RESUMO
The electronic structure and magnetic moments of free Mn2 (+) and Mn3 (+) are characterized by 2p x-ray absorption and x-ray magnetic circular dichroism spectroscopy in a cryogenic ion trap that is coupled to a synchrotron radiation beamline. Our results directly show that localized magnetic moments of 5 µB are created by 3d(5)((6)S) states at each ionic core, which are coupled ferromagnetically to form molecular high-spin states via indirect exchange that is mediated in both cases by a delocalized valence electron in a singly occupied 4s derived antibonding molecular orbital with an unpaired spin. This leads to total magnetic moments of 11 µB for Mn2 (+) and 16 µB for Mn3 (+), with no contribution of orbital angular momentum.
RESUMO
Magnetic spin and orbital moments of size-selected free iron cluster ions Fe{n}{+} (n=3-20) have been determined via x-ray magnetic circular dichroism spectroscopy. Iron atoms within the clusters exhibit ferromagnetic coupling except for Fe{13}{+}, where the central atom is coupled antiferromagnetically to the atoms in the surrounding shell. Even in very small clusters, the orbital magnetic moment is strongly quenched and reduced to 5%-25% of its atomic value while the spin magnetic moment remains at 60%-90%. This demonstrates that the formation of bonds quenches orbital angular momenta in homonuclear iron clusters already for coordination numbers much smaller than those of the bulk.
RESUMO
Anesthesia for the patient with a perforated globe can be complicated. Cognizance of the anatomy and physiology of the eye, including maintenance of intraocular pressure, is essential for the development of an anesthetic plan. Since the induction phase of anesthesia is the most critical period during which intraocular pressure is affected, understanding the pharmacology of the various anesthetic agents and their effects on the eye is important. To avoid increasing intraocular pressure, a smooth, atraumatic induction is desired. However, methods to achieve this end may place the patient at risk for aspiration. Various techniques that attempt to accomplish this goal are described, including the use of narcotics, lidocaine, nitroglycerin, alpha (alpha 2) agonism, beta (beta) adrenergic and calcium channel blockades, plus the laryngeal mask airway.
