排序方式: 共有25条查询结果,搜索用时 0 毫秒
1.
MV Kondaurova TR Bergeson LC Dilley 《The Journal of the Acoustical Society of America》2012,132(2):1039-1049
Recent studies have demonstrated that mothers exaggerate phonetic properties of infant-directed (ID) speech. However, these studies focused on a single acoustic dimension (frequency), whereas speech sounds are composed of multiple acoustic cues. Moreover, little is known about how mothers adjust phonetic properties of speech to children with hearing loss. This study examined mothers' production of frequency and duration cues to the American English tense/lax vowel contrast in speech to profoundly deaf (N?=?14) and normal-hearing (N?=?14) infants, and to an adult experimenter. First and second formant frequencies and vowel duration of tense (/i/,?/u/) and lax (/I/,?/?/) vowels were measured. Results demonstrated that for both infant groups mothers hyperarticulated the acoustic vowel space and increased vowel duration in ID speech relative to adult-directed speech. Mean F2 values were decreased for the /u/ vowel and increased for the /I/ vowel, and vowel duration was longer for the /i/, /u/, and /I/ vowels in ID speech. However, neither acoustic cue differed in speech to hearing-impaired or normal-hearing infants. These results suggest that both formant frequencies and vowel duration that differentiate American English tense/lx vowel contrasts are modified in ID speech regardless of the hearing status of the addressee. 相似文献
2.
[reaction: see text] The use of the p-toluenesulfonyl (Ts) and tosylvinyl (Tsv) groups as nitrogen masking groups imparted high regioselectivity in Diels-Alder reactions directed toward members of the oroidin-derived marine alkaloid family. The electron-withdrawing Tsv group was utilized as an electronically adjustable nitrogen-protecting group as subsequent hydrogenation provided the more electron-rich tosylethyl (Tse) group. This electronic adjustment strategy avoided a protecting group exchange and provided the required electronics for the key chlorination/ring-contraction sequence. 相似文献
3.
4.
Campbell L.P. Dilley C.E. Gottschalk S.C. Kimura W.D. Quimby D.C. Steinhauer L.C. Babzien M. Ben-Zvi I. Gallardo J.C. Kusche K.P. Jr. Pogorelsky I.V. Skaritka J.R. Van Steenbergen A. Yakimenko V.E. Cline D.B. Ping He Yabo Liu Pantell R.H. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》2000,28(4):1143-1151
The goal of the staged electron laser acceleration (STELLA) experiment is to demonstrate staging of the laser acceleration process whereby an inverse free electron laser (IFEL) will be used to prebunch the electrons, which are then accelerated in an inverse Cerenkov accelerator (ICA). As preparation for this experiment, a new permanent magnet wiggler for the IFEL was constructed and the ICA system was modified. Both systems have been tested on a new beamline specifically built for STELLA. The improved electron beam (e-beam) with its very low emittance (0.8 mm-mrad normalized) enabled focusing the e-beam to an average radius (1σ) of 65 μm, within the ICA interaction region. This small e-beam focus greatly enhanced the ICA process and resulted in electron energy spectra that have demonstrated the best agreement to date in both overall shape and magnitude with the model predictions. The electron energy spectrum using the new wiggler in the IFEL was also measured. These results will be described as well as future improvements to the STELLA experiment 相似文献
5.
Energy spectra for decaying 2D turbulence in a bounded domain 总被引:1,自引:0,他引:1
We use results derived in the framework of the replica approach to study the liquid-glass thermodynamic transition. The main results are derived without using replicas and applied to the study of the Lennard-Jones binary mixture introduced by Kob and Andersen. We find that there is a phase transition due to the entropy crisis. We compute both analytically and numerically the value of the phase transition point T(K) and the specific heat in the low temperature phase. 相似文献
6.
M. B. Maple R. P. Dickey A. Amann E. J. Freeman C. Sirvent M. C. de Andrade N. R. Dilley 《Physica B: Condensed Matter》2000,280(1-4):347-348
The temperature-composition (T–x) phase diagram and NFL characteristics in the electrical resistivity ρ(T), specific heat C(T), and magnetic susceptibility χ(T) at low temperatures for the systems U1−xMxPd2Al3 (M=Y,Th) are described. The T–x phase diagram, the NFL characteristics, and the underlying mechanism for the NFL behavior are distinctly different for M=Y3+ and Th4+, apparently reflecting the difference in valence of the M atom substituents, and suggesting that U is tetravalent in these two systems. 相似文献
7.
Both Class I (intact) and Class II (without the outer plastid membrane) chloroplasts of Spinacea oleracea exhibit a shrinkage of the thylakoid volume under conditions which lead to the well known light-induced light scattering increases. In the present report this shrinkage has been measured on micrographs prepared by the freeze-etch technique. In cloroplasts kept in darkness through the freezing or in those treated with DCMU prior to exposure to red light, the thylakoids are in a slightly swollen condition: in plastids exposed to red light and no inhibitor, the thylakoid membranes are closely appressed, giving the thylakoid a shrunken appearance relative to the control. It is further shown that Class I chloroplasts which are actively fixing CO2 do not give appreciable light scattering changes, but lowering the pH away from the optimum for ATP formation (and CO2 fixation) or adding the uncoupler quinacrine restores the light-induced scattering increases. 相似文献
8.
We report the results of optical studies of new heavy fermion compounds YbFe(4)Sb(12) and CeRu(4)Sb(12). We show that these compounds, as well as several other heavy fermion materials with a nonmagnetic ground state, obey a universal scaling relationship between the quasiparticle effective mass m(*) and the magnitude of the energy gap Delta in the excitation spectrum. This result is in accord with the picture of hybridization of localized f-electron and free carrier states. 相似文献
9.
10.
Nathan D. Lowhorn W. Wong-Ng Z. Q. Lu E. Thomas M. Otani M. Green N. Dilley J. Sharp T. N. Tran 《Applied Physics A: Materials Science & Processing》2009,96(2):511-514
We have successfully developed a Seebeck coefficient Standard Reference Material (SRM™), Bi2Te3, that is crucial for inter-laboratory data comparison and for instrument calibration. Certification measurements were performed
using two different techniques on 10 samples randomly selected from a batch of 390 bars. The certified Seebeck coefficient
values are provided from 10 to 390 K. The availability of this SRM will validate the measurement accuracy, leading to a better
understanding of the structure/property relationships, and the underlying physics of new and improved thermoelectric materials.
An overview of the measurement techniques and data analysis is given. 相似文献