A decade with nucleic acid-based microbiological methods in safety control of foods

In the last decade, nucleic acid-based methods gradually started to replace or complement the culture-based methods and immunochemical assays in routine laboratories involved in food control. In particular, real-time polymerase chain reaction (PCR) was technically developed to the stage of good speed, sensitivity and reproducibility, at minimized risk of carry-over contamination. Basic advantages provided by nucleic acid-based methods are higher speed and added information, such as subspecies identification, information on the presence of genes important for virulence or antibiotic resistance. Nucleic acid-based methods are attractive also to detect important foodborne pathogens for which no classical counterparts are available, namely foodborne pathogenic viruses. This review briefly summarizes currently available or developing molecular technologies that may be candidates for involvement in microbiological molecular methods in the next decade. Potential of nonamplification as well as amplification methods is discussed, including fluorescent in situ hybridization, alternative PCR chemistries, alternative amplification technologies, digital PCR and nanotechnologies.

Depinning transition of a two-dimensional vortex lattice in a commensurate periodic potential

We use Monte Carlo simulations of the 2D one component Coulomb gas on a triangular lattice, to study the depinning transition of a 2D vortex lattice in a commensurate periodic potential. A detailed finite size scaling analysis indicates this transition to be first order. No significant changes in behavior were found as vortex density was varied over a wide range.