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1.
Nathanael Ackerman Cameron Freer Aleksandra Kwiatkowska Rehana Patel 《Annals of Pure and Applied Logic》2017,168(1):19-36
We consider the space of countable structures with fixed underlying set in a given countable language. We show that the number of ergodic probability measures on this space that are -invariant and concentrated on a single isomorphism class must be zero, or one, or continuum. Further, such an isomorphism class admits a unique -invariant probability measure precisely when the structure is highly homogeneous; by a result of Peter J. Cameron, these are the structures that are interdefinable with one of the five reducts of the rational linear order . 相似文献
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Labiche M Orr NA Marqués FM Angélique JC Axelsson L Benoit B Bergmann UC Borge MJ Catford WN Chappell SP Clarke NM Costa G Curtis N D'Arrigo A de Góes Brennand E Dorvaux O Fazio G Freer M Fulton BR Giardina G Grévy S Guillemaud-Mueller D Hanappe F Heusch B Jones KL Jonson B Le Brun C Leenhardt S Lewitowicz M Lopez MJ Markenroth K Mueller AC Nilsson T Ninane A Nyman G de Oliveira F Piqueras I Riisager K Saint Laurent MG Sarazin F Singer SM Sorlin O Stuttgé L 《Physical review letters》2001,86(4):600-603
The two-neutron halo nucleus (14)Be has been investigated in a kinematically complete measurement of the fragments ((12)Be and neutrons) produced in dissociation at 35 MeV/nucleon on C and Pb targets. Two-neutron removal cross sections, neutron angular distributions, and invariant mass spectra were measured, and the contributions from electromagnetic dissociation (EMD) were deduced. Comparison with three-body model calculations suggests that the halo wave function contains a large nu(2s(1/2))(2) admixture. The EMD invariant mass spectrum exhibited enhanced strength near threshold consistent with a nonresonant soft-dipole excitation. 相似文献
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p palan BS 《Physical review letters》1987,58(16):1597-1599
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Appropriately substituted unsymmetrical diaryl carbonates react smoothly with primary amines to give the carbamates derived by nucleophilic displacement of the less electron rich aromatic substituent. Subsequent treatment of the carbamates with primary and secondary amines gives either symmetrical or unsymmetrical ureas in excellent yield and the overall process can be carried out as a “one pot” operation. Acetonitrile is the preferred solvent and addition of DBU facilitates the carbamate → urea transformation. 相似文献
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Molar extinction coefficients of some carbohydrates viz. l-arabinose (C5H10O5), d-glucose (C6H12O6), d-mannose (C6H12O6), d-galactose (C6H12O6), d(-) fructose (C6H12O6) and maltose (C12H24O12) in aqueous solutions have been determined at 81, 356, 511, 662, 1173 and 1332 keV by gamma ray transmission method in a
narrow beam good geometry set-up. These coefficients have been found to depend upon the photon energy following a 4-parameter
polynomial. These extinction coefficients for different sugars having the same molecular formula have same values varying
within experimental uncertainty. Within concentration ranges studied, Beer-Lambert law is obeyed very well. 相似文献
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