No abstract

By applying the particle-number projection to the finite-temperature BCS theory, the S-shaped heat capacity, which has recently been claimed to be a fingerprint of the superfluid-to-normal phase transition in nuclei, is reexamined. It is found that the particle-number (or number-parity) projection gives S-shapes in the heat capacity of nuclei which look qualitatively similar to the observed ones. These S-shapes are accounted for as effects of the particle-number conservation on the quasiparticle excitations, and occur even when we keep the superfluidity at all temperatures by assuming a constant gap in the BCS theory. The present study illustrates significance of the conservation laws in studying phase transitions of finite systems.

No abstract

The efficiency of gold nanoparticle (AuNP) dimerization mediated by hybridization between two probe DNA molecules and a complementary target DNA molecule was maximized by examining several possible hybridization combinations. The uniformity of the size of the AuNPs, the use of surface modification appropriate for high hybridization efficiency, together with efficient blocking of nonspecific binding, all contributed to achieving a 1 pM detection limit following conventional gel electrophoresis separation of the DNA-modified AuNP multimers. This practical homogeneous DNA hybridization assay methodology will provide a rapid, cost-effective, and field-portable tool for clinical diagnosis.

Homogeneous DNA assays using gold nanoparticles (AuNPs) require the reduction of nonspecific binding between AuNPs to improve sensitivity in detecting the target molecule. In this study, we employed alkanethiol self-assembled monolayers (SAMs) for modifying the AuNP surface to attain both good dispersability and high hybridization efficiency. The alkanethiol SAMs enhance the repulsive interaction between AuNPs, reducing nonspecific binding and promoting the extension of surface-immobilized ssDNA into the solvent, thus enhancing the hybridization process. Introduction of oligoethylene glycol into the alkanethiol prevented nonspecific binding caused by the entanglement of alkane chains. Finally, the conditions were optimized by controlling the surface charge density through the introduction of a COOH group at the alkanethiol terminus, resulting in the complete blocking of nonspecific binding and the maintenance of high hybridization efficiency.