Electrical Energy Storage and Intercalation Chemistry

The electrochemical reaction of layered titanium disulfide with lithium giving the intercalation compound lithium titanium disulfide is the basis of a new battery system. This reaction occurs very rapidly and in a highly reversible manner at ambient temperatures as a result of structural retention. Titanium disulfide is one of a new generation of solid cathode materials.

High-performance LiNi0.5Mn1.5O4 spinel controlled by Mn3+ concentration and site disorder

The complex correlation between Mn(3+) ions and the disordered phase in the lattice structure of high voltage spinel, and its effect on the charge transport properties, are revealed through a combination of experimental study and computer simulations. Superior cycling stability is achieved in LiNi(0.45)Cr(0.05)Mn(1.5)O(4) with carefully controlled Mn(3+) concentration. At 250th cycle, capacity retention is 99.6% along with excellent rate capabilities.

New iron(III) phosphate phases: crystal structure and electrochemical and magnetic properties

Two new iron(III) phosphates, FePO(4), have been synthesized from the dehydration of hydrothermally prepared monoclinic and orthorhombic hydrated phosphates FePO(4).2H(2)O. The structures of both hydrates were redetermined from single crystal data. On dehydration, a topotactic reaction takes place with only those bonds associated with the water molecules being broken, so that both FePO(4) phases have essentially the same Fe-P backbone frameworks as the corresponding hydrates. They are, respectively, monoclinic FePO(4), space group P2(1)/n, a= 5.480(1) A, b = 7.480(1) A, c= 8.054(1) A, beta = 95.71(1) degrees, and Z = 4; and orthorhombic FePO(4), space group Pbca, a = 9.171(1) A, 9.456(1) A, c = 8.675(1) A, and Z = 8. Both of these phases are thermally unstable relative to the trigonal quartz-like FePO(4). The electrochemical studies find that the orthorhombic iron phosphate is more active than the monoclinic phase, while both are more active than trigonal FePO(4). Both phases approach Curie-Weiss behavior at room temperature, with the monoclinic phase exhibiting stronger antiferromagnetic interactions due to Fe-O-Fe interactions. The electrochemical and magnetic data are consistent with the structures of these two compounds. The properties of these new iron phosphate structures are compared with other iron phosphate phases.

Left ventricular hypertrophy with exercise and ACE gene insertion/deletion polymorphism: a randomized controlled trial with losartan

BACKGROUND

Local cardiac renin-angiotensin systems may regulate left ventricular (LV) hypertrophic responses. The absence (deletion [D]) of a 287-bp marker in the ACE gene is associated with greater myocardial ACE levels and exercise-related LV growth than is its presence (insertion [I]), an effect potentially mediated through either increased activity of the cellular growth factor angiotensin II on the angiotensin type 1 (AT(1)) receptor or increased degradation of growth-inhibiting kinins. We sought to confirm ACE genotype-associated exertional LV growth and to clarify the role of the AT(1) receptor in this association.

METHODS AND RESULTS

One hundred forty-one British Army recruits homozygous for the ACE gene (79 DD and 62 II) were randomized to receive losartan (25 mg/d, a subhypotensive dose inhibiting tissue AT(1) receptors) or placebo throughout a 10-week physical training program. LV mass, determined by cardiac magnetic resonance, increased with training (8.4 g, P:<0.0001 overall; 12.1 versus 4.8 g for DD versus II genotype in the placebo limb, P:=0.022). LV growth was similar in the losartan arm: 11.0 versus 3.7 g for DD versus II genotypes (P:=0.034). When indexed to lean body mass, LV growth in the II subjects was abolished, whereas it remained in the DD subjects (-0.022 versus 0.131 g/kg, respectively; P:=0.0009).

CONCLUSIONS

ACE genotype dependence of exercise-induced LV hypertrophy is confirmed. Additionally, LV growth in DD (unlike II) subjects is in excess of the increase in lean body mass. These effects are not influenced by AT(1) receptor antagonism with the use of losartan (25 mg/d). The 2.4-fold greater LV growth in DD men may be due to the effects of angiotensin II on other receptors (eg, angiotensin type 4) or lower degradation of growth-inhibitory kinins.

Oxygen Loss in Layered Oxide Cathodes for Li-Ion Batteries: Mechanisms, Effects, and Mitigation

Layered lithium transition metal oxides derived from LiMO₂ (M = Co, Ni, Mn, etc.) have been widely adopted as the cathodes of Li-ion batteries for portable electronics, electric vehicles, and energy storage. Oxygen loss in the layered oxides is one of the major factors leading to cycling-induced structural degradation and its associated fade in electrochemical performance. Herein, we review recent progress in understanding the phenomena of oxygen loss and the resulting structural degradation in layered oxide cathodes. We first present the major driving forces leading to the oxygen loss and then describe the associated structural degradation resulting from the oxygen loss. We follow this analysis with a discussion of the kinetic pathways that enable oxygen loss, and then we address the resulting electrochemical fade. Finally, we review the possible approaches toward mitigating oxygen loss and the associated electrochemical fade as well as detail novel analytical methods for probing the oxygen loss.

Composition-structure relationships in the Li-ion battery electrode material LiNi(0.5)Mn(1.5)O(4)

A study of the correlations between the stoichiometry, secondary phases and transition metal ordering of LiNi(0.5)Mn(1.5)O(4) was undertaken by characterizing samples synthesized at different temperatures. Insight into the composition of the samples was obtained by electron microscopy, neutron diffraction and X-ray absorption spectroscopy. In turn, analysis of cationic ordering was performed by combining neutron diffraction with Li MAS NMR spectroscopy. Under the conditions chosen for the synthesis, all samples systematically showed an excess of Mn, which was compensated by the formation of a secondary rock salt phase and not via the creation of oxygen vacancies. Local deviations from the ideal 3:1 Mn:Ni ordering were found, even for samples that show the superlattice ordering by diffraction, with different disordered schemes also being possible. The magnetic behavior of the samples was correlated with the deviations from this ideal ordering arrangement. The in-depth crystal-chemical knowledge generated was employed to evaluate the influence of these parameters on the electrochemical behavior of the materials.

The influence of substrate on the functional response of an avian granivore and its implications for farmland bird conservation

Few studies to date have considered the effect of substrate on the functional response of an organism feeding on prey of varying visibility. Intake rates of lone captive canaries, Serinus canarius L., were measured at varying seed densities on patches of either earth or short grass (<1 cm). Experiment 1, using pale seeds, found intake rates were significantly higher and search times significantly lower on earth than on grass. Two measures of crypticity (contrast in light reflectance as measured using a spectrophotometer and an experiment with humans) found pale seeds to be more visible on earth. The results from experiment 1 could be explained by this difference in crypsis. Experiment 2 used identical seeds to those in experiment 1 except they were dyed to match their backgrounds. The two measures of crypticity both found that black seeds were less visible on earth than green seeds were on grass. However, intake rates were still significantly higher on earth than grass. Seed colour preference, vegetation impeding movement, and differences in vigilance rates or seed accessibility could not explain this result. We discuss three other potentially explanatory mechanisms, the most likely of which was the greater surface area needed for scanning created by the structure of grass. Crucially, regardless of the mechanism(s) involved, many vegetated substrates share similar properties with grass (structural complexity and shiny surfaces which reflect light) and so the outcome of our findings are likely to extend to many natural situations. Conservationists wishing to encourage granivorous birds should consider enhancing food accessibility by providing uniform substrates, such as bare earth, for them to forage on. In addition, behaviour-based models should incorporate the effects of habitat into their equations of the functional response.