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The impurity resistivity of Cr between 1.5 and 50°K was determined with a characteristic temperature for the T2 variation θ1=960±40°K. The behaviour of the resistivity minimum both in Cr and Mn alloys with impurity concentration provides evidence that a T3 phonon resistivity is found also in aluminium with anomalous impurity resistivity. 相似文献
84.
We experimentally and numerically study the phenomenon of ghost resonance in coupled nonlinear systems. Two mutually injected semiconductor lasers are externally perturbed in their pump currents by two respective periodic signals of different frequencies f(1) and f(2). For small amplitudes of the external modulations, the two laser intensities display synchronized optical pulses, in the form of dropout events occurring at irregular times. By adjusting the amplitude and frequencies of the driving signals, the system exhibits a ghost resonance in the dropout appearance at a frequency f(r) not present in the distributed inputs. 相似文献
85.
López-Martens R Varjú K Johnsson P Mauritsson J Mairesse Y Salières P Gaarde MB Schafer KJ Persson A Svanberg S Wahlström CG L'huillier A 《Physical review letters》2005,94(3):033001
We report the generation, compression, and delivery on target of ultrashort extreme-ultraviolet light pulses using external amplitude and phase control. Broadband harmonic radiation is first generated by focusing an infrared laser with a carefully chosen intensity into a gas cell containing argon atoms. The emitted light then goes through a hard aperture and a thin aluminum filter that selects a 30-eV bandwidth around a 30-eV photon energy and synchronizes all of the components, thereby enabling the formation of a train of almost Fourier-transform-limited single-cycle 170 attosecond pulses. Our experiment demonstrates a practical method for synthesizing and controlling attosecond waveforms. 相似文献
86.
Adler T Bonjoch J Clayden J Font-Bardía M Pickworth M Solans X Solé D Vallverdú L 《Organic & biomolecular chemistry》2005,3(17):3173-3183
N-Acylated 2-substituted anilines undergo slow Ar-N bond rotation, allowing in some cases isolation of enantiomeric or diastereoisomeric atropisomers and in others the determination of the rate of Ar-N bond rotation by NMR. 2-Iodoanilides bearing a branched N-substituent demonstrate sufficient enantiomeric stability to be resolvable, either by HPLC or by formation of diastereoisomeric lactanilide derivatives. For the first time, the rates of Ar-N rotation in 2-substituted N,N'-diarylureas have been established: they mainly fall in the region of 50-70 kJ mol(-1) with a relatively weak dependence on substituent size. 相似文献
87.
Diego M. Monzón Tanausú Santos Dr. F. Pinacho‐Crisóstomo Prof. Víctor S. Martín Dr. Romen Carrillo 《化学:亚洲杂志》2018,13(3):325-333
Transition metal‐free radical arylation of heteroarenes is achieved at room temperature by simply adding aqueous sodium carbonate to a solution of the corresponding heteroarene and arenediazonium salt, which can even be formed in situ. Such an easy, inexpensive and mild methodology has been optimized and applied to the expeditious modification of interesting molecular cores like naphthylimide or bisthienylcyclopentenes. 相似文献
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Ramírez J Corberán R Sanaú M Peris E Fernandez E 《Chemical communications (Cambridge, England)》2005,(24):3056-3058
Catalytic diboration of internal and terminal alkenes with Ag(I) N-heterocyclic carbene complexes leads to 1,2-bis(boronate) esters as single intermediates, that can be oxidised towards the corresponding diols. 相似文献
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