Radiation-induced polymerization at high dose rate. V. Butadiene in bulk

Bulk butadiene was polymerized by a cationic mechanism in a wide dose rate range. The M?_n of the product was about 2300, independent of dose rate. The polymer had 83% residual unsaturation and the remaining double bond was 77% trans and 23% vinyl and had no cis unit. When the polymer yield exceeded 10% gel was formed, but the value of the residual unsaturation in the polymer remained unchanged. This indicated a mechanism that correlated propagation, cyclization, and crosslinking reactions with a cationic intermediate.     

Acoustic variability within and across German, French, and American English vowels: phonetic context effects

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.     

Stable hydrogen isotopic analysis of nanomolar molecular hydrogen by automatic multi-step gas chromatographic separation

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.     

Zwitterionic heterogemini surfactants containing ammonium and carboxylate headgroups 2: aggregation behavior studied by SANS, DLS, and cryo-TEM

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.     

Improvement of texture and palatability of chicken breast: effect of high hydrostatic pressure and sodium hydrogen carbonate

Chicken breast is not preferred in Japan because it is not juicy. In this study, the effect of combined high pressure and sodium hydrogen carbonate (NaHCO₃) treatment on the texture and palatability of chicken breast was investigated. The sample used was broiler chicken breast. Meat samples were soaked in.0–.4 M NaHCO₃ solution and then pressurized at 100–400 MPa. After pressurization, the samples were heated for 30 min at 80°C and cooled down in ice-cold water. High pressure and NaHCO₃ treatment of broiler chicken breast resulted in increased water content, and decreased weight reduction and rupture stress. Moreover, meat exposed to 200 MPa pressurization and.3 M NaHCO₃ treatment was judged tender, juicy and of good taste by sensory evaluation. The combination of high pressure and NaHCO₃ treatment can be effectively used for broiler chicken breast production.     

Determination of the Number of OH Radicals in EB-Irradiated Humid Gases Using Oxidation of CO

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.     

Highly enantioselective michael addition of silyl nitronates to alpha,beta-unsaturated aldehydes catalyzed by designer chiral ammonium bifluorides: efficient access to optically active gamma-nitro aldehydes and their enol silyl ethers

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.     

Distinct advantage of the in situ generation of quaternary ammonium fluorides under phase-transfer conditions toward catalytic asymmetric synthesis

[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.