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41.
Ildikó Kriston Gábor Pénzes Gábor Szijjártó Pál Szabó Enik? Földes Béla Pukánszky 《Polymer Degradation and Stability》2010,95(9):1883-1893
The processing stabilising performance of various phosphorous antioxidants in polyolefins is affected significantly by their chemical composition. In order to explore the mechanism of stabilisation, the reactions of a hindered aryl phosphite [tris(2,4-di-tert-butylphenyl)phosphite (DTBPP), Hostanox PAR 24] were investigated at temperatures corresponding to polyethylene processing. The thermal and thermo-oxidative stability of the additive was determined by differential scanning calorimetric (DSC) and thermogravimetric methods. DTBPP was heat treated under argon and oxygen at 200 and 240 °C. The stabiliser was reacted at 200 °C with azobisisobutyronitrile (AIBN) in oxygen-free environment (carbon centred radicals) and under oxygen (peroxy radicals), with dicumyl peroxide (DCP) in oxygen atmosphere (oxy radicals), and with cumene hydroperoxide (CHP) under argon. The reaction products were identified by FT-IR, HPLC and HPLC-MS. The results revealed that besides the known reactions of hindered aryl phosphites, thermal decomposition and recombination reactions also take place above the melting point of the antioxidant. DTBPP does not react with molecular oxygen, but its decomposition is accelerated by oxygen and especially by radicals. Accordingly, the heat-stability of phosphorous stabilisers also has to be taken into account in their application, as it is one of the factors which influence the processing stabilisation of polyolefins. 相似文献
42.
F. Vanderbist P. Leleux C. Angulo E. Casarejos M. Couder M. Loiselet G. Ryckewaert P. Descouvemont M. Aliotta T. Davinson Z. Liu P. J. Woods 《The European Physical Journal A - Hadrons and Nuclei》2006,27(2):183-186
The 15O(α,α)15O elastic scattering is investigated using a 15O radioactive beam and a He gas cell limited by Mylar windows. The width of a 19Ne state at an excitation energy of 5.35MeV is measured as Γα = 3.2±1.6keV, in agreement with charge symmetry estimate. 相似文献
43.
A New and Facile Synthesis of Novel Pyrazolothienopyrimidines and Imidazopyrazolothienopyrimidines
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4‐Amino‐3‐methyl‐1‐phenyl‐1H‐thieno[2,3‐c]pyrazole‐5‐carboxamide ( 5 ), which was synthesized by an innovative method, was used as a versatile precursor for synthesizing pyrazolothienopyrimidines and imidazopyrazolothienopyrimidines compounds. Reaction of amino thienopyrazole carboxamide 5 with triethyl orthoformate afforded thienopyrazolopyrimidine 6 . Chlorination of the latter compound, using phosphorus oxychloride afforded the chloro pyrazolothienopyrimidine 7 , which underwent nucleophilic substitution reactions with various primary and secondary amines to give the alkyl (aryl) amino pyrimidine compounds 8a–d . On the other hand, the reaction of chloropyrimidine 7 with thiourea afforded the pyrimidine thione compound 9 , which was alkylated with α‐halogentaed compounds to afford the S‐alkylated derivatives 10a–c . Also, chloroacetylation of the amino carboxamide 5 using chloroacetyl chloride yielded the chloromethyl pyrazolothienopyrimidine 12 , which underwent nucleophilic substitu‐ tion reactions with various primary and secondary amines to afford the alkyl (aryl) aminomethyl compounds 13a–f . The latter Compounds underwent Mannich reaction to give imidazopyrimidothieno‐ pyrazoles 14a–c . The newly synthesized compounds and their derivatives were fully characterized by elemental and spectral analysis. 相似文献
44.
In this account, we provide a brief summary of recent developments in ruthenium‐catalyzed metathesis cascade reactions towards the total synthesis of natural products. We also highlight recent progress from our own laboratory regarding the synthesis of securinega alkaloids and humulanolides, which has resulted in the development of novel ruthenium‐catalyzed metathesis cascade reactions. Inspired and guided by the pioneering and elegant research conducted in this area, we developed a regio‐controlled relay dienyne metathesis cascade reaction and a cyclobutene‐promoted RCM/ROM/RCM cascade reaction for the synthesis of securinega alkaloids and humulanolides, respectively. 相似文献
45.
H. Iwasaki T. Motobayashi H. Akiyoshi Y. Ando N. Fukuda H. Fujiwara Zs. Fülöp K. I. Hahn Y. Higurashi M. Hirai I. Hisanaga N. Iwasa T. Kijima A. Mengoni T. Minemura T. Nakamura M. Notani S. Ozawa H. Sagawa H. Sakurai S. Shimoura S. Takeuchi T. Teranishi Y. Yanagisawa M. Ishihara 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):55-58
Experimental studies on in-beam γ-ray spectroscopy using a 12Be radioactive beam are presented. Inelastic scattering of the neutron-rich 12Be nucleus on 208Pb, 12C, and (CH2)n targets has been studied by measuring de-excitation γ-rays in coincidence with scattered particles. The level schemes and
transition probabilities are determined for low-lying excited states in 12Be. The present paper presents a brief review of the spectroscopic results, which may be associated with the N = 8 shell quenching near the drip line.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
46.
The study of excited 55Mn levels with the 52Cr(α, pγ) reaction was extended to levels up to 3161 keV. With a Ge(Li) detector, DSA measurements in gold-backed targets were made, as well as angular correlations; both of these experiments were done in coincidence with protons detected near 180°. A multiple-detector NaI(Tl) array was also used in the same reaction geometry for better γ-ray detection efficiency. Mean lifetimes of 12 levels from 2727 to 3161 keV are reported. Spins and sometimes parities of the following levels were deduced from the angular-correlation analyses and lifetime results: 1885 keV, ?; 2199 keV, (?); 2311 keV, (); 2366keV, ?; 2727 keV, ; 2823 keV, . Multipole mixing ratios and M1 and E2 transition rates of the radiations from these and from the 1292 keV level are presented. The similarity of the low-lying level structure and of interlevel transitions in 55Mn to those in certain other f3 nuclei is examined. 相似文献
47.
A “Coulomb-modified” dispersion relation is applied to low-energy p-4He forward elastic scattering. To check the validity of the modification, the results are compared with those deduced from n-4He elastic scattering. Completely analogous information is obtained for the two processes. The exchange of three bound nucleons is found to contribute strongly to N-4He forward scattering. The corresponding 4He-3H-p and 4He-3He-n coupling constants are evaluated as Rp = 3.8±0.3 and Rn = 3.0±0.3, respectively. These constants are related to the strength of the asymptotic wave function of nucleons in 4He and thus to the tail of the nucleon distribution. A comparison of Rp with the empirical proton distribution in 4He as deduced from e-4He elastic scattering shows excellent agreement. From Rp and Rn the effective ranges of the singlet 3H-p and 3He-n interactions in the ground state of 4He are determined to be equal, in accordance with charge symmetry, and to have a value of reff = 1.072±0.006 fm. 相似文献
48.
The reactions (α, 3nγ) and (α, α′nγ) on 88Sr, 90Zr and 92Mo were used to populate excited states in 89Zr, 91Mo and 93Ru. The de-excitation of these states was studied by in-beam γ-ray spectroscopy. The short-lived radioactivity of the 92Mo target was measured in order to study the decay of 93Ru. Many new levels were observed, particularly in 91Mo. They are interpreted as due to the coupling of a neutron hole with known excited states in 90Zr, 92Mo and 94Ru. 相似文献
49.
The coupled-channels method for the treatment of the continuum is used to study the negative parity excited states of the 4He nucleus in the Tamm-Damcoff approximation. It is shown that the splittings within the SU(4) supermultiplet are well reproduced in this calculation when the spin-dependent forces responsible for the removal of the degeneracy are taken appropriately into account. The location of the T = 0, 1? resonance and the admixture of spurious c.m. excitation in the intrinsic excitation are discussed. In addition to interpreting the observed spectrum, the available experimental data for the particle channels are well described by the theory. 相似文献
50.
Angular distributions of tritons from the 6Li(n, t)4He reaction were measured at En = 7.25, 6.77, 6.57, 5.24 and 4.71 MeV. Angular distributions of douterons from respectively, the 6Li(n, d)5He two-body breakup reaction were measured at En = 6.77 and 6.57 MeV, and of protons from the 6Li(n, p)6He reaction at En = 6.77, 5.24 and 4.71 MeV. All these reactions in 6Li were analyzed as direct interaction in the formalism of the distorted wave Born approximation. The optical model for the nuclear interaction was found to apply reasonably well to nuclei as light as 4He, 5He, 6He and 6Li. In addition, 6Li as an alpha-deuteron cluster gives the best bound-state wave function to describe the experimental angular distribution of tritons. The excitation functions at forward angles of the 6Li(n, t)4He, 6Li(n, d)5He and 6Li(n, p)6He reactions were measured for incident neutron energies between 4.4 and 7.3 MeV. It is found that the 6Li(n, d)5He two-body breakup reaction has a threshold at about En = 5.3 MeV. Angular distributions at En = 18.3 MeV for tritons and protons from the 9Be(n, t)7Li and 9Be(n, p)9Li, respectively, were also measured. 相似文献