Modern Physics Letters B

Analysis of the frequency of occurrence of short oligonucleotides in typical bacterial genomes reveals that they exhibit the statistical characteristics of a DNA sequence of a much shorter length. This peculiar property suggests a model for genome growth in which a genome evolves by random mutation but primarily grows by random segmental self-copying. Computer-generated genome sequence based on this model indeed has statistical properties similar to those of bacterial genomes.

The free energy and the order parameter profile near the phase transition to the superconducting state in bulk Al samples are calculated within a mean-field-like approximation. The results are compared with those for thin films.

In this article, we investigate an exactly solvable model, describing the behavior of electrons in a cylindrical quantum dot GaAs/Ga_1-xAl_xAs with parabolic confinement potential under the influence of external electrical and magnetic fields, directed along the axes of the cylinder. The wave-function and energy levels of the electron are found. An exact analytical expression for the energy of Stark shift is obtained. It has been shown that only the quadratic Stark effect takes place in the considered system. On the basis of the obtained results, the coefficient of direct interband transition in the system is calculated.

In this study, a contact between YBa₂Cu₃O_7-d thin film and Ba_1-xK_xBiO₃ thin film has been fabricated. The typical I–V characteristics of tunneling are shown in the contact to have different superconducting energy gaps. According to the I–V characteristics, the superconducting energy gaps, 2Δ, are calculated as 1.5 meV and 3 meV for YBa₂Cu₃O_7-d and for Ba_1-xK_xBiO₃, respectively, along the c-axis. The contact boundary between these superconducting thin films shows a boundary Josephson junction with tunneling barrier properties.

We have investigated the sign reversal of Hall effect in high-temperature superconductors in the vortex state as a function of temperature for several samples of Gd_1-xPr_xBa₂Cu₃O_7-δ with 0.2 ≥ x ≥ 0 in a magnetic field of 0–2 T. Multiple sign reversals of Hall resistivity have been observed in under-doped and partially over-doped samples. The Gd_1-xPr_xBa₂Cu₃O_7-δ sample with x = 0.1 shows double sign change in Hall resistivity with variation of magnetic field, and a single sign reversal with variation of temperature. While for the x = 0.15 and x = 0.2 samples, no sign reversal is observed, for the x < 0.1 sample, one sign change of Hall resistivity with temperature over the magnetic field region is observed. The tan(θ_H) also shows a similar double sign reversal of Hall resistivity. This can be related to the particle-hole asymmetry and the complex nature of the Fermi surface.

Based on Einstein, Podolsky and Rosen (EPR) quantum entanglement, we construct a new kind of four-mode entangled states of continuous variables in Fock space and examine its complete property and partly non-orthonormal property. A set-up of one beamsplitter and two polarizers can generate such a four-mode entangled state. The discussion can also be extended to constructing more particles' entangled states.