Magnetic and electronic properties of lithium cobalt oxide substituted by nickel

[Abstract] We measured susceptibility, electron-spin resonance, magnetization and electrical conductivity of LiCo1−yNiyO2 powders synthesized by wet-chemistry method using succinic acid as chelating agent. We found unusual properties in the nickel-rich LiCo0.2Ni0.8O2, which shows several resonance lines as a function of the temperature in the range 3.5–300 K. The signal at low magnetic field is attributed to the magnetic domains in the nanostructured sample. The two other lines correspond to the typical ferromagnetic signal observed in powdered compounds. In the temperature range 120–300 K, the unique ESR line centered at 315 mT is the paramagnetic signal with a gyromagnetic factor g=2.12, which is in good agreement with the presence of a high concentration of Ni3+ (3d7) ions. In the nickel-rich oxide, LiNi0.8Co0.2O2, the magnetic data are qualitatively well-described by the model proposed by Drillon and Panissod for a 3D ferromagnetic order.Spanish and French Foreign Office; HF 1999-0101Spanish and French Foreign Office; PAI Picasso 00717T

Layered LiNi0.5Co0.5O2 cathode materials grown by soft-chemistry via various solution methods

[Abstract] The lithiated nickel–cobalt oxide LiNi0.5Co0.5O2 used as cathode material was grown at low-temperature using different aqueous solution methods. The wet chemistry involved the mixture of metal salts (acetates or nitrates) with various carboxylic acid-based aqueous solutions. Physicochemical and electrochemical properties of LiNi0.5Co0.5O2 products calcined at 400–600°C were extensively investigated. The four methods used involved complexing agents such as either citric, oxalic, aminoacetic (glycine), or succinic acid in aqueous medium which functioned as a fuel, decomposed the metal complexes at low temperature, and yielded the free impurity LiNi0.5Co0.5O2 compounds. Thermal (TG–DTA) analyses and XRD data show that powders grown with a layered structure ( space group) have been obtained at temperatures below 400°C by the acidification reaction of the aqueous solutions. The local structure of synthesized products was characterized by Fourier transform infrared (FTIR) spectroscopy. The electrochemical properties of the synthesized products were evaluated in rechargeable Li cells using a non-aqueous organic electrolyte (1 M LiClO4 in propylene carbonate, PC). The LiNi0.5Co0.5O2 positive electrodes fired at 600°C exhibited good cycling behavior

Mycobacterium tuberculosis ClpX Interacts with FtsZ and Interferes with FtsZ Assembly

FtsZ assembly at the midcell division site in the form of a Z-ring is crucial for initiation of the cell division process in eubacteria. It is largely unknown how this process is regulated in the human pathogen Mycobacterium tuberculosis. Here we show that the expression of clpX was upregulated upon macrophage infection and exposure to cephalexin antibiotic, the conditions where FtsZ-ring assembly is delayed. Independently, we show using pull-down, solid-phase binding, bacterial two-hybrid and mycobacterial protein fragment complementation assays, that M. tuberculosis FtsZ interacts with ClpX, the substrate recognition domain of the ClpXP protease. Incubation of FtsZ with ClpX increased the critical concentration of GTP-dependent polymerization of FtsZ. Immunoblotting revealed that the intracellular ratio of ClpX to FtsZ in wild type M. tuberculosis is approximately 1∶2. Overproduction of ClpX increased cell length and modulated the localization of FtsZ at midcell sites; however, intracellular FtsZ levels were unaffected. A ClpX-CFP fusion protein localized to the cell poles and midcell sites and colocalized with the FtsZ-YFP protein. ClpX also interacted with FtsZ mutant proteins defective for binding to and hydrolyzing GTP and possibly for interactions with other proteins. Taken together, our results suggest that M. tuberculosis ClpX interacts stoichiometrically with FtsZ protomers, independent of its nucleotide-bound state and negatively regulates FtsZ activities, hence cell division

Increased percentage of L-selectin+ and ICAM-1+ peripheral blood CD4+/CD8+ T cells in active Graves' ophthalmopathy.

The purpose of the study was to evaluate the percentage of CD4+/CD8+ peripheral T cells expressing CD62L+ and CD54+ in patients with Graves' disease and to assess if these estimations could be helpful as markers of active ophthalmopathy. The study was carried out in 25 patients with Graves' disease (GD) divided into 3 groups: 1/ 8 patients with active Graves' ophthalmopathy (GO) (CAS 3-6, GO complaints pound 1 year), 2/ 9 patients with hyperthyroid GD without symptoms of ophthalmopathy (GDtox) and 3/ 8 patients with euthyroid GD with no GO symptoms (GDeu). The control group consisted of 15 healthy volunteers age and sex matched to groups 1-3. The expression of lymphocyte adhesion molecules was evaluated by using three-color flow cytometry. In GO group the percentage of CD8+CD54+, CD8+CD62L+, CD4+CD54+ and CD4+CD62L+ T cells was significantly higher as compared to controls (p<0.001, p<0.05, p<0.01, p<0.001 respectively). The percentage of CD8+CD54+ T lymphocytes was also elevated in GO group in comparison to hyperthyroid GD patients (p< 0.05). CD4+CD62L+ and CD8+CD54+ percentages were also increased in GDtox and GDeu as compared to controls. We found a positive correlation between the TSHRab concentration and the percentage of CD8+CD62L+ T cells in all studied groups (r= 0.39, p<0.05) and between the TSHRab level and CAS (r= 0.77, p<0.05). The increased percentage of CD8+CD54+ and CD8+CD62L+ T cells in patients with Graves' ophthalmopathy may be used as a marker of immune inflammation activity

Temperature variation of ultrasonic attenuation and phase velocity in VO2 and V2o3 crystals

We report measurements of the change in the ultrasonic attenuation and phase velocity in the vicinity of the phase transitions of VO2 and V2O3. We show that there exists a variation of the attenuation and of the velocity in the high temperature phase of VO 2 which is compatible with the existence of a soft-mode at the R-point of the Brillouin zone. The forces involved should be long-ranged.Nous étudions les variations de l'atténuation ultrasonore et de la vitesse de phase près de la transition de phase de VO2 et V2O 3. Dans la phase haute température de VO2, nous montrons qu'elles sont compatibles avec l'existence d'un mode mou au point R de la zone de Brillouin. Les forces d'interaction doivent être à longue portée

Non-ergodic aging and hierarchical organization in lithium-potassium tantalate crystals

The dielectric constant of $\rm K_{1-x}Li_xTaO_3$, with x = 0.01 and x = 0.025, and specially its value at very long times, measured as a function of time (aging) at 4 K, depends on the cooling rate; this is a non-ergodic behaviour which manifests the lack of self-similarity of the phase space. The response to temperature jumps, similar to that of spin-glasses, is the signature of hierarchical organization of the phase space. For x = 0 (pure $\rm KTaO_3$), the behaviour is ergodic

Kinetics effects in lithium-potassium tantalate crystals

The study of the dielectric and acoustic constants, performed in a $\rm K_{0.99}Li_{0.01}TaO_3$ crystal between 4 and 30 K, puts in evidence a strong analogy between the kinetics of these two susceptibilities. In particular, the two characteristic times measured for each of them have near values and they are roughly constant in all the temperature range. An explanation in terms of tetragonal domains, with quadrupolar order and dipolar disorder, is suggested

Critical behaviour of dark current and spontaneous polarization in ferroelectric SbSI

Dark current and spontaneous polarization, obtained from measurements of pyroelectric current, have been used to study the ferro-paraelectric transition in SbSI crystals. The critical exponent of the spontaneous polarization is found to have the value predicted from a mean field theory (β = 0.51 ± 0.02).Le courant d'obscurité et la polarisation spontanée, obtenus en mesurant le courant pyroélectrique, ont été utilisés pour faire l'étude de la transition ferro-paraélectrique du SbSI. La valeur obtenue pour l'exposant critique de la polarisation spontanée est en accord avec la théorie du champ moyen (β = 0,51 ± 0,02)

Effect of the electric field on the elastic and dielectric properties of a lithium-potassium tantalate crystal

We have measured in a K$_{1-x}$Li$_{x}$TaO$_3$ crystal with x = 1.7 % the elastic constant with longitudinal acoustic waves of frequency between 30 and 330 MHz and the dielectric constant between 10 Hz and 1 MHz in the temperature range from 4 to 200 K under an electric field applied upon cooling. The main effect of the applied field on the dielectric constant is attributed to space charges. The real part of the elastic constant (the sound velocity) was found to increase when the field was applied perpendicular to the acoustic wave vector and to decrease when it was applied parallel to the wave vector. The effect of the cooling rate was also studied. These results are explained by the occurrence of clusters of oriented dipoles borne by the Li$^+$ ions, favoured by the field