Leprosy and tuberculosis concomitant infection: a poorly understood, age-old relationship

Historically, archaeological evidence, post-mortem findings and retro- spective analysis of leprosy institutions’ data demonstrates a high observed incidence of concomitant infection with leprosy and tuberculosis (TB). However, reports of concomitant infection in the modern literature remain scarce, with estimates of annual new case detection rates of concomitant infection at approximately 0·02 cases per 100,000 population. Whilst the mechanism for this apparent decline in concomitant infections remains unclear, further research on this topic has remained relatively neglected. Modelling of the interaction of the two organisms has suggested that the apparent decline in observations of concomitant infection may be due to the protective effects of cross immunity, whilst more recently others have questioned whether it is a more harmful relationship, predisposing towards increased host mortality. We review recent evidence, comparing it to previously held understanding on the epidemiological relationship and our own experience of concomitant infection. From this discussion, we highlight several under-investigated areas, which may lead to improvements in the future delivery of leprosy management and services, as well as enhance understanding in other fields of infection management. These include, a) highlighting the need for greater understanding of host immunogenetics involved in concomitant infection, b) whether prolonged courses of high dose steroids pre-dispose to TB infection? and, c) whether there is a risk of rifampicin resistance developing in leprosy patients treated in the face of undiagnosed TB and other infections? Longitudinal work is still required to characterise these temporal relationships further and add to the current paucity of literature on this subject matter

Transformations of Ruddlesden-Popper Oxides to New Layered Perovskite Oxides by Metathesis Reactions

We report transformations of the Ruddlesden-Popper (R-P) oxide, K2La2Ti3O10, to layered perovskite oxides, (Bi2O2)La2Ti3O10, MLa2Ti3O10 (M = Pb, Ba, Sr), and (VO)La2Ti3O10, by a novel metathesis reaction with BiOCl-, MCI2, and VOSO4. 3H(2)O, respectively. The formation of (VO)La2Ti3O10, which occurs in aqueous medium around 100 degrees C, suggests that the reaction is most likely topotactic, where the structural integrity of the perovskite sheet is preserved. We believe that the method described here provides a new general route for the synthesis/assembly of layered perovskite materials containing MX/M2X2 sheets, as indeed shown by the independent report of (CuX)LaNb2O7 synthesis by a similar reaction

ALaMnBO<SUB>6</SUB> (A=Ca, Sr, Ba; B=Fe, Ru) double perovskites

We report the synthesis and investigation of electrical and magnetic properties of double perovskites of the formula ALaMnBO6 for A = Ca, Sr, Ba and B = Fe, Ru. Powder X-ray diffraction (XRD) shows formation of cubic/pseudocubic perovskite structure for all the phases, with no obvious long-range ordering of B-site cations. Electron diffraction, however, reveals an ordering of Mn and Ru in ALaMnRuO6, showing a doubling of the primitive cubic perovskite cell. While the B = Fe phases are paramagnetic insulators, the B = Ru phases are ferrimagnetic semiconductors. It is likely that in the B = Ru phases, a valence equilibrium exists between MnIII/RuIV and MnII/RuV states that is biased toward the latter

2D-3D transformation of layered perovskites through metathesis: synthesis of new quadruple perovskites A<SUB>2</SUB>La<SUB>2</SUB>CuTi<SUB>3</SUB>O<SUB>12</SUB> (A= Sr, Ca)

We describe the synthesis of two new quadruple perovskites, Sr2La2CuTi3O12 (I) and Ca2La2CuTi3O12 (II), by solid-state metathesis reaction between K2La2Ti3O10 and A2CuO2Cl2 (A = Sr, Ca). I is formed at 920&#176;C/12 h, and II, at 750 &#176;C/24 h. Both the oxides crystallize in a tetragonal (P4/mmm) quadruple perovskite structure (a = 3.9098(2) and c = 15.794(1) &#197; for I; a = 3.8729(5) and c = 15.689(2) &#197; for II). We have determined the structures of I and II by Rietveld refinement of powder XRD data. The structure consists of perovskite-like octahedral CuO4/2O2/2 sheets alternating with triple octahedral Ti3O18/2 sheets along the c-direction. The refinement shows La/A disorder but no Cu/Ti disorder in the structure. The new cuprates show low magnetization (0.0065 &#956;B for I and 0.0033 &#956;B for II) suggesting that the Cu(II) spins are in an antiferromagnetically ordered state. Both I and II transform at high temperatures to 3D perovskites where La/Sr and Cu/Ti are disordered, suggesting that I and II are metastable phases having been formed in the low-temperature metathesis reaction. Interestingly, the reaction between K2La2Ti3O10 and Ca2CuO2Cl2 follows a different route at 650&#176;C, K2La2Ti3O10 + Ca2CuO2Cl2 &#8594; CaLa2Ti3O10 + CaCuO2 + 2KCl, revealing multiple reaction pathways for metathesis reactions

Ionic dispersion of Pt and Pd on CeO<SUB>2</SUB> by combustion method: effect of metal-ceria interaction on catalytic activities for NO reduction and CO and hydrocarbon oxidation

Ceria-supported Pt and Pd catalysts have been synthesized by the combustion method. The catalysts are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Pt and Pd metals are ionically dispersed on the CeO2 surface of crystallite sizes in the range of 15-20 nm. In 1% Pt/CeO2 Pt is found to be in the +2 and +4 oxidation states whereas Pd is in the +2 state in 1% Pd/CeO2. Catalytic activities for NO reduction by CO, NH3, CH4, and C3H8 and CO, CH4, and C3H8 oxidation by O2 have been investigated over all these catalysts using the temperature-programmed reaction technique. The results are compared with Pt and Pd metals dispersed on &#945;-Al2O3 support prepared by the combustion technique. Both oxidation and reduction reactions occur at much lower temperatures over M/CeO2 compared to those over M/Al2O3 (M=Pt, Pd). The rate and turnover frequency of NO+CO and CO+O2 reactions over M/CeO2 are higher than those over M/Al2O3. The observed enhanced catalytic activity of M/CeO2 has been attributed to the ionic dispersion of Pt and Pd on CeO2 leading to a strong metal-ceria interaction in the form of solid solution, Ce1-xMxO2-(4-n)x/2, having linkages of the type -O2--Ce4+-O2--Mn+-O2-- (n=2, 4) on the CeO2 surface

Transforming n=1 members of the Ruddlesden-Popper phases to a n=3 member through metathesis: synthesis of a new layered perovskite, Ca<SUB>2</SUB>La<SUB>2</SUB>CuTi<SUB>2</SUB>O<SUB>10</SUB>

We report the formation of a new n=3 Ruddlesden-Popper (R-P) layered perovskite oxide, Ca2La2CuTi2O10 (I), in the metathesis reaction between NaLaTiO4 and Ca2CuO2Cl2 (n=1 R-P phases) at 700&#176;C in air. Rietveld refinement of powder XRD data shows that I is isostructural with Sr4Ti3O10 (space group I4/mmm; a=3.8837(5), c=27.727(6) &#197;), consisting of triple perovskite CuTi2O10 sheets wherein Cu and Ti are ordered at the central and terminal octahedral sites, respectively. Magnetization data provide support for the presence of strong antiferromagnetically coupled CuO2 sheets in the structure. I is metastable decomposing at higher temperatures (~950&#176;C) to a mixture of perovskite-like CaLa2CuTi2O9 and CaO. Interestingly, the reaction between NaLaTiO4 and Sr2CuO2Cl2 follows a different metathesis route, 2NaLaTiO4+Sr2CuO2Cl2&#8594;La2CuO4+2SrTiO3+2NaCl, revealing multiplicity of reaction pathways for solid-state metathesis reactions

ALaMnBO6ALaMnBO_6 (A = Ca, Sr, Ba; B = Fe, Ru)double perovskites

We report the synthesis and investigation of electrical and magnetic properties of double perovskites of the formula $ALaMnBO_6$ for A = Ca, Sr, Ba and B = Fe, Ru. Powder X-ray diffraction (XRD) shows formation of cubic/pseudocubic perovskite structure for all the phases, with no obvious long-range ordering of B-site cations. Electron diffraction, however, reveals an ordering of Mn and Ru in $ALaMnRuO_6$, showing a doubling of the primitive cubic perovskite cell. While the B = Fe phases are paramagnetic insulators, the B = Ru phases are ferrimagnetic semiconductors. It is likely that in the B = Ru phases, a valence equilibrium exists between $Mn^{III}/Ru^{IV}$ and $Mn^{II}/Ru^V$ states that is biased toward the latter

ALaMnBO6_6 (A=5 Ca, Sr, Ba; B =Fe, Ru) double perovskites

We report the synthesis and investigation of electrical and magnetic properties of double perovskites of the formula ALaMnBO$_6$for A= Ca, Sr, Ba and B = Fe, Ru. Powder X-ray diffraction (XRD) shows formation of cubic/pseudocubic perovskite structure for all the phases, with no obvious long-range ordering of B-site cations. Electron diffraction, however, reveals an ordering of Mn and Ru in ALaMnRuO$_6$, showing a doubling of the primitive cubic perovskite cell. While the B =Fe phases are paramagnetic insulators, the B = Ru phases are ferrimagnetic semiconductors. It is likely that in the B = Ru phases, a valence equilibrium exists between$Mn^{III}$ /$Ru^{IV}$ and $Mn^{II}$, /$Ru^{V}$ states that is biased toward the latter