Transition on the entropic elasticity of DNA induced by intercalating molecules

We use optical tweezers to perform stretching experiments on DNA molecules when interacting with the drugs daunomycin and ethidium bromide, which intercalate the DNA molecule. These experiments are performed in the low-force regime from zero up to 2 pN. Our results show that the persistence length of the DNA-drug complexes increases strongly as the drug concentration increases up to some critical value. Above this critical value, the persistence length decreases abruptly and remains practically constant for larger drug concentrations. The contour length of the molecules increases monotonically and saturates as drugs concentration increases. Measured in- tercalants critical concentrations for the persistence length transition coincide with reported values for the helix-coil transition of DNA-drug complexes, obtained from sedimentation experiments.Comment: This experimental article shows and discuss a transition observed in the persistence length of DNA molecules when studied as a function of some intercalating drug concentrations, like daunomycin and ethidium bromide. It has 15 pages and 4 figures. The article presented here is in preprint forma

Beach and cliff retreat induced by storm groups at Forte Novo,Algarve (Portugal)

Littoral cell dynamics may change through time as a reaction to modifications of the coastal system. Along the Vilamoura-Quarteira coastline, the construction of a groin field limited the sediment supply to the already narrow Forte Novo beach, located downdrift, enhanced wave action on the cliff base and lead to long-term persistent cliff retreat. This research uses a set of surveys from November 2009 to March 2010 to determine short-term soft cliff erosion associated to storm groups at this sediment starved area. Following the initial LiDAR survey, three subsequent surveys were performed using a reflectorless total station for monitoring the cliff face, and RTK-DGPS to monitor the position of the cliff top, the cliff foot and the topography of the adjacent beach. Results indicate an important reduction in beach levels during successive storms (without significant beach recovery in between), allowing waves to further attack the cliff base and contributing to further enhance the structural and permanent cliff retreat. This work demonstrates how a combination of magnitude and frequency of extreme events coupled with development of the coastline, has led to increased cliff-beach recession and to the permanent dislocation of the cliff face

Flavour changing strong interaction effects on top quark physics at the LHC

We perform a model independent analysis of the flavour changing strong interaction vertices relevant to the LHC. In particular, the contribution of dimension six operators to single top production in various production processes is discussed, together with possible hints for identifying signals and setting bounds on physics beyond the standard model.Comment: Authors corrections (references added

On the κ\kappa-Dirac Oscillator revisited

This Letter is based on the $\kappa$-Dirac equation, derived from the $\kappa$-Poincar\'{e}-Hopf algebra. It is shown that the $\kappa$-Dirac equation preserves parity while breaks charge conjugation and time reversal symmetries. Introducing the Dirac oscillator prescription, $\mathbf{p}\to\mathbf{p}-im\omega\beta\mathbf{r}$, in the $\kappa$-Dirac equation, one obtains the $\kappa$-Dirac oscillator. Using a decomposition in terms of spin angular functions, one achieves the deformed radial equations, with the associated deformed energy eigenvalues and eigenfunctions. The deformation parameter breaks the infinite degeneracy of the Dirac oscillator. In the case where $\varepsilon=0$, one recovers the energy eigenvalues and eigenfunctions of the Dirac oscillator.Comment: 5 pages, no figures, accepted for publication in Physics Letters

Faceted anomalous scaling in the epitaxial growth of semiconductor films

We apply the generic dynamical scaling theory (GDST) to the surfaces of CdTe polycrystalline films grown in glass substrates. The analysed data were obtained with a stylus profiler with an estimated resolution lateral resolution of $l_c=0.3 \mu$m. Both real two-point correlation function and power spectrum analyses were done. We found that the GDST applied to the surface power spectra foresees faceted morphology in contrast with the self-affine surface indicated by the local roughness exponent found via the height-height correlation function. This inconsistency is explained in terms of convolution effects resulting from the finite size of the probe tip used to scan the surfaces. High resolution AFM images corroborates the predictions of GDST.Comment: to appear in Europhysics Letter