52 research outputs found
Excitation and relaxation in atom-cluster collisions
Electronic and vibrational degrees of freedom in atom-cluster collisions are
treated simultaneously and self-consistently by combining time-dependent
density functional theory with classical molecular dynamics. The gradual change
of the excitation mechanisms (electronic and vibrational) as well as the
related relaxation phenomena (phase transitions and fragmentation) are studied
in a common framework as a function of the impact energy (eV...MeV). Cluster
"transparency" characterized by practically undisturbed atom-cluster
penetration is predicted to be an important reaction mechanism within a
particular window of impact energies.Comment: RevTeX (4 pages, 4 figures included with epsf
Jejunal Diverticular Perforation due to Enterolith
Jejunal diverticulosis is a rare entity with variable clinical and anatomical presentations. Although there is no consensus on the management of asymptomatic jejunal diverticular disease, some complications are potentially life-threatening and require early surgical treatment. Small bowel perforation secondary to jejunal diverticulitis by enteroliths is rare. The aim of this study was to report a case of small intestinal perforation caused by a large jejunal enterolith. An 86-year-old woman was admitted with signs of diffuse peritonitis. After initial fluid recovery the patient underwent emergency laparotomy. The surgery showed that she had small bowel diverticular disease, mainly localized in the proximal jejunum. The peritonitis was due to intestinal perforation caused by an enterolith 12 cm in length, localized inside one of these diverticula. The intestinal segment containing the perforated diverticulum with the enterolith was removed and an end-to-end anastomosis was done to reconstruct the intestinal transit. The patient recovered well and was discharged from hospital on the 5th postoperative day. There were no signs of abdominal pain 1 year after the surgical procedure. Although jejunal diverticular disease with its complications, such as formation of enteroliths, is difficult to suspect in patients with peritonitis, it should be considered as a possible source of abdominal infection in the elderly patient when more common diagnoses have been excluded
Structures and reactions of hydrated biomolecular cluster ions
Photo-induced reactions and metastable decompositions of
cluster ions containing glycine, tryptophan, tryptophanylglicine and
[Fe(III)-protoporphyrin]+ (hemin ions solvated with water
molecules are studied with electrospray ionization (ESI). The ESI ion source
is improved to produce hydrated biomolecular cluster ions. Metastable
decompositions of the hydrated clusters following primary mass selection are
measured to determine the incremental solvent binding energies for the
clusters by using evaporative ensemble model. From these experimental
findings, stability of the cluster ions is discussed in terms of
delocalization of ionic charges. We also measure the photodissociation
yields of mass-selected water clusters containing hemin+ ions at 355
and 532Â nm. The mass spectra of photofragments show the -cleavage of
carboxymethyl groups in addition to the evaporation of solvent molecules
Photo-induced reactions of hemin
Photo-induced reaction of [Fe(III)-protoporphyrin]+ (hemin+) ions solvated with
dimethylsulfoxide (DMSO) is investigated by using a tandem mass spectrometer with electrospray
ionization. We measure the photodissociation yields of mass-selected hemin+(DMSO)n clusters for n = 0–3 in the energy region of 15 800–28 200 cm-1. The mass spectra of the fragment ions show the
β-cleavage of carboxymethyl groups in addition to the evaporation of solvent molecules. Yield of the
β-cleavage reaction is found to depend strongly on the excitation energy and the number of solvent
molecules. We also examine the metastable decomposition of the clusters following primary mass
selection and determine the incremental solvent binding energies and internal energies for the clusters
using evaporative ensemble model. From these results, we investigate the reaction mechanism of
β-cleavage of hemin+ ion
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