CO2/O2 exchange in magnesium-water clusters Mg+(H2O)n

Hydrated singly charged metal ions doped with carbon dioxide, Mg2+(CO2)-(H2O)n, in the gas phase are valuable model systems for the electrochemical activation of CO2. Here, we study these systems by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry combined with ab initio calculations. We show that the exchange reaction of CO2 with O2 proceeds fast with bare Mg+(CO2), with a rate coefficient kabs=1.2 10-10cm3s-1, while hydrated species exhibit a lower rate in the range of kabs = (1.2-2.4) 10-11cm3s-1 for this strongly exothermic reaction. Water makes the exchange reaction more exothermic but, at the same time, considerably slower. The results are rationalized with a need for proper orientation of the reactants in the hydrated system, with formation of a Mg2+(CO4)-(H2O)n intermediate while the activation energy is negligible. According to our nanocalorimetric analysis, the exchange reaction of the hydrated ion is exothermic by -1.7 +/- 0.5eV, in agreement with quantum chemical calculations.(VLID)4795174Version of recor

Calcificação nos núcleos da base na tomografia computadorizada: correlação clínica em 25 pacientes consecutivos Basal ganglia calcification on computed tomography: clinical characteristics in 25 patients

Analisamos os aspectos clínicos de 25 pacientes consecutivos que apresentaram calcificação nos núcleos da base na tomografia computadorizada (TC) de crânio. Esta ocorreu em 0,68% de todos os exames realizados no período. Vinte e três pacientes apresentavam condições clínicas diversas, a saber: cefaléia em 7 casos, acidente vascular cerebral em 5, síndrome extrapiramidal em 2, processo expansivo cerebral em 2, epilepsia, retardo do desenvolvimento neuropsicomotor, demência e trauma de crânio em um caso cada ou outras condições neurológicas em 3. Não havia sintomas neurológicos em 2 casos. Em 15 pacientes (60,0%) havia, além da calcificação dos núcleos da base, outras alterações na TC. Correlação clínica foi observada apenas com as outras alterações da TC e não com a calcificação dos núcleos da base, corroborando a hipótese de que esta possa ser um achado incidental.<br>Twenty-five patients presenting basal ganglia calcification were assessed. This finding comprised 0.68% of all skull CT scan carried out during the period. Two patients were neurologically asymptomatic and 23 presented a variety neurological disorders - headache (7 patients), stroke (5 patients), extrapyramidal syndromes (2 patients), tumor (2 patients), epilepsy (1 patient), mental retardation (1 patient), dementia (1 patient), cranial trauma (1 patient), other neurological conditions (3 patients) - or were asymptomatic from the neurological point of view (2 patients). Findings in the CT scan other than the basal ganglia calcification were observed in 15 (60%) patients. There was a clinical-CT scan correlation in these cases but not in those in which the basal ganglia calcification was an isolated finding. This study highlights the fact that basal ganglia calcification is often a nonspecific finding on CT scan and that it may not be possible to establish a clinical-pathological correlation between them