Biosensing based on two-photon fluorescence measurements through optical fibers

We have performed two-photon fluorescence detection in a new scheme in which femtosecond laser pulses were delivered thorugh an optical fiber for nonlinear excitation and the emitted fluorescence was collected through the same fiber. Single-mode fibers were determined to give higher detection efficiency than multimode fibers, consistent with theoretical considerations. The utility of fiber-optic sensing based on two-photon fluorescence detection was proved by an experiment that measured the uptake of a targeted drug delivery agent into cultured cancer cells.     

On the origin of thermal anomalies in amorphous systems

We examine the possibility that the origin of tunnelling modes in amorphous systems can be traced to certain structural properties following from the observed correlation between amorphous state formation and the occurrence of polymorphism. The physical consequences of this proposition are found to be consistent with many measured properties associated specifically with the amorphous state. The model offers, in particular, a possible explanation for the long standing low temperature specific heat anomalies in b.c.c. ³He.     

Hopping time of a hard disk fluid in a narrow channel

We use Monte Carlo (MC) and molecular dynamics (MD) methods to study the self-diffusion of hard disk fluids, confined within a narrow channel. The channels have a pore radius of Rp, above the passing limit of hard disk diameter (sigma(hd)). We focus on the average time (tau(hop)) needed for a hard disk to hop past a nearest neighbor in the longitudinal direction. This parameter plays a key role in a recent theory of the crossover from single-file diffusion to the bulk limit. For narrow channels near the hopping threshold (Rp=1 in units of sigma(hd)), both MC and MD results for tau(hop) diverge as approximately (Rp-1)(-2). Our results indicate that the scaling law exponent does not appear to be dependent on the differences between the two dynamics. This exponent is consistent with the prediction of an approximate transition state theory.     

Bis(phosphite) Ligands with Distal Regulation: Application in Rhodium‐mediated Asymmetric Hydroformylations

Small amounts of achiral polyether binders are employed to enhance the enantioselectivity of the hydroformylation of an array of diversely substituted substrates (increase of up to 62 % ee for vinyl acetate) mediated by chiral rhodium complexes derived from the α,ω‐bis(phosphite)–polyether ligands 1 . To the best of our knowledge, this study represents an unprecedented successful example of the positive regulation of enantioselectivity in hydroformylations.