Selective breaking of bonds in water with intense, 2-cycle, infrared laser pulses.

One of the holy grails of contemporary science has been to establish the possibility of preferentially breaking one of several bonds in a molecule. For instance, the two O-H bonds in water are equivalent: given sufficient energy, either one of them is equally likely to break. We report bond-selective molecular fragmentation upon application of intense, 2-cycle pulses of 800 nm laser light: we demonstrate up to three-fold enhancement for preferential bond breaking in isotopically substituted water (HOD).

Influencing supercontinuum generation by phase distorting an ultrashort laser pulse.

We show that the spectral distribution of the supercontinuum (SC) generated in barium fluoride is amenable to alteration simply by controlling the second- and third-order phase distortion of incident femtosecond-duration pulses. The second- and third-order phase distortions are controlled by an acoustic-optic programmable dispersive filter (AOPDF). The spectral extent on the blue side of the SC is influenced by independently varying the phase distortion of an ultrashort laser pulse.

Varying coordination modes of amide ligand in group 12 Hg(II) and Cd(II) complexes: synthesis, crystal structure and nonlinear optical properties.

Reactions of the amide ligand, H2L (H2L = N,N'-bis[2-(2-pyridyl)methyl]pyridine-2,6-dicarboxamide) with CdCl2 and Hg(CH3COO)2, in 1 : 1 ratio, at 298 K yield dimeric [Hg(L)]2 (1) and trimeric [Cd3(H2L)4Cl6] (2), respectively. In 1, the H2L is coordinated to Hg(II) via six N-atoms of central and terminal pyridines as well as of deprotonated amido groups, whereas the carbonyl groups remain free. However, in 2, the H2L is coordinated to Cd(II) through terminal pyridine N atoms and O atoms from carbonyl groups, whereas the nitrogen atoms of the central pyridine, two terminal pyridine and of all amido groups remain free.

A search for the sulphur hexafluoride cation with intense, few cycle laser pulses.

It is well established that upon ionization of sulphur hexafluoride, the SF6(+) ion is never observed in mass spectra. Recent work with ultrashort intense laser pulses has offered indications that when strong optical field are used, the resulting "bond hardening" can induce changes in the potential energy surfaces of molecular cations such that molecular ions that are normally unstable may, indeed, become metastable enough to enable their detection by mass spectrometry. Do intense, ultrashort laser pulses permit formation of SF6(+)? We have utilized intense pulses of 5 fs, 11 fs, and 22 fs to explore this possibility.

Yeasts isolated from nosocomial urinary infections: antifungal susceptibility and biofilm production.

Background: Urinary Candida infections in the hospital environment are frequent and need to be better understood.

Aims: To compare the results of antifungal susceptibility profiles of yeasts isolated from patients with urinary infections obtained by broth microdilution method (BM) and by disk diffusion (DD), and also evaluate the capacity of these yeasts to form biofilms.

Methods: Only yeasts obtained from pure urine cultures with counts higher than 10(5) colony-forming units per milliliter, without bacteria development, of symptomatic patients were included.