Alfonso Guerrero

Selection ofCandida glabrata strains with reduced susceptibility to azoles in four liver transplant patients with invasive candidiasis

The cases of four liver transplant recipients who developed invasive candidiasis (2 cholangitis, 1 perihepatic abscess, 1 candidemia) due to azole-resistantCandida glabrata are reported. Three patients were receiving azolic compounds (2 itraconazole, 1 fluconazole) when the infection was diagnosed. All four patients received fluconazole as intestinal decontamination during the first three weeks post transplantation. The infections occurred two months after transplantation in all patients, and in one patientCandida infection was the direct cause of death. Infection of the biliary tree was the origin of candidiasis in three patients; the fourth patient developed neutropenic-related candidemia. Fluconazole MICs exceeded 16 μg/ml in all cases; itraconazole MICs were 16, 2, 1, and 2 μg/ml, respectively. The potential role ofCandida species other thanalbicans in these patients after administration of azole agents is discussed.

The Effect of the Argon Carrier Gas in the Multiphoton Dissociation-Ionization of Tetracene

The multiphoton dissociation-ionization of tetracene at 355 nm using 6.5 nanosecond laser pulses, with and without argon as a carrier gas (CG), has been studied and compared. Ion fragments were analyzed in a time-of-flight mass spectrometer and separated according to their mass-to-charge ratio (m/z). The results show that the dynamic of photodissociation at ∼1010 W cm−2 intensities is strongly influenced by the CG. The suppression of fragmentation channels primarily those relating to the formation of the CHm+ (m = 2, 4), C2H4+ and C5H4+2 ions. CH5+ and CH6+ were observed which have not been reported before in photodissociation tetracene experiments.

Detection of HCO+, NO+, CNOH+ and CH3+ by multiphoton dissociation of the Nitromethane

Using VUV radiation several ionic fragments were observed from the multiphoton dissociation of the Nitromethane. The detection of the molecular ions was focused on: HCO+, NO+, CNOH+ and CH3+ due to their importance in reactions involving the formation of molecules in the interstellar clouds and the surrounding regions of the stars.

Carbon/hydrogen clusters [CnHx+] formation from laser irradiation of coronene

This article presents the photo induced dehydrogenation of a cooled molecular jet of coronene, exposed to 266 nm laser radiation. Using unfocused laser radiation of 1064 nm, synchronously coupled with the ionization laser pulses, a system recently developed. Molecular beams were produced by laser desorption of coronene. Analysis of the photoproducts made by time-of flight mass spectrometer showed that a wide variety of ionic species were formed; more than 300 different species were observed. The results showed carbon clusters C+n with n up to 24 as well as carbon/hydrogen clusters C+nH+x with masses higher than 300 m/z. The effect on the laser irradiance on the formation of different ions, in the rage from 109 W/cm2 to 1010 W/cm2, is discussed as it is reflected on the evolution from the big ions to the smaller ones.

Photofragmentation of Formic Acid

Dissociation and ionization of formic acid was investigated by multiphotonic absorption regime using laser pulse at 355nm in conjunction with TOF mass spectrometry in reflectron mode (R-TOF). From the different type of detected fragment ions is inferred the formation of some small clusters of formic acid.

Two step laser desorption – laser ionization of PAHs. Experimental Setup

We present an experimental setup for the photoionization of PAHs in a cooled molecular beam using laser radiation of 266 nm. Molecular beams was produced by laser desorption of samples using unfocused laser radiation of 522 nm, which was synchronously coupled with ionization laser pulses. At low energies per pulse, <1 mJ, the molecular ionization of PAHs take place in the soft conditions regimen producing a poor molecular dissociation. The R-ToF spectra are mainly characterized by the presence of the parent molecular ion. When buffer gases as Helium were used it helps to avoid the molecular clustering and contributes to the molecular cooling when the adiabatic expansion takes place.

Multiphoton dissociation of CHnCl4-n compounds at 355 nm

The results of the photodissociation of chlorinated methanes: CH4, CH2Cl2, CHCl3, and CCl4, at 355 nm and intensities up to 1010 Wcm−2, are presented. The absorption of two- to five-photons is responsible for the molecule to reach different dissociative electronic states. From the dissociation products the effect of chlorine isotopes, 35Cl and 37Cl, was observed, mainly in the formation of: Cl+, HCl+, CCl+, and CHCl+, and CCl2+.