This paper presents an automatic approach to segment 3-D hand trajectories and transcribe phonemes based on them, as a step towards recognizing American sign language (ASL). We first apply a segmentation algorithm which detects minimal velocity and maximal change of directional angle to segment the hand motion trajectory of naturally signed sentences. This yields oversegmented trajectories, which are further processed by a trained naïve Bayesian detector to identify true segmented points and eliminate false alarms. The above segmentation algorithm yielded 88.5% true segmented points and 11.8% false alarms on unseen ASL sentence samples. These segmentation results were refined by a simple majority voting scheme, and the final segments obtained were used to transcribe phonemes for ASL. This was based on clustering PCA-based features extracted from training sentences. We then trained Hidden Markov Models (HMMs) to recognize the sequence of phonemes in the sentences. On the 25 test sentences containing 157 segments, the average number of errors obtained was 15.6.
SUMMARYAmong the current five Variants of Concern, infections caused by the SARS-CoV-2 B.1.617.2 (Delta) variant are often associated with the greatest severity. Despite recent advances on the molecular basis of elevated pathogenicity using recombinant proteins, architecture of intact Delta virions remains veiled. Moreover, the detailed mechanism of S-mediated membrane fusion remains elusive. Here we report the molecular assembly and fusion snapshots of the authentic Delta variant. Envelope invagination and fusion events were frequently observed. Native structures of pre- and postfusion S were determined up to 4.1-Å resolution. Site-specific glycan analysis revealed increased oligomannose-type glycosylation of native Delta S over that of the Wuhan-Hu-1 S. Based on these findings, we proposed a model for S-mediated membrane fusion and a model for the invagination formation.In BriefCryo-ET of intact SARS-CoV-2 Delta variant revealed its unique architecture and captured snapshots of its membrane fusion in action.
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