Acoustic cues to lexical segmentation: a study of resynthesized speech

It has been posited that the role of prosody in lexical segmentation is elevated when the speech signal is degraded or unreliable. Using predictions from Cutler and Norris' [J. Exp. Psychol. Hum. Percept. Perform. 14, 113-121 (1988)] metrical segmentation strategy hypothesis as a framework, this investigation examined how individual suprasegmental and segmental cues to syllabic stress contribute differentially to the recognition of strong and weak syllables for the purpose of lexical segmentation. Syllabic contrastivity was reduced in resynthesized phrases by systematically (i) flattening the fundamental frequency (F0) contours, (ii) equalizing vowel durations, (iii) weakening strong vowels, (iv) combining the two suprasegmental cues, i.e., F0 and duration, and (v) combining the manipulation of all cues. Results indicated that, despite similar decrements in overall intelligibility, F0 flattening and the weakening of strong vowels had a greater impact on lexical segmentation than did equalizing vowel duration. Both combined-cue conditions resulted in greater decrements in intelligibility, but with no additional negative impact on lexical segmentation. The results support the notion of F0 variation and vowel quality as primary conduits for stress-based segmentation and suggest that the effectiveness of stress-based segmentation with degraded speech must be investigated relative to the suprasegmental and segmental impoverishments occasioned by each particular degradation.     

Pb-Pu superlattices: an example of nanostructured actinide materials

Density functional theory applied to Pb-Pu superlattices reveals two competing phases separated by a Mott transition between itinerant and localized 5f electrons. One phase, corresponding to Pu's bulk alpha phase, exhibits paired up Pu planes, thereby broadening the 5f bandwidth. Allowing spin polarization to emulate the energetics of electron correlation leads to another phase with larger volume, narrow 5f bandwidth, and more uniform local crystal structure, similar to bulk fcc Pu.     

Barium‐Mediated Cross‐Dehydrocoupling of Hydrosilanes with Amines: A Theoretical and Experimental Approach

Alkaline‐earth (most prominently barium) complexes of the type [Ae{N(SiMe₃)₂}₂?(THF)_x] and [{N^N}Ae{N(SiMe₃)₂}?(THF)_x] are very active and productive precatalysts (TON=396, TOF up to 3600 h^?1; Ca相似文献   

Photophysics of a Ruthenium 4H‐Imidazole Panchromatic Dye in Interaction with Titanium Dioxide

The photophysics of bis(4,4′‐di‐tert‐butyl‐2,2′‐bipyridine‐κ²N,N′)[2‐(4‐carboxyphenyl)‐4,5‐bis(p‐tolylimino‐κN)imidazolato]ruthenium(II) hexafluorophosphate is investigated, both in solution and attached to a nanocrystalline TiO₂ film. The studied substitution pattern of the 4H‐imidazole ligand is observed to block a photoinduced structural reorganization pathway within the 4H‐imidazole ligand that has been previously investigated. Protonation at the 4H‐imidazole ring decreases the excited‐state lifetime in solution. When the unprotonated dye is anchored to TiO₂, photoinduced electron injection occurs from thermally nonrelaxed triplet metal‐to‐ligand charge transfer (³MLCT) states with a characteristic time constant of 0.5 ps and an injection efficiency of roughly 25 %. Electron injection from the subsequently populated thermalized ³MLCT state of the dye does not take place. The energy of this state seems to be lower than the conduction band edge of TiO₂.     

How Does Peripheral Functionalization of Ruthenium(II)–Terpyridine Complexes Affect Spatial Charge Redistribution after Photoexcitation at the Franck–Condon Point?

Ruthenium polypyridine‐type complexes are extensively used sensitizers to convert solar energy into chemical and/or electrical energy, and they can be tailored through their metal‐to‐ligand charge‐transfer (MLCT) properties. Much work has been directed at harnessing the triplet MLCT state in photoinduced processes, from sophisticated molecular architectures to dye‐sensitized solar cells. In dye‐sensitized solar cells, strong coupling to the semiconductor exploits the high reactivity of the (hot) singlet/triplet MLCT state. In this work, we explore the nature of the ¹MLCT states of remotely substituted Ru^II model complexes by both experimental and theoretical techniques. Two model complexes with electron‐withdrawing (i.e. NO₂) and electron‐donating (i.e. NH₂) groups were synthesized; these complexes contained a phenylene spacer to serve as a spectroscopic handle and to confirm the contribution of the remote substituent to the ¹MLCT transition. [Ru(tpy)₂]²⁺‐based complexes (tpy=2,2′:6′,2′′‐terpyridine) were further desymmetrized by tert‐butyl groups to yield unidirectional ¹MLCTs with large transition dipole moments, which are beneficial for related directional charge‐transfer processes. Detailed comparison of experimental spectra (deconvoluted UV/Vis and resonance Raman spectroscopy data) with theoretical calculations based on density functional theory (including vibronic broadening) revealed different properties of the optically active bright ¹MLCT states already at the Franck–Condon point.     

(−)‐Englerin A is a Potent and Selective Activator of TRPC4 and TRPC5 Calcium Channels

Current therapies for common types of cancer such as renal cell cancer are often ineffective and unspecific, and novel pharmacological targets and approaches are in high demand. Here we show the unexpected possibility for the rapid and selective killing of renal cancer cells through activation of calcium‐permeable nonselective transient receptor potential canonical (TRPC) calcium channels by the sesquiterpene (?)‐englerin A. This compound was found to be a highly efficient, fast‐acting, potent, selective, and direct stimulator of TRPC4 and TRPC5 channels. TRPC4/5 activation through a high‐affinity extracellular (?)‐englerin A binding site may open up novel opportunities for drug discovery aimed at renal cancer.     

A Separation‐Integrated Cascade Reaction to Overcome Thermodynamic Limitations in Rare‐Sugar Synthesis

Enzyme cascades combining epimerization and isomerization steps offer an attractive route for the generic production of rare sugars starting from accessible bulk sugars but suffer from the unfavorable position of the thermodynamic equilibrium, thus reducing the yield and requiring complex work‐up procedures to separate pure product from the reaction mixture. Presented herein is the integration of a multienzyme cascade reaction with continuous chromatography, realized as simulated moving bed chromatography, to overcome the intrinsic yield limitation. Efficient production of D ‐psicose from sucrose in a three‐step cascade reaction using invertase, D ‐xylose isomerase, and D ‐tagatose epimerase, via the intermediates D ‐glucose and D ‐fructose, is described. This set‐up allowed the production of pure psicose (99.9 %) with very high yields (89 %) and high enzyme efficiency (300 g of D ‐psicose per g of enzyme).     

Hydration of guanidinium depends on its local environment

Hydration of gaseous guanidinium (Gdm⁺) with up to 100 water molecules attached was investigated using infrared photodissociation spectroscopy in the hydrogen stretch region between 2900 and 3800 cm^–1. Comparisons to IR spectra of low-energy computed structures indicate that at small cluster size, water interacts strongly with Gdm⁺ with three inner shell water molecules each accepting two hydrogen bonds from adjacent NH₂ groups in Gdm⁺. Comparisons to results for tetramethylammonium (TMA⁺) and Na⁺ enable structural information for larger clusters to be obtained. The similarity in the bonded OH region for Gdm(H₂O)₂₀ ⁺ vs. Gdm(H₂O)₁₀₀ ⁺ and the similarity in the bonded OH regions between Gdm⁺ and TMA⁺ but not Na⁺ for clusters with <50 water molecules indicate that Gdm⁺ does not significantly affect the hydrogen-bonding network of water molecules at large size. These results indicate that the hydration around Gdm⁺ changes for clusters with more than about eight water molecules to one in which inner shell water molecules only accept a single H-bond from Gdm⁺. More effective H-bonding drives this change in inner-shell water molecule binding to other water molecules. These results show that hydration of Gdm⁺ depends on its local environment, and that Gdm⁺ will interact with water even more strongly in an environment where water is partially excluded, such as the surface of a protein. This enhanced hydration in a limited solvation environment may provide new insights into the effectiveness of Gdm⁺ as a protein denaturant.     

Improved Spectral Coverage and Fluorescence Quenching in Donor–acceptor Systems Involving Indolo[3‐2‐b]carbazole and Boron‐dipyrromethene or Diketopyrrolopyrrole

A novel π‐conjugated triad and a polymer incorporating indolo[3,2‐b]‐carbazole (ICZ) and 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY) were synthesized via a Sonogashira coupling. Compared to the parent BODIPY the absorption and fluorescence spectrum were for both compounds broader and redshifted. The redshift of the fluorescence and the decrease of the fluorescence quantum yield and decay time upon increasing solvent polarity were attributed to the formation of a partial charge‐transfer state. Upon excitation in the ICZ absorption band the ICZ fluorescence was quenched in both compounds mainly due to energy transfer to the BODIPY moiety. In a similar ICZ–π–DPP polymer (where DPP is diketopyrrolopyrrole), a smaller redshift of the absorption and fluorescence spectra compared to the parent DPP was observed. A less efficient quenching of the ICZ fluorescence in the ICZ–π–DPP polymer could be related to the unfavorable orientation of the transition dipoles of ICZ and DPP. The rate constant for energy transfer was for all compounds an order of magnitude smaller than predicted by Förster theory. While in a solid film of the triad a further redshift of the absorption maximum of nearly 100 nm was observed, no such shift was observed for the ICZ–π–BODIPY polymer.