RESUMO
Agglomerated ZnMn2O4 nanoparticles with average particle sizes of 90-130 nm are synthesized by a facile chemical co-precipitation method. It is found that the consumption of precipitant ammonia has an important impact on the morphology and lithium storage property of the prepared ZnMn2O4 nanomaterials. With increasing ammonia consumption (molar ratios of Zn2+ to the precipitant ammonia of 1:10, 1:15, 1:20 and 1:25, respectively), the particle size of the prepared ZnMn2O4 nanomaterials becomes smaller, the porous morphology formed by the primary nanoparticles agglomeration becomes more obvious, and the lithium storage performance is improved. When Zn2+/ammonia mole ratio is 1:25, the prepared ZnMn2O4 material presents a reversible capacity of 780 mAh g-1 after 200 cycles at a current density of 0.5 A g-1. At a very high current density of 5 A g-1, the sample still retains a reversible capacity of 250 mAh g-1. This superior lithium storage performance of the sample is associated with its porous structure, which benefits the penetration of the electrolyte and enhances the electrochemical reaction activity of the active materials in the electrode. These results suggest that agglomerated ZnMn2O4 nanoparticles prepared by chemical coprecipitation method have potential as anode electroactive materials for next-generation lithium-ion batteries.
RESUMO
OBJECTIVE: To establish a clinical staging system for patients with severe acute respiratory syndrome (SARS) based on clinical feature, laboratory tests as well as dynamic changes of chest X-ray images. METHOD: Dynamic changes of chest X-ray images and laboratory tests in 45 SARS patients managed from March to May, 2003 were analyzed. RESULTS: (1) Chest X-ray image: among 45 cases, 23 were common type: the time to appearance of unilateral patched shadow of the lung were 2 to 5 (2.9 +/- 1.0) days. The time to appearance of bilateral patched shadow of the lungs were 2 to 12 (6.9 +/- 2.5) days. The time to appearance of ground glass or consolidation in the lung were 6 to 19 (11.0 +/- 2.0) days. The time to the beginning of absorption of X-ray changes were 10 to 21 (15.0 +/- 4.1) days. The time for chest X-ray image to be absorbed completely were 18 to 46 (25.9 +/- 7.2) days. Twenty-two patients were severe type, in which the time to the appearance of ground glass of the lung were (9.0 +/- 3.2) days, with no significant difference when compared with common type (P < 0.05). However, the time to the beginning of absorption and complete absorption were (19.0 +/- 4.6) days (P = 0.009) and (36.0 +/- 8.1) days (P = 0.001), respectively. Noticeably, the time to pan-consolidation of the lung were less than 7 days in 7 fatal cases. (2) Laboratory tests: decrease in the number of lymphocytes and T lymphocyte subset were seen in the early stage. While the account recovered in 10 to 14 days of disease course in the 38 patients who survived, there was no recovery in 7 patients who died. CONCLUSIONS: SARS can be divided into five stages: incubation period 2 to 10 days, prodromal period 1 to 3 days, progressive period 4 to 7 days, advanced period 8 to 15 days were, convalescent period 16 to 24 days. The appearance of pan-consolidation in the lung in less than 7 days and/or unable to recover the number of lymphocytes and T lymphocyte subset will be associated with poor prognosis.
