Cross-language specialization in phonetic processing: English and Hindi perception of /w/-/v/ speech and nonspeech

This study examined the perceptual specialization for native-language speech sounds, by comparing native Hindi and English speakers in their perception of a graded set of English /w/-/v/ stimuli that varied in similarity to natural speech. The results demonstrated that language experience does not affect general auditory processes for these types of sounds; there were strong cross-language differences for speech stimuli, and none for stimuli that were nonspeech. However, the cross-language differences extended into a gray area of speech-like stimuli that were difficult to classify, suggesting that the specialization occurred in phonetic processing prior to categorization.     

Polymeric coacervate coating for flame retardant paper

Cellulose - Cellulosic paper (from wood fibers) is a highly flammable material that is used in corrugated carboard, packaging, printing, and construction. While there is significant work focused on...     

Imaging cytoplasmic cAMP in mouse brainstem neurons

Background  

cAMP is an ubiquitous second messenger mediating various neuronal functions, often as a consequence of increased intracellular Ca²⁺ levels. While imaging of calcium is commonly used in neuroscience applications, probing for cAMP levels has not yet been performed in living vertebrate neuronal tissue before.     

Observation of polarized positrons from an undulator-based source

An experiment (E166) at the Stanford Linear Accelerator Center has demonstrated a scheme in which a multi-GeV electron beam passed through a helical undulator to generate multi-MeV, circularly polarized photons which were then converted in a thin target to produce positrons (and electrons) with longitudinal polarization above 80% at 6 MeV. The results are in agreement with GEANT4 simulations that include the dominant polarization-dependent interactions of electrons, positrons, and photons in matter.     

Observation of the Askaryan effect: coherent microwave Cherenkov emission from charge asymmetry in high-energy particle cascades

We present the first direct experimental evidence for the charge excess in high-energy particle showers and corresponding radio emission predicted nearly 40 years ago by Askaryan. We directed picosecond pulses of GeV bremsstrahlung photons at the SLAC Final Focus Test Beam into a 3.5 ton silica sand target, producing electromagnetic showers several meters long. A series of antennas spanning 0.3 to 6 GHz detected strong, subnanosecond radio-frequency pulses produced by the showers. Measurements of the polarization, coherence, timing, field strength vs shower depth, and field strength vs frequency are completely consistent with predictions. These measurements thus provide strong support for experiments designed to detect high-energy cosmic rays such as neutrinos via coherent radio emission from their cascades.     

Plasticity in vowel perception and production: a study of accent change in young adults

This study investigated changes in vowel production and perception among university students from the north of England, as individuals adapt their accent from regional to educated norms. Subjects were tested in their production and perception at regular intervals over a period of 2 years: before beginning university, 3 months later, and at the end of their first and second years at university. At each testing session, subjects were recorded reading a set of experimental words and a short passage. Subjects also completed two perceptual tasks; they chose best exemplar locations for vowels embedded in either northern or southern English accented carrier sentences and identified words in noise spoken with either a northern or southern English accent. The results demonstrated that subjects at a late stage in their language development, early adulthood, changed their spoken accent after attending university. There were no reliable changes in perception over time, but there was evidence for a between-subjects link between production and perception; subjects chose similar vowels to the ones they produced, and subjects who had a more southern English accent were better at identifying southern English speech in noise.     

Stable isotopic studies of earthworm feeding ecology in tropical ecosystems of Puerto Rico

Feeding strategies of earthworms and their influence on soil processes are often inferred from morphological, behavioral and physiological traits. We used (13)C and (15)N natural abundance in earthworms, soils and plants to explore patterns of resource utilization by different species of earthworms in three tropical ecosystems in Puerto Rico. In a high altitude dwarf forest, native earthworms Trigaster longissimus and Estherella sp. showed less (15)N enrichment ((15)N = 3-6 per thousand) than exotic Pontoscolex corethrurus ((15)N =7-9 per thousand) indicating different food sources or stronger isotopic discrimination by the latter. Conversely, in a lower altitude tabonuco forest, Estherella sp. and P. corethrurus overlapped completely in (15)N enrichment ((15)N = 6-9 per thousand), suggesting the potential for interspecific competition for N resources. A tabonuco forest converted to pasture contained only P. corethrurus which were less enriched in (15)N than those in the forest sites, but more highly enriched in (13)C suggesting assimilation of C from the predominant C(4) grass. These results support the utility of stable isotopes to delineate resource partitioning and potential competitive interactions among earthworm species. Copyright 1999 John Wiley & Sons, Ltd.     

Second-language experience and speech-in-noise recognition: effects of talker-listener accent similarity

Previous work has shown that the intelligibility of speech in noise is degraded if the speaker and listener differ in accent, in particular when there is a disparity between native (L1) and nonnative (L2) accents. This study investigated how this talker-listener interaction is modulated by L2 experience and accent similarity. L1 Southern British English, L1 French listeners with varying L2 English experience, and French-English bilinguals were tested on the recognition of English sentences mixed in speech-shaped noise that was spoken with a range of accents (French, Korean, Northern Irish, and Southern British English). The results demonstrated clear interactions of accent and experience, with the least experienced French speakers being most accurate with French-accented English, but more experienced listeners being most accurate with L1 Southern British English accents. An acoustic similarity metric was applied to the speech productions of the talkers and the listeners, and significant correlations were obtained between accent similarity and sentence intelligibility for pairs of individuals. Overall, the results suggest that L2 experience affects talker-listener accent interactions, altering both the intelligibility of different accents and the selectivity of accent processing.