Recently, battery technology has come to require a higher rate capability. The main difficulty in high-rate charge-discharge experiments is kinetic problems due to the slow diffusion of Li-ions in electrodes. Nanosizing is a popular way to achieve a higher surface area and shorter Li-ion diffusion length for fast diffusion. However, while various nanoelectrodes that provide excellent high-rate capability have been synthesized, a size-controlled synthesis and a systematic study of nanocrystalline LiCoO2 have not been carried out because of the difficulty in controlling the size. We have established the size-controlled synthesis of nanocrystalline LiCoO2 through a hydrothermal reaction and, for the first time, clarified the structural and electrochemical properties of this intercalation cathode material. Lattice expansion in nanocrystalline LiCoO2 was found from powder X-ray diffraction measurements and Raman spectroscopy. Electrochemical measurements and theoretical analyses on nanocrystalline LiCoO2 revealed that extreme size reduction below 15 nm was not favorable for most applications. An excellent high-rate capability (65% of the 1 C rate capability at 100 C) was observed in nanocrystalline LiCoO2 with an appropriate particle size of 17 nm.

No abstract

No abstract

Alzheimer's disease (AD), the most common neurodegenerative disorder, results in progressive degeneration of synapses and aberrant sprouting of axon terminals. The mechanisms underlying these seemingly opposing cellular phenomena are unclear. We hypothesized that Fyn kinase may play a role in one or both of these processes because it is increased in AD brains and because it is involved in synaptic plasticity and axonal outgrowth. We investigated the effects of Fyn on AD-related synaptotoxicity and aberrant axonal sprouting by ablating or overexpressing Fyn in human amyloid precursor protein (hAPP) transgenic mice.On the fyn ϩ/ϩ background, hAPP/amyloid ␤ peptide (A␤) decreased hippocampal levels of synaptophysin-immunoreactive presynaptic terminals (SIPTs), consistent with previous findings. On the fyn Ϫ/Ϫ background, hAPP/A␤ did not affect SIPTs. SIPT reductions correlated with hippocampal A␤ levels in hAPP/fyn ϩ/ϩ , but not hAPP/fyn Ϫ/Ϫ , mice suggesting that Fyn provides a critical link between hAPP/A␤ and SIPTs. Furthermore, overexpression of Fyn exacerbated SIPT reductions in hAPP mice. We also found that the susceptibility of mice to hAPP/A␤-induced premature mortality was decreased by Fyn ablation and increased by Fyn overexpression. In contrast, axonal sprouting in the hippocampus of hAPP mice was unaffected. We conclude that Fyn-dependent pathways are critical in AD-related synaptotoxicity and that the pathogenesis of hAPP/A␤-induced neuronal alterations may be mechanistically heterogenous.Key words: Alzheimer's disease; amyloid ␤; Fyn kinase; synaptic deficits; signaling; sprouting; GAP-43; neurodegeneration IntroductionThe amyloid precursor protein (APP) is expressed in many cell types and is particularly abundant in synapses. One of its metabolites, amyloid ␤ peptide (A␤), suppresses synaptic transmission and may participate in the regulation of neuronal activity (Hsia et al., 1999;Kamenetz et al., 2003). Mutations in the human APP (hAPP) gene that lead to increased levels of A␤ cause autosomal dominant familial Alzheimer's disease (FAD) (Selkoe and Schenk, 2003). Of several species of A␤ produced, the 42-residue form (A␤1-42) is particularly susceptible to aggregation and is a primary constituent of neuritic amyloid plaques, pathological hallmarks of the disease (Selkoe and Schenk, 2003). Both FAD and sporadic AD are associated with a progressive degeneration of neurons and synapses (DeKosky and Scheff, 1990;Terry et al., 1999) and an aberrant sprouting of axon terminals (Geddes et al., 1985;Masliah et al., 1991;Arendt, 2001). The precise relationship between hAPP, A␤, plaques, synaptic loss, axonal sprouting, and cognitive decline in AD is unknown.Although amyloid plaques are a diagnostic feature of AD, growing evidence suggests that plaques may not be the primary cause of AD-related synaptic alterations and cognitive decline. In transgenic (TG) mice overexpressing hAPP/A␤ in neurons, synaptic and behavioral deficits are detectable well before plaque formation (Holcomb et al., 1999;Hsia et al., 199...

Recently, a variety of thiolated gold alloy clusters with well-defined compositions have been synthesized, and the effect of doping on their properties and stability has been studied extensively. We examined the occupation site of the Pd dopant within Au 24 Pd 1 (SC 12 H 25 ) 18 by probing complementarily the local environments of Au and Pd elements using 197 Au Mossbauer and Pd K-edge EXAFS spectroscopy, respectively. The experimental results suggest that the doped single Pd atom is preferentially located at the center of Au 24 Pd 1 (SC 12 H 25 ) 18 to form the superatomic Pd@Au 12 core, which supports recent theoretical predictions. These spectroscopic measurements also clarified intracluster electron transfer from the Pd atom to the surrounding Au atoms.

To examine the physiological role of the Fyn tyrosine kinase in neurons, we generated transgenic mice that expressed a fyn cDNA under the control of the calcium͞cal-modulin-dependent protein kinase II␣ promoter. With this promoter, we detected only low expression of Fyn in the neonatal brain. In contrast, there was strong expression of the fyn-transgene in neurons of the adult forebrain. To determine whether the impairment of long-term potentiation (LTP) observed in adult fyn-deficient mice was caused directly by the lack of Fyn in adult hippocampal neurons or indirectly by an impairment in neuronal development, we generated fyn-rescue mice by introducing the wild-type fyn-transgene into mice carrying a targeted deletion in the endogenous fyn gene. In fyn-rescue mice, Schaffer collateral LTP was restored, even though the morphological abnormalities characteristic of fyn-deficient mice were still present. These results suggest that Fyn contributes, at least in part, to the molecular mechanisms of LTP induction.Fyn, one of the Src-related non-receptor tyrosine kinases, is highly expressed in the central nervous system and the immune system. A physiological role for Fyn in brain function was first suggested by the analysis of fyn-deficient mice generated by homologous recombination. These mice exhibited an impaired long-term potentiation (LTP), a long-lasting enhancement of synaptic transmission that is thought to be the cellular basis for learning and memory, as well as a spatial learning impairment (1). Interestingly, in contrast to Fyn, the disruption of other members of the Src family kinases does not cause any obvious neurological phenotypes (2) or any alteration in LTP (1). These results suggest that Fyn signaling may contribute to neuronal plasticity. However, the analysis of the phenotype in fyn-deficient mice was complicated by the presence of a number of other neurological defects, including uncoordinated hippocampal architecture, reduced neural cell adhesion molecule-dependent neurite outgrowth, and decreased susceptibility to kindling (1, 3, 4). In addition, some other lines of fyn-deficient mice expressing a fyn-␤-galactosidease fusion protein showed abnormal suckling behavior, impaired myelination, increased fearfulness, and enhanced seizure susceptibility (5-8). The observed pleiotropic effect of the lack of Fyn suggests that, in the brain, Fyn might be involved in several signal transduction pathways in a variety of cell types and at different developmental stages.To determine whether Fyn is directly involved in the signaling pathway required for LTP induction or if the phenotype observed is solely due to the malformation of the hippocampus, we attempted to rescue Fyn expression in the fyn-deficient mice by expressing fyn cDNA on a fyn-deficient genetic background. For this purpose, we used the calcium͞calmod-ulin-dependent protein kinase II␣ (CaMKII␣) promoter so that the transgene is expressed postnatally only in the forebrain and in neurons and not in glial cells. LTP was normal in the hi...

Mg 2+ intercalation/deintercalation is achieved by using aqueous electrolytes and Prussian blue analog electrodes. Ex situ X-ray diffraction evidenced the solid solution process of Mg 2+ intercalation/deintercalation, while the 57 Fe Mössbauer spectroscopy and Xray absorption near edge structure revealed redox of both Cu and Fe.

Four types of beta-galactoside alpha 2,3-sialyltransferase (ST3Gal I-IV) have been cloned from several animals, but some contradictory observations regarding their substrate specificities and expression have been reported. Therefore, it is necessary to concurrently analyze the substrate specificities of the four enzymes, of which the source should be one animal. Accordingly, the acceptor substrate specificities and gene expression of mST3Gal I-IV were analyzed. Since we had already cloned ST3Gal I and II, as previously reported (Lee, Y.-C. et al., Eur. J. Biochem., 216, 377-385 (1993); J. Biol. Chem., 269, 10028-10033 (1994)), the cDNAs of ST3Gal III and IV were cloned from mouse cDNA libraries. Each of the four enzymes was expressed in COS-7 cells as a recombinant enzyme fused with protein A, and applied on an IgG-Sepharose gel to eliminate endogenous sialyltransferase activity. ST3Gal I and II showed the highest activity toward Gal beta 1, 3 GalNAc (type III), very low activity toward Gal beta 1,3GlcNAc (type I), but none toward Gal beta 1,4GlcNAc (type II). ST3Gal III and IV exhibited high activity toward the type I and II disaccharides, but very low activity toward the type III one. On the other hand, asialo-GM1 (Gg4Cer) was as good a substrate for ST3Gal I and II as the type III disaccharide, though ST3Gal III and IV hardly utilized glycolipids as substrates, as indicated by in vitro experiments. Northern blot analysis revealed that enzymes of the ST3Gal-family are expressed mainly in a tissue-specific manner. The ST3Gal I gene was strongly expressed in spleen and salivary gland, and weakly in brain, liver, heart, kidney, and thymus. The ST3Gal II gene was strongly expressed in brain, and weakly in colon, thymus, salivary gland, and testis, and developmentally expressed in liver, heart, kidney, and spleen. The ST3Gal III and IV genes were expressed in a wide variety of tissues. These differences in tissue specific expression suggest the expression of each ST3Gal influences the distribution of sialyl-glycoconjugates in vivo.