Field ionization of high-Rydberg fragments produced after inner-shell photoexcitation and photoionization of the methane molecule.

We have studied the production of neutral high-Rydberg (HR) fragments from the CH4 molecule at the C 1s → 3p excitation and at the C 1s ionization threshold. Neutral fragments in HR states were ionized using a pulsed electric field and the resulting ions were mass-analyzed using an ion time-of-flight spectrometer. The atomic fragments C(HR) and H(HR) dominated the spectra, but molecular fragments CH(x)(HR), x = 1-3, and H2(HR) were also observed. The production of HR fragments is attributed to dissociation of CH4(+) and CH4(2+) ions in HR states. Just above the C 1s ionization threshold, such molecular ionic states are created when the C 1s photoelectron is recaptured after single or double Auger decay. Similar HR states may be reached directly following resonant Auger decay at the C 1s → 3p resonance. The energies and geometries of the parent and fragment ions have been calculated in order to gain insight into relevant dissociation pathways.

The C 1s and N 1s near edge x-ray absorption fine structure spectra of five azabenzenes in the gas phase.

Near edge x-ray absorption fine structure spectra have been measured and interpreted by means of density functional theory for five different azabenzenes (pyridine, pyridazine, pyrimidine, pyrazine, and s-triazine) in the gas phase. The experimental and theoretical spectra at the N 1s and C 1s edges show a strong resonance assigned to the transition of the 1s electron in the respective N or C atoms to the lowest unoccupied molecular orbital with pi(*) symmetry. As opposed to the N 1s edge, at the C 1s edge this resonance is split due to the different environments of the core hole atom in the molecule. The shift in atomic core-level energy due to a specific chemical environment is explained with the higher electronegativity of the N atom compared to the C atom. The remaining resonances below the ionization potential (IP) are assigned to sigma or pi [corrected] orbitals with mixed valence/Rydberg [corrected] character. Upon N addition, a reduction of intensity is observed in the Rydberg region at both edges as compared to the intensity in the continuum. Above the IP one or more resonances are seen and ascribed here to transitions to sigma(*) orbitals. Calculating the experimental and theoretical Delta(pi) term values at both edges, we observe that they are almost the same within +/-1 eV as expected for isoelectronic bonded pairs. The term values of the pi(*) and sigma(*) resonances are discussed in terms of the total Z number of the atoms participating in the bond.

Fluorescence emission of excited hydrogen atoms after core excitation of water vapor.

The Balmer emission from atomic hydrogen has been recorded across the resonances at the oxygen K edge of the water molecule using synchrotron radiation excitation. The emission is observed to be strongest at excitations to Rydberg resonances. The observations are interpreted using a qualitative model for the dynamics of the core-to-Rydberg excited molecule. The model links the quantum state of the core-excited water molecule via resonant Auger decay and subsequent dissociation to the state of the fluorescing hydrogen atom.

[Oral rehydration: experience in the management of patients with acute gastroenteritis in the emergency room at the Dr. Antonio Ortiz pediatric hospital]. / Rehidratación oral: experiencia en el manejo de pacientes con gastroenteritis aguda en la sala de emergencia hospital pediátrico Dr. Antonio Ortiz.

Oral rehydration solutions containing 50-90 mEq/L of sodium (Na+) have recently been recommended for the ambulatory management of children with acute diarrhea in the United States. We conducted a randomized study comparing the use of a commercial oral rehydration solution (Rehydralyte), containing 75 mEq/L of Na with the usual method of rehydration with an intravenous solution. Patients treated in the University Pediatric Hospital Emergency Room with acute diarrhea were randomly chosen to receive the oral rehydration solution (Rehydralyte) (Group A), control patients (Group B) were hydrated with the usual intravenous fluids, ie, Ringer's Lactate and then a solution of 56 mEq/L of Na. All patients received orientation about this modality of treatment. Both groups were compared as for weight gain, metabolic parameters, duration of diarrhea, impact on complications associated with use of intravenous solution and cost impact. When both groups were compared there were no differences in measurements of clinical, laboratory data and outcome. Advantages of oral rehydration on cost containment and less human suffering were demonstrated. It can be concluded that in Puerto Rican children oral rehydration solution containing 75 mEq/L Na may be used safely for the treatment of acute diarrhea on ambulatory basis.