Origin of valence and core excitations in LiFePO(4) and FePO(4).

Electronic structures of LiFePO(4) and FePO(4) have been investigated using valence and core electron energy loss spectroscopy (EELS) supported by ab initio calculations. Valence electron energy loss spectra of FePO(4) are characterized by interband transitions found between 0 and 20 eV, which are not observed in LiFePO(4). Spectra are fully analysed using band structure calculations and calculated dielectric functions. In particular, we show that interband transitions observed in FePO(4) spectra originate from the states at the top of the valence band, which have mainly oxygen p character. From core-loss EELS, it is observed that the O-K edge in FePO(4) has a pre-edge peak below the threshold of the main O-K edge. This pre-edge peak is not observed in the O-K spectra of LiFePO(4). The position of the pre-edge peak is determined by a charge transfer process, which shifts the position of the iron 3d bands with respect to the conduction band. The intensity of the pre-edge peak is also determined by the changes in the hybridization of iron 3d and oxygen states as a result of extraction of lithium ions from the LiFePO(4) lattice. We show that the extraction of lithium ions from LiFePO(4) results in large changes in the electronic structure, such that FePO(4) can be considered to be a charge transfer insulator while LiFePO(4) is a typical Mott-Hubbard insulator.

T-helper type 2-dependent early recruitment of antigen non-specific CD4+ T cells in experimental asthma.

BACKGROUND: Following antigen challenge, adoptively transferred antigen-specific CD4(+) T cells induce allergic airway inflammation, comprised primarily of an increase in lymphocytes and eosinophils. OBJECTIVE: Our goal was to better understand the contribution of the GATA-3 transcription factor to the ability of adoptively transferred T cells to induce airway inflammation in the Brown Norway rat model of adoptively transferred asthma. METHODS: We transduced antigen-stimulated CD4+ T cells with recombinant retroviruses encoding enhanced green fluorescent protein (EGFP) only or EGFP and the GATA-3 transcription factor. Each population of transduced cells was adoptively transferred to naïve recipients that were then challenged with antigen. Airway inflammatory responses were then quantified. RESULTS: Our data indicate that T cells transduced with retroviruses encoding GATA-3 expressed high levels of GATA-3 protein as well as T-helper type 2 cytokines. Following adoptive transfer and airway antigen challenge, these gene-modified T cells induced robust inflammatory responses in the lungs and draining lymph nodes. Increased numbers of total inflammatory cells and eosinophils were recovered in the bronchoalveolar lavage fluid (BALF). In addition, the number of antigen non-specific CD4+ T cells recovered in the BALF as well as the lung and draining lymph nodes was enhanced in recipients of GATA-3 overexpressing T cells following antigen challenge. Nevertheless, the transduced CD4+ T cells comprised only a small percentage of the population of CD4+ T cells infiltrating the lung and were not detectable at all in the draining lymph nodes. CONCLUSION: These data provide evidence that GATA-3 plays a significant role in the ability of antigen-specific T cells to amplify allergic inflammatory responses in vivo by promoting the recruitment of endogenous antigen non-specific T cells to the lung.

Effect of improved stoves on prevalence of acute respiration infection and conjunctivitis among children and women in a rural community in Kenya.

OBJECTIVES: To estimate the effect of improved stoves on the prevalence of ARI and conjunctivitis among children aged below five years and women aged between 15 and 60 years. METHOD: A field trial or intervention study design, in which cluster and random sampling were used to recruit households with improved stoves. Nearest households with traditional three-stone stoves were recruited as controls. Prevalence of ARI and conjunctivitis among the study subjects was estimated by clinical evaluation and physical observation, and by history (including clinical and socioeconomic information), and compared between the two study groups. RESULTS: The prevalence of ARI among children aged below five years and among women aged between 15 and 60 years were significantly higher in households with the traditional three-stone stoves than in those with the improved stove chi 2 = 31.45 rho = 0.00000, relative risk = 2.6, C.I. 1.86,3.63, and chi 2 = 30.13, rho = 0.00000, Relative Risk = 2.8, C.I. 1.93, 4.06, respectively). Similarly the prevalence of conjunctivitis among children aged below five years and among women aged between 15 and 60 years were significantly higher in households with traditional three-stone stoves than in those with the improved stoves (c2 = 24.18, p = 0.00000, Relative Risk = 3.3, C.I. 2.05,5.32, and chi 2 = 7.6, rho = 0.0057, Relative Risk = 3, C.I. 1.38, 6.54, respectively). CONCLUSION: Prevalence of ARI and conjunctivitis among children aged below five years and also among women aged between 15 and 60 years in households with the traditional three-stone stoves was significantly higher than that in households with improved stoves.

Quality control in the laboratory diagnosis of tuberculosis.

The study was conducted in 4 hospital laboratories to assess the value of smear re-examination, duplicate smear and culture in quality control in the diagnosis of pulmonary tuberculosis. In each hospital 1 to 3 sputum specimens were collected from each suspect and examined by the Ziehl-Neelsen method. Smears along with corresponding specimens were sent to the reference laboratory for re-examination and examination of fresh duplicate smears and culture. A total of 994 specimens plus 23 known negative and 23 known positive controls were analysed. For each assessment method, both over-diagnosis and underdiagnosis were indicated with under-diagnosis being a more common problem in the four hospital laboratories. The limitations of these assessment methods are presented.

Sero-epidemiology of Toxoplasma gondii infection in young children in Nairobi, Kenya.

The exposure of 127 pre-school and young schoolchildren to Toxoplasma gondii was investigated by a serological survey of its antibody by means of the passive haemagglutination technique. The significant rise of prevalence of the antibody from 35% in pre-school to 60% in the early school age group suggests that poor sanitary habits and conditions and water shortage in primary schools may cause parasitic infection through contact between children which has not been previously suspected but should be investigated. The strange difference of prevalence of the antibody in the two sexes in the pre-school age children cannot be explained by any social aspects of life. It is therefore suggested the initial exposure of the two sexes to the protozoan is the same but that it acts selectively as a killer disease in the pre-school males either as a primary infection or, more probably, secondary to other lethal paediatric killer diseases. Further studies of the latter aspects in the tropics are needed.