Results 1 - 10 of 11976
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[en] By using first-principles calculations, we calculate the vibronic fine structure in photoelectron spectra of C20- clusters. Based on our results, we assign one of the recently observed spectra [H. Prinzbach et al. Nature (London) 407, 60 (2000)] to the fullerene structure and, therefore, confirm the experimental claim that the smallest fullerene is really synthesized
[en] In the chiral limit, the amplitude of the decay π0 → γγ is determined by the anomaly induced on the neutral iso-triplet axial current by the EM field. The amplitude is thus given in terms of the only available quantities in that limit, namely, the fine structure and the pion-decay constants.
[en] One scenario proposed to explain the million degree solar corona is a finely stranded corona where each strand is heated by a rapid pulse. However, such fine structure has neither been resolved through direct imaging observations nor conclusively shown through indirect observations of extended superhot plasma. Recently, it has been shown that the observed difference in the appearance of cool and warm coronal loops (∼1 MK and ∼2-3 MK, respectively)-warm loops appearing 'fuzzier' than cool loops-can be explained by models of loops composed of subarcsecond strands, which are impulsively heated up to ∼10 MK. That work predicts that images of hot coronal loops (∼> 6 MK) should again show fine structure. Here we show that the predicted effect is indeed widely observed in an active region with the Solar Dynamics Observatory, thus supporting a scenario where impulsive heating of fine loop strands plays an important role in powering the active corona.
[en] The paper presents a study of the possibilities of using 20MnB5q the Boron micro–alloyed steel in the assembly of the body components. It is investigated whether the steel in question can be deformed without being globulised but only chilled in flux, followed by a normalization treatment, in order to obtain a finer structure with a globulising tendency. The research has been carried out on samples of 20MnB5q indigenous steel, compared with samples from bars imported from the same French and Finnish origin. Finally there are specified the structural and qualitative differences for this micro–alloyed Boron steel, which in addition to the finishing effect of the structure, have contributed to the increase of the mechanical characteristics. This study examines the behaviour of 20MnB5q grade steel in the manufacturing process of assembly components. The effect of trace Boron in steels, especially the influence of Boron on microstructure and properties of these steels were summarized. (paper)
[en] In analogy to f(R) theory, recently a new modified gravity theory, namely the so-called f(T) theory, has been proposed to drive the current accelerated expansion without invoking dark energy. In the present work, by extending Bisabr's idea, we try to constrain f(T) theories with the varying fine structure 'constant', α≡e2/hc. We find that the constraints on f(T) theories from the observational Δα/α data are very severe. In fact, they make f(T) theories almost indistinguishable from ΛCDM model.