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Strange W Weber A Levy ES Shafiro V Hisagi M Nishi K 《The Journal of the Acoustical Society of America》2007,122(2):1111-1129
Cross-language perception studies report influences of speech style and consonantal context on perceived similarity and discrimination of non-native vowels by inexperienced and experienced listeners. Detailed acoustic comparisons of distributions of vowels produced by native speakers of North German (NG), Parisian French (PF) and New York English (AE) in citation (di)syllables and in sentences (surrounded by labial and alveolar stops) are reported here. Results of within- and cross-language discriminant analyses reveal striking dissimilarities across languages in the spectral/temporal variation of coarticulated vowels. As expected, vocalic duration was most important in differentiating NG vowels; it did not contribute to PF vowel classification. Spectrally, NG long vowels showed little coarticulatory change, but back/low short vowels were fronted/raised in alveolar context. PF vowels showed greater coarticulatory effects overall; back and front rounded vowels were fronted, low and mid-low vowels were raised in both sentence contexts. AE mid to high back vowels were extremely fronted in alveolar contexts, with little change in mid-low and low long vowels. Cross-language discriminant analyses revealed varying patterns of spectral (dis)similarity across speech styles and consonantal contexts that could, in part, account for AE listeners' perception of German and French front rounded vowels, and "similar" mid-high to mid-low vowels. 相似文献
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Komatsu DD Tsunogai U Kamimura K Konno U Ishimura T Nakagawa F 《Rapid communications in mass spectrometry : RCM》2011,25(21):3351-3359
We have developed a new automated analytical system that employs a continuous flow isotope ratio mass spectrometer to determine the stable hydrogen isotopic composition (δD) of nanomolar quantities of molecular hydrogen (H2) in an air sample. This method improves previous methods to attain simpler and lower‐cost analyses, especially by avoiding the use of expensive or special devices, such as a Toepler pump, a cryogenic refrigerator, and a special evacuation system to keep the temperature of a coolant under reduced pressure. Instead, the system allows H2 purification from the air matrix via automatic multi‐step gas chromatographic separation using the coolants of both liquid nitrogen (77 K) and liquid nitrogen + ethanol (158 K) under 1 atm pressure. The analytical precision of the δD determination using the developed method was better than 4‰ for >5 nmol injections (250 mL STP for 500 ppbv air sample) and better than 15‰ for 1 nmol injections, regardless of the δD value, within 1 h for one sample analysis. Using the developed system, the δD values of H2 can be quantified for atmospheric samples as well as samples of representative sources and sinks including those containing small quantities of H2, such as H2 in soil pores or aqueous environments, for which there is currently little δD data available. As an example of such trace H2 analyses, we report here the isotope fractionations during H2 uptake by soils in a static chamber. The δD values of H2 in these H2‐depleted environments can be useful in constraining the budgets of atmospheric H2 by applying an isotope mass balance model. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Nyuta K Yoshimura T Tsuchiya K Sakai H Abe M Iwase H 《Journal of colloid and interface science》2012,388(1):80-85
Metallo-meso-5,10,15,20-tetrakis-(4-sulfonatophenyl)porphyrins (metallo-TPPSs), such as ZnTPPS, have been widely used as photosensitizers. However, their vulnerability to photodegradation significantly limits their applications. In this contribution, we demonstrate a method to enhance the photostability of metallo-TPPSs while retaining photoactivity via encapsulation inside cores of complex micelles. Poly(ethylene glycol)-b-poly(4-vinylpyridine) (PEG-b-P4VP) and metallo-TPPSs can form complex micelles in acidic solution through electrostatic interactions and then undergo axial coordination with the pyridine moieties of PEG-b-P4VP when the pH is adjusted to 7.4. In this way, metallo-TPPSs are entrapped in the hydrophobic, compact micellar cores, which effectively prevents photodegradation of the metallo-TPPSs that would otherwise occur in aqueous solution. In addition, the photodebromination of 2,3-dibromo-3-phenylpropionic acid (DPP) sensitized with ZnTPPS has been used as a model reaction to study the photosensitive activity of ZnTPPS entrapped in complex micelles. The entrapped ZnTPPSs exhibit pronounced activity and have much higher efficiency and faster photosensitive reaction rates than free ZnTPPS. 相似文献
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Teruyuki Hakoda Akihiko Shimada Kanae Matsumoto Koichi Hirota 《Plasma Chemistry and Plasma Processing》2009,29(1):69-78
Electron beam (EB) technology has an advantage for treating dilute environmental pollutants in gases due to high-density population
of active species such as radicals and atoms. In general, OH radicals play an important role of initiating the decomposition
and removal of such pollutants. It is quite important to understand the behavior of OH radical production for the development
of efficient decomposition/removal processes and the comparison with other purification methods. The number of OH radicals
produced in humid N2 at doses of 2.0–10.0 kGy with dose rates of 0.17–2.55 kGy/s under 1-MeV EB irradiation was indirectly determined using an
index of oxidation of CO to CO2, which has been used in atmospheric chemistry. An experiment under conditions where all OH radicals produced react with CO
demonstrated that the concentration of CO2 increased linearly with doses of 0–10 kGy, and the G(OH) was estimated as 4.90. 相似文献
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Highly enantioselective Michael addition of silyl nitronates to alpha,beta-unsaturated aldehydes has been accomplished by the utilization of designer N-spiro C2-symmetric chiral quaternary ammonium bifluoride 1 as an efficient catalyst, providing direct access to both optically active gamma-nitro aldehydes, a very useful precursor to various complex organic molecules including aminocarbonyls, and their enol silyl ethers, a Mukaiyama donor of potential synthetic utility for further selective transformations. For instance, the reaction of trimethylsilyl nitronate 2 (R1 = Me) with trans-cinnamaldehyde (R2 = Ph, R3 = H) in toluene in the presence of (R,R)-1 (2 mol %) proceeded smoothly at -78 degrees C to give the desired enol silyl ether 3 (R1 = Me, R2 = Ph, R3 = H) in 90% isolated yield (anti/syn = 83:17) with 97% ee (anti isomer), and simple treatment of 3 thus obtained with 1 N HCl in THF at 0 degrees C afforded the corresponding gamma-nitro aldehyde 4 quantitatively without loss of diastereo- and enantioselectivity. 相似文献
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[structure in text] Quaternary ammonium fluorides were found to be efficiently generated in situ from the corresponding ammonium hydrogensulfates by treatment with commercially available potassium fluoride dihydrate (KF.2H(2)O) in THF and directly used as a fluoride source for the generation of carbon nucleophiles from organosilicon compounds. This method can be successfully applied to the preparation of structurally well-defined, C(2)-symmetric chiral quaternary ammonium fluorides of type 1 (X = F), thereby allowing catalytic enantioselective Mukaiyama-type aldol reactions under mild conditions. 相似文献
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