Hairy Particles: Polymer Brush-Supported Organocatalysts and Asymmetric Mixed Homopolymer Brushes

This dissertation presents the synthesis and studies of polymer brush-supported organocatalysts and asymmetric mixed homopolymer brushes grafted on particles. The brushes were synthesized from initiator-functionalized particles by surface-initiated “living” radical polymerizations. Polymer brush-supported organocatalysts were designed to combine the advantages of both soluble polymer- (high activity) and crosslinked insoluble polymer-supported catalysts (recyclability). Chapter 1 describes the synthesis of a polymer brush-supported 4-N,N-dialkylaminopyridine (DAAP) catalyst from initiator-functionalized latex particles by surface-initiated nitroxide-mediated radical polymerization (NMRP). The hairy particles efficiently catalyzed the acylation of secondary alcohols and Baylis-Hillman reaction and were recycled six times with no or negligible decrease in the reaction yield. Chapter 2 presents the synthesis of a thermosensitive polymer brush-supported DAAP by surface-initiated atom transfer radical polymerization (ATRP) from silica particles with addition of a free initiator. Both hairy particles and the free copolymer formed from the free initiator were used as catalysts for hydrolysis of nitrophenyl acetate at various temperatures. Below the lower critical solution temperature (LCST), the activity of hairy particles was very close to that of the free copolymer. LCST transitions exerted different effects on the reactions catalyzed by hairy particles and the free copolymer. Chapters 3 and 4 present the studies of the effects of chain length disparity and grafting density on phase morphology of mixed brushes grafted on silica particles. A series of mixed poly(tert-butyl acrylate) (PtBA)/polystyrene (PS) brushes with a fixed PtBA molecular weight and various PS molecular weights were grown from silica particles functionalized with a monochlorosilane-terminated asymmetric difunctional initiator (Y-initiator) by sequential ATRP and NMRP. The total grafting densities of these brushes were 0.6 – 0.7 chains/nm2. The morphology of mixed brushes evolved from isolated PS nanodomains, to short PS cylinders, to a nearly bicontinuous nanostructure, and a two-layered nanostructure with the change of chain length disparity of two homopolymers. To study the grafting density effect, a set of high density asymmetric mixed brushes with total grafting densities of 0.9 – 1.2 chains/nm2 was prepared from triethoxysilane- terminated Y-initiator-functionalized silica particles. The feature sizes of the patterns formed from high density mixed brushes were much smaller than those of lower density mixed brushes

Tracking the Sound of Human Affection: EEG Signals Reveal Online Decoding of Socio-Emotional Expression in Human Speech and Voice

This chapter provides a perspective from the latest EEG evidence in how brain signals enlighten the neurophysiological and neurocognitive mechanisms underlying the recognition of socioemotional expression conveyed in human speech and voice, drawing upon event‐related potentials’ studies (ERPs). Human sound can encode emotional meanings by different vocal parameters in words, real‐ vs. pseudo‐speeches, and vocalizations. Based on the ERP findings, recent development of the three‐stage model in vocal processing has highlighted initial‐ and late‐stage processing of vocal emotional stimuli. These processes, depending on which ERP components they were mapped onto, can be divided into the acoustic analysis, relevance and motivational processing, fine‐grained meaning analysis/integration/access, and higher‐level social inference, as the unfolding of the time scale. ERP studies on vocal socioemotions, such as happiness, anger, fear, sadness, neutral, sincerity, confidence, and sarcasm in the human voice and speech have employed different experimental paradigms such as crosssplicing, crossmodality priming, oddball, stroop, etc. Moreover, task demand and listener characteristics affect the neural responses underlying the decoding processes, revealing the role of attention deployment and interpersonal sensitivity in the neural decoding of vocal emotional stimuli. Cultural orientation affects our ability to decode emotional meaning in the voice. Neurophysiological patterns were compared between normal and abnormal emotional processing in the vocal expressions, especially in schizophrenia and in congenital amusia. Future directions highlight the study on human vocal expression aligning with other nonverbal cues, such as facial and body language, and the need to synchronize listener\u27s brain potentials with other peripheral measures

Prefrontal Cortex: Role in Language Communication during Social Interaction

One important question that remains open for the relationship between the brain and social behavior is whether and how prefrontal mechanisms responsible for social cognitive processes take place in language communication. Conventional studies have highlighted the role of inferior frontal gyrus (IFG) in processing context-independent linguistic information in speech and discourse. However, it is unclear how the medial prefrontal cortex (mPFC), the lateral prefrontal cortex (lPFC), and other structures (such as medial superior frontal gyrus, premotor cortex, anterior cingulate cortex, etc.) are involved when socially relevant language is encountered in real-life scenarios. Emerging neuroimaging and patient studies have suggested the association of prefrontal regions with individual differences and impairments in the comprehension of speech act, nonliteral language, or construction-based pragmatic information. By summarizing and synthesizing the most recent functional magnetic resonance imaging (fMRI) studies, this chapter aims to show how neurocognitive components underlying the social function of prefrontal cortex support pragmatic language processing, such as weighing relevant social signals, resolving ambiguities, and identifying hidden speaker meanings. The conclusion lends impact on an emerging interest in neuropragmatics and points out a promising line of research to address the mediating role of prefrontal cortex in the relation of language and social cognition

Experimental Approaches to Socio‐Linguistics: Usage and Interpretation of Non‐Verbal and Verbal Expressions in Cross‐ Cultural Communication

Social context shapes our behavior in interpersonal communication. In this chapter, I will address how experimental psychology contributes to the study of socio-linguistic processes, focusing on nonverbal and verbal processing in a cross-cultural or cross-linguistic communicative setting. A systematic review of the most up-to-date empirical studies will show: 1) the culturally-universal and culturally-specific encoding of emotion in speech. The acoustic cues that are commonly involved in discriminating basic emotions in vocal expressions across languages and the cross-linguistic variations in such encoding will be demonstrated; 2) the modulation of in-group and out-group status (e.g. inferred from speaker’s dialect, familiarity towards a language) on the encoding and decoding of speaker’s meaning; 3) the impact of cultural orientation and cultural learning on the interpretation of social and affective meaning, focusing on how immigration process shapes one’s language use and comprehension. I will highlight the significance of combining the research paradigms from experimental psychology with cognitive (neuro)science methodologies such as electrophysiological recording and functional magnetic resonance imaging, to address the relevant questions in cross-cultural communicative settings. The chapter is concluded by a future direction to study the socio-cultural bases of language and linguistic underpinnings of cultural behaviour

Trends in Usage-Based and Pragmatic Language Processing and Learning: A Bibliometric Analysis on Psycholinguistics and Second-Language Acquisition Studies

This chapter provides bibliometric analyses of novel trends in the research toward pragmatic aspects of language processing and learning in the studies of psycholinguistics and second-language acquisition. Growing interests in the relevant themes are shown with the analysis of the co-occurrence of keywords in a common literature and the bibliographic coupling between literatures. The emergence of novel experimental methodologies, including the application of neuroimaging and machine learning approaches to the psycholinguistic research, provides new opportunities of looking into the pragmatic aspects of language acquisition and invites new empirical research to validate the theories and extend the boundaries of second-language acquisition research in the real-world setting

Context Modeling for Ranking and Tagging Bursty Features in Text Streams

Bursty features in text streams are very useful in many text mining applications. Most existing studies detect bursty features based purely on term frequency changes without taking into account the semantic contexts of terms, and as a result the detected bursty features may not always be interesting or easy to interpret. In this paper we propose to model the contexts of bursty features using a language modeling approach. We then propose a novel topic diversity-based metric using the context models to find newsworthy bursty features. We also propose to use the context models to automatically assign meaningful tags to bursty features. Using a large corpus of a stream of news articles, we quantitatively show that the proposed context language models for bursty features can effectively help rank bursty features based on their newsworthiness and to assign meaningful tags to annotate bursty features. ? 2010 ACM.EI