Description: This article discusses simultaneous measurement of the average ion-induced electron emission yield and the mean charge for isotachic ions in carbon foils. Knowledge of the incident ion's atomic number (Z₁) dependence of ion-induced electron emission yields can be the basis for a general understanding of ion-atom interaction phenomena and, in particular, for the design of Z₁-sensitive detectors that could be useful, for example, in the separation of isobars in accelerator mass spectrometry. The Z₁ dependence of ion-induced electron emission yields, y, has been investigating using heavy ions C³⁺, O³⁺, F³⁺, Na³⁺, Al³⁺, Si³⁺, P³⁺, S³⁺, Cl³⁺, K³⁺, Ti³⁺, Cr³⁺, Mn⁴⁺, Fe⁴⁺, Co⁴⁺, Ni⁴⁺, Cu⁴⁺, Ga⁴⁺, As⁵⁺, Br⁵⁺, Ru⁷⁺, Ag⁷⁺, Sn⁷⁺, and I⁸⁺ of identical velocity (v = 2v₀, where v₀ is the Bohr velocity) normally incident on 50 μg/cm² sputter-cleaned carbon foils. Measured yields as a function of Z₁ reveal an oscillatory behavior with pronounced maxima and minima. Contrary to previously reported yields that assumed to monotonically increasing empirical mean charge state for the exiting ion, the present work indicates the Z₁ oscillations in the experimentally measured yields, a fact masked in previous work. The strong Z₁ oscillations can only be observed by simultaneous measurement of the yield and the ...

Description: This article is a reply to a comment by Massimo Falcioni and Angelo Vulpiani. In a previous letter, the authors have discussed the linear response theory (LRT) and shown that the breakdown of this theory occurring at intermediate times, observed in an earlier paper [2] as well as in [1], disappears upon an increase of the number of degrees of freedom. In a comment to [1] Falcioni and Vulpiani [3] claim that this breakdown is rather a consequence of the lack of mixing: according to them, regardless of the number of degrees of freedom, mixing is the key ingredient behind the LRT.

Description: This article discusses molecular modeling of vanadium-oxo complexes. Abstract: A force field for vanadium-oxos was developed and tested with a variety of complexes with coordination numbers of 5 or 6 and formal oxidations states of +4 or +5 on the metal. Similarly, a semiempirical quantum mechanical method for transition metals was extended to vanadium. In this research soft and hard ligands were studied, as were ligands coordinated through single, multiple, and dative bonds. Despite the diversity of vanadium coordination chemistry, generally good modeling is achieved in a fraction of the time with less computational resources using molecular mechanics and semiempirical quantum mechanics. The L₄V⁴⁺O and L₅V⁵⁺O groups were emphasized given their prevalence and importance. In general, the predictive ability was superior for the former structural motif. The combination of molecular mechanics and semiempirical quantum calculations provide an effective and efficient tool for analysis of the steric and electronic energy differences between isomers.

Description: This article discusses fractional Brownian motion as a nonstationary process. Abstract: The long-range correlations in DNA sequences are currently interpreted as an example of stationary fractional Brownian motion (FBM). First the authors show that the dynamics of a dichotomous stationary process with long-range correlations such as that used to model DNA sequences should correspond to Lévy statistics and not to FBM. To explain why, in spite of this, the statistical analysis of the data seems to be compatible with FBM, the authors notice that an initial Gaussian condition, generated by a process foreign to the mechanism establishing the long-range correlations and consequently implying a departure from the stationary condition is maintained approximately unchanged for very long times. This is so because due to the nature itself of the long-range correlation process, it takes virtually an infinite time for the system to reach the genuine stationary state. Then the authors discuss a possible generator of initial Gaussian conditions, based on a folding mechanism of the nucleic acid in the cell nucleus. The model adopted is compatible with the known biological and physical constraints, namely, it is shown to be consistent with the information of current biological literature on folding as well ...

Description: This article discusses anomalous diffusion and ballistic peaks. Abstract: The quantum kicked rotor and the classical kicked rotor are both shown to have truncated Lévy distributions in momentum space, when the classical phase space has accelerator modes embedded in a chaotic sea. The survival probability for classical particles at the interface of an accelerator mode and the chaotic sea has an inverse power-law structure, whereas that for quantum particles has a periodically modulated inverse power law, with the period of oscillation being dependent on Planck's constant. These logarithmic oscillations are a renormalization group property that disappears as ħ → 0 in agreement with the correspondence principle.