Synthesis of 3,5-Bis(trifluoromethyl)phenyl-Substituted Pyrazole Derivatives as Potent Growth Inhibitors of Drug-Resistant Bacteria

Enterococci and methicillin-resistant S. aureus (MRSA) are among the menacing bacterial pathogens. Novel antibiotics are urgently needed to tackle these antibiotic-resistant bacterial infections. This article reports the design, synthesis, and antimicrobial studies of 30 novel pyrazole derivatives. Most of the synthesized compounds are potent growth inhibitors of planktonic Gram-positive bacteria with minimum inhibitory concertation (MIC) values as low as 0.25 µg/mL. Further studies led to the discovery of several lead compounds, which are bactericidal and potent against MRSA persisters. Compounds 11, 28, and 29 are potent against S. aureus biofilms with minimum biofilm eradication concentration (MBEC) values as low as 1 µg/mL.     

Pulse duration and collision effects in the multiphoton dissociation of HDCO

Measurements of multiphoton dissociation (MPD) of HDCO gas irradiated by intense CO₂ laser pulses varying in shape and having a duration from 150 ns to ～ 1 μs are reported. It is found that for the same laser pulse energy the short pulses dissociated about an order of magnitude more molecules than the long pulses. Taking into consideration the collision-induced MPD of HDCO previously found, it is shown that to a reasonably good approximation, all the present MPD data for the different pulse durations can be represented on a single, smooth and sharply rising curve of yield versus intensity. This finding is in contrast to the flat intensity response at constant pulse energy found recently for collisionless MPD in SF₆.     

Trilinear mode effects on transport coefficients

The effects of tri-linear modes on transport coefficients is illustrated by explicit calculations for the self-diffusion constant. In two dimensions the form of the asymptotic time behavior of the velocity autocorrelation function is changed from t^-1 (bilinear modes) to (t log t)^-1 (trilinear modes). Thus, no finite mode calculation in two dimensions can yield the correct asymptotic form. A heuristic self-consistent calculation including all mode orders yields the form [t log^{$\text{1}\text{2}$} t]^-1. In three dimensions, the form of the asymptotic time behavior is not changed when higher-order modes are included.     

On the slow dynamics of density fluctuations near the colloidal glass transition

Slow dynamics of density fluctuations near the colloidal glass transition is discussed from a new viewpoint by numerically solving a nonlinear stochastic diffusion equation for the density fluctuations recently proposed by one of the present authors (MT). The effects of spatial heterogeneities on the dynamics of density fluctuations are then investigated in an equilibrium system. The spatial heterogeneities are generated by the nonlinear density fluctuations, while in a nonequilibrium system they are described by a nonlinear deterministic equation for the average number density. The dynamics of equilibrium density fluctuations is thus shown to be quite different from that of nonequilibrium ones, leading to a logarithmic decay followed by less distinct α- and β-relaxation processes. Received 9 March 2002 and Received in final form 19 September 2002     

Molecular hydrodynamics of inhomogeneous systems: The origin of slip boundary conditions

Molecular hydrodynamic equations derived by linear response theory for inhomogeneous systems are investigated in two extreme cases: a simple fluid in a gravitational field (an example of a long-range inhomogeneity), and a simple fluid in the presence of a rigid flat wall described by an infinite potential step (an example of a short-range inhomogeneity). In both cases the phenomenological equations result when the molecular equations are smoothed over a length which is large compared to the correlation lenght. For these systems the local equilibrium assumption is shown to be valid. In addition it is shown how the usual slip boundary conditions arise as a consequence of the interaction which causes the short-range inhomogeneity.