Carbon nanotubes prepared in situ in a cellular ceramic by the gelcasting-foam method

The synthesis of carbon nanotubes from an oxide solid solution foam is reported for the first time. A foam of Mg0.9Co0.1Al2O4 solid solution is prepared by the gelcasting-foam method using notably mono- and di-functional acrylate monomers. Using a surfactant in the alkylpolyglucoside family allows to prevent structure changes in the foam before the onset of polymerisation. The wet ceramic foam is dried in air, producing a foam with an open porosity. Total porosity is equal to about 98% and the diameter of the pores is in the range 25–300 mm, about 90% being smaller than 200 mm. The Mg0.9Co0.1Al2O4 foam is reduced in H2–CH4 atmosphere, giving rise to a CNTs–Co MgAl2O4 composite foam. Using the foam instead of the corresponding powder allows a fourfold increase in the production of carbon nanotubes, more than 95% of which have only 1 (70%) or 2 walls

Inborn errors of immunity to infection: the rule rather than the exception

The immune system's function is to protect against microorganisms, but infection is nonetheless the most frequent cause of death in human history. Until the last century, life expectancy was only ∼25 years. Recent increases in human life span primarily reflect the development of hygiene, vaccines, and anti-infectious drugs, rather than the adjustment of our immune system to coevolving microbes by natural selection. We argue here that most individuals retain a natural vulnerability to infectious diseases, reflecting a great diversity of inborn errors of immunity

Human Mannose-binding Lectin in Immunity: Friend, Foe, or Both?

Human mannose-binding lectin (MBL) recognizes a wide range of microorganisms and triggers the most ancient pathway of complement activation. However, ∼5% of individuals lack functional serum MBL and have not been found to be prone to severe infections in prospective studies. These data suggest that human MBL is largely redundant for protective immunity and may even have been subject to counter selection because of a deleterious impact

Influence of the composition of a H2-CH4 gas mixture on the catalytic synthesis of carbon nanotubes-Fe/Fe3C-Al2O3 nanocomposite powders

CNTs–Fe/Fe3C–Al2O3 nanocomposite powders have been prepared by selective reduction of an a-Al1.9Fe0.1O3 solid solution in H2–CH4 gas mixtures (0, 1.5, 3, 4.5, 6, 9, 12, 14, 16, 18, 24, 30 and 45 mol% CH4). The powders have been studied using macroscopic and microscopic techniques. The CNTs are arranged in very long bundles homogeneously dispersed in the composite powder. Most CNTs have less than four walls and are free of pyrolytic or amorphous carbon deposits. The inner diameter is in the range 1–6 nm, which could indicate that the catalyst particles active for CNTs formation are in this size range. The reduction of the Fe3+ ions to metallic Fe is highly favoured by the presence of CH4 in the reduction atmosphere. There are more Fe3C than a-Fe particles located at the surface of the matrix grains for CH4 contents higher than 4.5 mol%, however, the exact nature of the catalytically active particles remains an open question. Compositions in the range 9–18 mol% CH4 give the best

Synthesis of carbon nanotube–Fe-Al2O3 nanocomposite powders by selective reduction of different Al1.8Fe0.2O3 solid solutions

Al1.8Fe0.2O3 solid solutions have been prepared as amorphous, η (cubic) and α (corundum) phases. The oxides have been reduced in a H2–CH4 gas mixture at 900 or 1000 °C, giving rise to composite powders containing alumina, α- and γ-Fe, Fe3C and different forms of carbon including nanotubes, thick tubes and spheroidal particles. The powders have been investigated using a combination of chemical analysis, X-ray diffraction, Mössbauer spectroscopy, scanning and transmission electron microscopy, thermogravimetric analysis and specific surface area measurements. Using the stable form (corundum) of Al1.8Fe0.2O3 as starting material favours the formation of carbon nanotubes compared to the other forms of carbon. This could partly result from the fact that the metal nanoparticles formed upon reduction of the α solid solution, which act as a catalyst for CH4 decomposition and possibly nanotube nucleation, are smaller than when using amorphous or η solid solutions. Moreover, the crystallization of these latter compounds during the reduction in some way provokes the entrapment of carbon within the oxide grains. The nanotubes, most of which are less than 10 nm in diameter, are arranged in bundles several tens of micrometers long

Tuberculosis in children and adults: two distinct genetic diseases

Disseminated disease in children and pulmonary disease in adults constitute two major epidemiological and clinical forms of tuberculosis. Paradoxically, only a small fraction of infected individuals develop clinical tuberculosis, typically one form of the disease or the other. Mendelian and complex genetic predispositions to tuberculosis were reported recently in children and adults, respectively. Here, we argue that tuberculosis and its clinical expression largely reflect the underlying human genetic background

Synthesis of single-walled carbon nanotube–Co–MgO composite powders and extraction of the nanotubes

A carbon nanotube-Co-MgO composite powder is prepared by reducing a Mg0.9Co0.1O solid solution in H2-CH4 atmosphere. The oxide matrix and part of the Co catalyst are dissolved by acid treatment without damage to the nanotubes. More than 80% of the carbon nanotubes have either one or two walls. The diameters of the nanotubes are in the range 0.5-5 nm. The utilized method may be a real improvement in the low-cost, large-scale synthesis of single- and double-walled carbon nanotubes

Zirconia–spinel composites. Part II: mechanical properties

The mechanical properties (fracture strength, fracture toughness, and Vickers microhardness) of MgAl2O4 and x wt% ZrO2–MgAl2O4 (1 # x # 30) hot-pressed materials were measured at room temperature. Two kinds of materials, which were prepared from either ball-milled or attrited powders, were investigated. Compared with an unreinforced spinel, a twofold (or greater) increase in both strengthening and toughening was measured for materials with the highest zirconia content (30 wt%). It was found that dispersing only 1 wt% of zirconia in the spinel produced a marked increase in the Vickers microhardness. The total zirconia content appears to be a key parameter

Zirconia-spinel composites. Part I: synthesis of powders and dense materials

MgAl2O4 and x wt% ZrO2–MgAl2O4 (1 # x # 30) composite powders were prepared by the urea combustion route. The powders were further ground by either ball milling or attrition to refine the grain size. Zirconia was found solely in the tetragonal form. Dense materials were prepared by hot pressing. The spinel matrix grains were submicronic in size. The ZrO2 particles were homogeneously dispersed at the grain junctions of the matrix, and their average size increased from less than 0.20 mm to ca. 0.45 mm with increasing content of ZrO2. The formation of monoclinic ZrO2 particles proceeded accordingly, being easier in materials with a finer matrix grain size (ex-attrition)