Time-frequency methods for structural health monitoring.

Detection of early warning signals for the imminent failure of large and complex engineered structures is a daunting challenge with many open research questions. In this paper we report on novel ways to perform Structural Health Monitoring (SHM) of flood protection systems (levees, earthen dikes and concrete dams) using sensor data. We present a robust data-driven anomaly detection method that combines time-frequency feature extraction, using wavelet analysis and phase shift, with one-sided classification techniques to identify the onset of failure anomalies in real-time sensor measurements.

[On mechanism of nonlinear laser cleavage of DNA].

Dependences of nonlinear laser cleavage of DNA on a concentration of the free-radical scavenger, beta-mercaptoethanol, have been measured. The obtained data rule out the free-radical mechanism of the nonlinear laser cleavage and agree with the mechanism based on two-quantum excitation energy transfer from a dye to DNA. A high concentration of beta-mercaptoethanol has been found to cause DNA hyperchromicity.

Site-specific laser modification (cleavage) of oligodeoxynucleotides.

Sequence-specific photomodification of oligodeoxynucleotide pAGAGTATTGACTTA ("a target") has been carried out with the aid of complementary fluorescent probes. Such a probe consisted of oligodeoxynucleotide pAATACTCT and a chromophore group attached to its 5' end. Three different derivatives of ethidium bromide were used as a chromophore.

[Highly effective complementary addressed laser modification (cleavage) of oligodeoxynucleotides].

Complementary addressed nonlinear photomodification of oligodeoxynucleotide dAGAGTATTGACTTA ("target") has been carried out by means of fluorescent derivatives of oligonucleotide dpAATACTCT ("addressed chromophore"). Three different ethidium derivatives were used as a chromophore. The photomodification was induced by nitrogen laser radiation (337 nm, 15 MW/cm2), which led to the target cleavage in the addressation region with the yield of the main fragment (8 bases long) about 10%, formation of specific covalent adduct target-addressed chromophore with the yield 20-70%, "hidden" (not revealed by gel electrophoresis) target damages with 7-27% yield (for different chromophores).

[Nonlinear laser photomodification of nucleic acids induced by intercalating dyes].

Results of a cycle of investigations of two-quantum affinity modification of nucleic acids (NA) are presented. The modification is induced by laser excitation of chromophoric molecules which are in intercalative complexes with NA. The following subjects are considered: theoretical basis of the two-quantum affinity modification: experimental investigation of nonlinear scission of DNA; theory and experiment on the light--induced diffusion of DNA.