers speaking in another language. In the second experiment, listeners discriminated between bilingual talkers across languages in an AX discrimination paradigm. The results of these experiments indicate that there is sufficient language-independent indexical information in speech for listeners to generalize knowledge of talkers' voices across languages and to successfully discriminate between bilingual talkers regardless of the language they are speaking. However, the results of these studies also revealed that listeners do not solely rely on language-independent information when performing these tasks. Listeners use language-dependent indexical cues to identify talkers who are speaking a familiar language. Moreover, the tendency to perceive two talkers as the "same" or "different" depends on whether the talkers are speaking in the same language. The combined results of these experiments thus suggest that indexical processing relies on both language-dependent and language-independent information in the speech signal.