Modern Physics Letters B

The Polymerase Chain Reaction (PCR) allows for highly sensitive and specific amplification of DNA. It is the backbone of many genetic experiments and tests. Recently, three labs independently uncovered a novel and simple way to perform a PCR reaction. Instead of repetitive heating and cooling, a temperature gradient across the reaction vessel drives thermal convection. By convection, the reaction liquid circulates between hot and cold regions of the chamber. The convection triggers DNA amplification as the DNA melts into two single strands in the hot region and replicates into twice the amount in the cold region. The amplification progresses exponentially as the convection moves on. We review the characteristics of the different approaches and show the benefits and prospects of the method.

A detailed semiempirical quantum-chemical study is reported on homogeneous adenosine-thymidine and guanosine-cytidine base pair steps, both pure ones and their complexes with oxygen molecules. The results of this study help gain detailed insight into physico-chemical mechanisms of electrical conduction control in DNA molecules when doping them with molecular oxygen or related molecules.

We report the results of annealing effects on structural and superconducting properties (T_c and J_c) of various MgB₂/Fe wires that are produced by different conditions. Good quality superconducting MgB₂/Fe wires are fabricated by the powder-in-tube (PIT) technique at ambient pressure. XRD data confirms that they are hexagonalMgB₂ structure. All the annealed samples show higher T_c values in the range of 34.6–38.4 K with J_c higher than the as-rolled wire. The annealed samples show significant change in the J_c values as well as in micro-structural features due to variable sintering temperature. On annealing at 1050°C for 10 min, we obtain the best quality sample with a J_c of 37.2 kA/cm² at 33.1 K and self-field with a maximum T_c of 38.4 K. Among the samples annealed at 1050°C for 5–20 min, the 20 min sample shows lower J_c. Longer annealing time (at 1050°C) reduced J_c, indicating a possible interfacial reaction between the Fe sheath and the MgB₂ core.

EPR and FT-IR spectroscopy have been used to investigate the B₂O₃–Bi₂O₃ glass matrix containing CuO in order to obtain more information about the local structure of these glasses. The EPR absorption spectra revealed the presence in the glass structure of the Cu²⁺ ions in axially distorted octahedral environments. No superexchange interaction of Cu²⁺ was detected. In the samples with x≥5 mol%, mixed valence states of copper ions were revealed. The FT-IR measurements indicate the presence in the glass structure of the distorted [BiO₆] polyhedra, tri- and tetra-borate units (BO₃, BO₄) and its dependence by the copper content.

The recently suggested modified microscopic theory of liquids has been used successfully to explain the collective dynamics of liquid Al near its melting point. Considering the frequency-dependent self-diffusion coefficient occurring in the intermediate self-correlation function, which is inextricably linked with the collective dynamics of the system, the observed variation in dynamical structure factor of Al can be quantitatively reproduced for wave vector range 0.42 Å^-1 to 1.38 Å^-1 taking into account single relaxation time.

The transport properties across contacts between quantum tubes and metals are studied. The curvature effects on the transmission are also considered. We find that the transmission probability of an electron transporting from the tube into the metal through the contact can be close to 100%. The curvature has a larger effect on the transmission for smaller radii and the effects decrease as the radii increase.

Electron spectra of DNA model compounds, adenosine-thymidine and guanosine-cytidine nucleoside base pairs, as well as the relevant homogeneous stacked base pair steps in A-DNA and B-DNA conformations, were investigated using ZINDO semiempirical quantum-chemical method. This work confirms that, in DNA with intact Watson–Crick hydrogen bonding and base stacking, the highest occupied molecular orbitals (HOMO) are residing on purine base residues, whereas the lowest unoccupied molecular orbitals (LUMO) — on pyrimidine base residues. In general, the present results are satisfactorily comparable with the available experimental data. The role of charge transfer excitations in the polymer DNA 260 nm spectral band is discussed.

A method of shared secret key distribution applicable to optical coherent multiplexing systems is proposed. It provides ways to detect the extent of eavesdropping. Detecting test factors and system design rules are suggested, and performance evaluation is performed in terms of mutual information between legitimate users and an eavesdropper. This scheme devises a new way of attaining secure optical communications without entirely relying on computational complexity.

A series of In:Mn:Fe:LiNbO₃ crystals were prepared with fixed concentrations of Fe₂O₃, MnCO₃ and various concentrations of In₂O₃. Their ultraviolet-visible (UV-Vis) absorption spectra were measured in order to investigate their defect structure. The optical damage resistance of In:Mn:Fe:LiNbO₃ crystals was characterized by the transmitted beam pattern distortion method. It increases remarkably when the concentration of In₂O₃ is over its threshold concentration. The optical damage resistance of In(3.0 mol%):Mn:Fe:LiNbO₃ crystal is two orders of magnitude higher that of the Mn:Fe:LiNbO₃ crystal. The dependence of the defects on the optical damage resistance of the In:Mn:Fe:LiNbO₃ crystals was discussed.